Next Article in Journal
Comparison of Quadratic vs. Langmuir–Hinshelwood Kinetics for Formic Acid Mineralization in a Photocatalytic Film
Next Article in Special Issue
One-Step Fe/N Co-Doping for Efficient Catalytic Oxidation and Selective Non-Radical Pathway Degradation in Sludge-Based Biochar
Previous Article in Journal
Faster Microwave-Assisted Synthesis of Microspherical Carbons from Commercial and Biomass-Derived Carbohydrates
Previous Article in Special Issue
Construction of Sulfur-Doped and Cyanide-Modified Carbon Nitride Photocatalysts with High Photocatalytic Hydrogen Production and Organic Pollutant Degradation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 15
Issue 9
10.3390/catal15090886
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Zn0.8Cd0.2S Photocatalyst Modified with Ni(OH)2 for Enhanced Photocatalytic Hydrogen Production

by
Qianran Feng
,
Xiaoting Yu
,
Jinlian Peng
,
Siying Du
,
Liuyun Chen
,
Xinyuan Xu
and
Tongming Su
*
Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China
*
Author to whom correspondence should be addressed.
Catalysts 2025, 15(9), 886; https://doi.org/10.3390/catal15090886
Submission received: 17 July 2025 / Revised: 22 August 2025 / Accepted: 12 September 2025 / Published: 15 September 2025
(This article belongs to the Special Issue Environmentally Friendly Catalysis for Green Future)
Browse Figures
Versions Notes

Abstract

Sustainable production of hydrogen is currently a global research hotspot. In this study, a Ni(OH)2 cocatalyst was loaded on Zn0.8Cd0.2S to form Ni(OH)2/ZCS composites and achieve highly efficient photocatalytic hydrogen production. After Ni(OH)2 loading, a close contact interface was established between Ni(OH)2 and Zn0.8Cd0.2S, which increased the separation efficiency of the photogenerated electrons and holes. Moreover, the addition of Ni(OH)2 increases the specific surface area and light absorption of Ni(OH)2/Zn0.8Cd0.2S, and the Ni(OH)2 can act as active sites for photocatalytic hydrogen production. The photocatalytic H2 production rate of Ni(OH)2/ZCS composites increases with the increase in the Ni amount. 9Ni(OH)2/ZCS exhibited the optimum H2 production rate of 12.88 mmol h−1 g−1, which was 9.9 times higher than that of Zn0.8Cd0.2S. When the amount of Ni(OH)2 is further increased, the excess Ni(OH)2 covers the active site of Zn0.8Cd0.2S and reduced the light absorption of Zn0.8Cd0.2S, resulting in a decrease in the H2 production rate. Furthermore, the H2 production rate of 9Ni(OH)2/ZCS decreased from 12.88 to 5.15 mmol g−1 h−1 after 3 cycles. The main reason for the decline in the photocatalytic performance of Ni(OH)2/ZCS is the photocorrosion of Zn0.8Cd0.2S. This study provides an innovative design for loading Ni(OH)2 cocatalysts on Zn0.8Cd0.2S to improve the performance of photocatalysts.

1. Introduction

In recent years, global energy scarcity and environmental pollution caused by the burning of fossil fuels have become increasingly serious problems [1,2]. Therefore, there is an urgent need to find a clean energy source [3,4]. Hydrogen, as an ideal clean energy source, is an alternative to fossil energy sources [5]. Among the various methods of hydrogen production, the use of solar energy to produce hydrogen is regarded as a promising strategy [6,7]. Since 1972, when Professors Fujishima A and Honda K discovered that TiO2 possesses photocatalytic activity [8], researchers have developed various semiconductor photocatalysts, such as metal sulfides, (oxy)nitrides, and metal oxides, in recent decades [9,10,11,12].
Among the various types of metal sulfides, ZnCdS is a typical ternary sulfide that has wide spectral absorption and appropriate redox potentials [13,14]. Previous studies have shown that the separation efficiency of photoelectrons and holes is greatly improved when the Zn/Cd molar ratio is 0.8:0.2 [14]. Compared with other Zn(1−x)CdxS materials, Zn0.8Cd0.2S has more surface defect states, which can serve as active sites to improve the performance of photocatalytic hydrogen production. Moreover, the photocatalytic hydrogen production efficiency of Zn0.8Cd0.2S is much greater than that of ZnS and CdS under visible light [15]. However, the fast recombination of photoexcited charge carriers and severe photocorrosion limit their photocatalytic activity [16,17]. The addition of suitable cocatalysts is an effective means to improve the performance and stability of Zn0.8Cd0.2S in photocatalytic hydrogen production reactions [18].
Noble metals, such as Pt, Pd, Ag, and Au, have been widely used to improve the performance of photocatalytic hydrogen production. However, most noble metal cocatalysts are scarce and expensive. To reduce the cost of photocatalytic hydrogen production, finding alternative cocatalysts to replace precious metals has become a popular research topic. More recently, researchers have reported that Ni-based cocatalysts have the advantages of low cost, easy access, and high stability and can be used as ideal cocatalysts for photocatalysts [19,20,21]. For example, Lei et al. prepared a NiS@ZnCdS z-scheme heterostructure via a hydrothermal method, which enhances the separation of photogenerated electron–hole pairs and increases the photocatalytic activity [22]. In addition, Pan et al. prepared Zn0.3Cd0.7S/NiS1.97 nanocomposites [23], in which NiS1.97 nanosheets are tightly coupled to the inner surface of Zn0.3Cd0.7S hollow spheres as cocatalysts. The hollow spherical shell structure decreases the distance of charge transfer to the surface, promotes the absorption of incident light, and significantly improves the photocatalytic hydrogen production performance [24,25].
However, the photocatalytic performance of ZnCdS is still relatively low; therefore, more Ni-based cocatalysts need to be developed to increase the stability and activity of the photocatalysts [26,27]. In recent years, Ni(OH)2 has received widespread attention because of its low cost, high stability, and simple preparation method. According to previous reports, Ni(OH)2 loaded on photocatalysts can efficiently inhibit the recombination of photogenerated electrons and holes, making it a promising noble metal-free cocatalyst [28,29]. Moreover, the formation of an interface between the Ni(OH)2 cocatalyst and the photocatalyst is utilized to facilitate charge carrier separation, and the Ni(OH)2 cocatalyst can also be used as an active site for surface reactions [29]. For example, the photocatalytic hydrogen evolution rate of a Ni(OH)2-modified two-dimensional ZnIn2S4 heterostructure reached 4640 μmol h−1 g−1 under visible light irradiation (λ > 420 nm) [30], which can be attributed to the synergistic effect between Ni(OH)2 and ZnIn2S4. Compared with those on pristine ZnIn2S4, the assembled β-Ni(OH)2 nanosheets on the surface of exfoliated ZnIn2S4 nanosheets significantly promoted charge separation, water oxidation kinetics, and photocatalytic performance [31,32].
Although Ni(OH)2 has been widely researched as a co-catalyst for photocatalytic H2 production, its practical application is still limited by the low photocatalytic efficiency. The morphology, proportion, and contact interface in Ni(OH)2-based composite photocatalysts are the key factors influencing the H2 production rate. In this work, Ni(OH)2 nanosheets were successfully loaded on Zn0.8Cd0.2S nanospheres by a simple method. The influence of the Ni(OH)2 content on the photocatalytic activity of Zn0.8Cd0.2S was investigated. Under visible light irradiation, the H2 production rate of 9Ni(OH)2/ZCS is significantly higher than that of other Ni(OH)2-based photocatalysts. In addition, the mechanism of photogenerated carrier transfer between Ni(OH)2 and Zn0.8Cd0.2S was revealed, and a mechanism for photocatalytic hydrogen production over Ni(OH)2/Zn0.8Cd0.2S composites was proposed.

2. Results and Discussion

The XRD patterns of Zn0.8Cd0.2S, Ni(OH)2, and the Ni(OH)2/ZCS composite are shown in Figure 1a. The peaks at 27.3°, 28.7°, and 30.7° in the XRD patterns of Zn0.8Cd0.2S can be attributed to the (100), (002), and (101) crystal planes of Zn0.8Cd0.2S, respectively [14]. The position of these peaks of Zn0.8Cd0.2S is completely consistent with the standard wurtzite structure, which confirms that the synthesized material has a typical hexagonal wurtzite crystal structure [33]. The diffraction peaks at 19.1°, 33.0°, 38.8°, 51.9°, 59.0°, and 62.6° can be attributed to the (001), (100), (011), (012), (110), and (111) crystal planes of β-Ni(OH)2, respectively [34]. According to Equation (1), the Coherent Scattering Domain (CSD) size of Zn0.8Cd0.2S and Ni(OH) is 13.7 and 4.34 nm, respectively.
C S D = K λ β c o s θ
where K is the shape factor (value is 0.9), λ is the X-ray wavelength, and β is the full width at half maximum of the diffraction peak, θ is the diffraction angle.
After loading Ni(OH)2 on the surface of Zn0.8Cd0.2S, the XRD peak of the Ni(OH)2/ZCS composite catalyst was consistent with that of the original Zn0.8Cd0.2S, indicating that β-Ni(OH)2 did not change the structure of Zn0.8Cd0.2S. When the loading content of Ni(OH)2 was greater than 5 wt%, the Ni(OH)2/ZCS composites presented a weak diffraction peak at 38.8°, which was attributed to the (011) plane of Ni(OH)2 [9]. These results confirm the successful synthesis of the Ni(OH)2/ZCS composites.
The FT-IR spectra of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites are shown in Figure 1b. The broad peak at 3430 cm−1 corresponded to the bending vibration of O-H, and the peak at 1630 cm−1 was attributed to the stretching vibration of O-H, which was derived from the water absorbed on the photocatalyst surface. The peak at 3640 cm−1 is attributed to the stretching vibration mode of nonhydrogen-bonded hydroxyl groups in Ni(OH)2, indicating that the hydroxyl groups in Ni(OH)2 were arranged freely and existed in the form of β-Ni(OH)2 [35], which was consistent with the XRD results. Notably, there were peaks at 3640 cm−1 in the Ni(OH)2/ZCS composite, indicating the presence of Ni(OH)2 in the composite. The absorption peak of Ni(OH)2 at 1383 cm−1 corresponded to the vibration of the interlayer NO3−, which originated from nitrate during the preparation process. Moreover, Ni(OH)2 and Ni(OH)2/ZCS have two infrared peaks at 526 cm−1 and 456 cm−1, which are attributed to the Ni–O stretching vibration in β-Ni(OH)2 and the bending vibration of Ni–O–H [36], respectively. The above results further indicate the successful synthesis of the Ni(OH)2/ZCS composites.
N2 adsorption–desorption isotherms of the Ni(OH)2/ZCS composites are shown in Figure S1a. Figure S1a shows that the N2 adsorption–desorption isotherms of the Ni(OH)2/ZCS composites and Zn0.8Cd0.2S are type IV. The pore size distribution curve in Figure S1b shows that the pore size distributions of the Zn0.8Cd0.2S and Ni(OH)2/ZCS composites range from 1~5 nm. The specific surface area and average pore size of the Zn0.8Cd0.2S and Ni(OH)2/ZCS composites are shown in Table S1. The specific surface area of the Ni(OH)2/ZCS composites was slightly greater than that of Zn0.8Cd0.2S. The specific surface areas of Zn0.8Cd0.2S, 1Ni(OH)2/ZCS, 5Ni(OH)2/ZCS, 9Ni(OH)2/ZCS, and 13Ni(OH)2/ZCS were 204.6, 204.9, 209.2, 212.4, and 212.8 m2 g−1, respectively. Notably, the specific surface area of the Ni(OH)2/ZCS composites gradually increased with increasing Ni(OH)2 content. In general, an increase in the specific surface area of a photocatalyst can provide more surface active sites, which is beneficial for photocatalytic hydrogen production. In addition, the average pore size of the Ni(OH)2/ZCS composites (~3 nm) was slightly greater than that of Zn0.8Cd0.2S (2.81 nm), indicating that the addition of Ni(OH)2 can regulate the pore structure of the Ni(OH)2/ZCS composites.
The morphologies of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites were characterized by scanning electron microscopy (SEM). As shown in the SEM images of Zn0.8Cd0.2S (Figure 2a), Zn0.8Cd0.2S has a microsphere shape with a diameter of approximately 100 nm. In addition, the surface of the Zn0.8Cd0.2S nanospheres was rough, with small nanoparticles uniformly distributed on the surface. As shown in Figure 2b, Ni(OH)2 has a nanosheet structure. The SEM images of the Ni(OH)2/ZCS composites (Figure 2c–f) are similar to those of the Zn0.8Cd0.2S nanospheres, and no Ni(OH)2 nanosheets can be clearly observed in the Ni(OH)2/ZCS composites, indicating that the Ni(OH)2 nanosheets were uniformly distributed on the surface of the small Zn0.8Cd0.2S nanospheres.
Figure 3a confirmed that the Zn0.8Cd0.2S nanospheres consisted of small nanoparticles. Figure 3b shows that the lattice fringe spacings of 0.31 nm and 0.19 nm are attributed to the (002) and (110) crystal planes of hexagonal Zn0.8Cd0.2S, respectively. The TEM images of Ni(OH)2 (Figure 3d,e) further confirmed the nanosheet shape of Ni(OH)2, and the lattice fringes of 0.23 and 0.46 nm were attributed to the (011) and (001) crystal planes of β-phase Ni(OH)2, respectively [37]. Figure 3c,f show that the diffraction rings of the Zn0.8Cd0.2S and Ni(OH)2 samples correspond to the (100) and (110) crystal planes of Zn0.8Cd0.2S and the (011) and (004) crystal planes of Ni(OH)2, respectively. The above results indicated that Zn0.8Cd0.2S and Ni(OH)2 were successfully prepared.
The TEM, SAED, and EDS element distribution maps of 9Ni(OH)2/ZCS are shown in Figure 4. After the 9Ni(OH)2/ZCS composite was synthesized, the morphology of the nanospheres was still maintained, and several 9Ni(OH)2 nanosheets were observed on the surface of the nanospheres (Figure 4a). As shown in the HRTEM images of 9Ni(OH)2/ZCS (Figure 4b), the lattice spacings of 0.32 and 0.23 nm correspond to the (100) crystal plane of Zn0.8Cd0.2S and the (011) crystal plane of Ni(OH)2, respectively, indicating that close contact interfaces formed between Ni(OH)2 and Zn0.8Cd0.2S. In addition, two diffraction rings in the SAED patterns (Figure 4c) of 9Ni(OH)2/ZCS correspond to the (100) plane of Zn0.8Cd0.2S and the (012) plane of Ni(OH)2. The EDS results (Figure 4d) corresponding to the HAADF-STEM image show that Zn, Cd, S, Ni, and O were evenly distributed in the 9Ni(OH)2/ZCS sample. The above results show that the 9Ni(OH)2/ZCS composite was successfully constructed.
To reveal the valence state of the elements in the Ni(OH)2/ZCS composites, the surface chemical states of the Zn0.8Cd0.2S, Ni(OH)2, and 9Ni(OH)2/ZCS composites were analyzed via XPS (Figure 5). As shown in Figure 5a, the XPS survey spectra of 9Ni(OH)2/ZCS reveal that Zn, Cd, S, Ni, and O are present in 9Ni(OH)2/ZCS. As shown in Figure 5b–d, the peaks of Zn 2p (1045.31 and 1022.31 eV), Cd 3d (411.89 and 405.17 eV), and S 2p (163.10 and 161.85 eV) of Zn0.8Cd0.2S were attributed to Zn2+, Cd2+, and S2− [38], respectively. Compared with those of Zn0.8Cd0.2S, the XPS peaks of Zn 2p, Cd 3d, and S 2p in 9Ni(OH)2/ZCS shifted to higher binding energies. Zn 2p1/2 and Zn 2p3/2 shifted to 1045.37 and 1022.41 eV, Cd 3d3/2 and Cd 3d5/2 shifted to 412.11 and 405.38 eV, and S 2p1/2 and S 2p3/2 shifted to 163.43 and 162.08 eV, respectively.
The high-resolution XPS spectra of Ni 2p are shown in Figure 5e. The binding energies of Ni 2p1/2 and Ni 2p3/2 of Ni(OH)2 were located at 873.71 and 856.26 eV, respectively, and two adjacent peaks at 879.92 and 861.90 eV were attributed to satellite peaks [39]. Notably, the Ni 2p peak of 9Ni(OH)2/ZCS was located at 873.61 and 856.21 eV, which shifted to lower binding energies by 0.1 and 0.05 eV, respectively, than that of Ni(OH)2. As shown in Figure 5f, the O 1 s peaks of 9Ni(OH)2/ZCS exhibit two peaks at 533.54 and 532.07 eV, which are attributed to hydroxide and water adsorbed on the surface, respectively. Compared with the O 1s peak of Ni(OH)2 (533.39 and 531.58 eV), the O 1s peak of 9Ni(OH)2/ZCS shifted to higher binding energies by 0.15 and 0.49 eV. These results revealed that there is a strong interaction between Ni(OH)2 and Zn0.8Cd0.2S composites and that the electron can transfer from Zn0.8Cd0.2S to Ni(OH)2 after Ni(OH)2 contacts Zn0.8Cd0.2S. In addition, in Ni(OH)2, electrons gather at the Ni site, which might be the active site for photocatalytic hydrogen production.
The light absorption of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites was analyzed via UV–vis diffuse reflectance spectroscopy. As shown in Figure 6a, the UV–vis diffuse reflectance spectra of Ni(OH)2 show strong absorption in the range of 230~800 nm [40]. Notably, the absorption at 600~800 nm of the Ni(OH)2/ZCS composites gradually increased with increasing content of Ni(OH)2. Notably, the absorption edge of the Ni(OH)2/ZCS did not shift, indicating that Ni(OH)2 did not change the band structure of Zn0.8Cd0.2S. In addition, the band gap of Zn0.8Cd0.2S was estimated to be 2.65 eV (Figure 6b).
The separation efficiencies of the photogenerated charge carriers of the Zn0.8Cd0.2S and Ni(OH)2/ZCS composites were investigated via PL spectra [41]. Figure 7a shows that the PL intensity of the Ni(OH)2/ZCS composites was significantly lower than that of Zn0.8Cd0.2S, indicating that the loading of Ni(OH)2 on the surface of Zn0.8Cd0.2S effectively inhibited the recombination of photogenerated electrons and holes. TRPL spectra were used to further analyze the separation of photogenerated electrons and holes. As shown in Figure 7b, the average fluorescence lifetime of 9Ni(OH)2/ZCS was 5.19 ns, which was longer than that of Zn0.8Cd0.2S (4.37 ns), further demonstrating that the Ni(OH)2 cocatalyst can effectively inhibit the recombination of photogenerated electrons and holes [42].
To further clarify the separation of the photogenerated electrons and holes in the catalyst, the photoelectrochemical properties of Zn0.8Cd0.2S and 9Ni(OH)2/ZCS were investigated. As shown in Figure 7c, the transient photocurrent of 9Ni(OH)2/ZCS was significantly greater than that of Zn0.8Cd0.2S, indicating that the separation of photogenerated charge carriers was enhanced by the addition of the Ni(OH)2 cocatalyst. In addition, to study the electron transfer resistance of the catalyst, the EIS data of Zn0.8Cd0.2S and 9Ni(OH)2/ZCS were obtained. As shown in Figure 7d, the arc radius of 9Ni(OH)2/ZCS was smaller than that of Zn0.8Cd0.2S, indicating that the charge transfer resistance in 9Ni(OH)2/ZCS was lower. The above analysis indicates that the loading of Ni(OH)2 on Zn0.8Cd0.2S promoted the separation of photogenerated electrons and holes, which is beneficial for the photocatalytic hydrogen production reaction.
The performance of the photocatalysts for photocatalytic hydrogen production under visible light (λ > 400 nm) was investigated with Na2S (0.35 M)/Na2SO3 (0.25 M) mixed aqueous solutions as sacrificial agents. As shown in Figure 8a and Figure S2, the photocatalytic H2 production rate of Zn0.8Cd0.2S was 1.30 mmol h−1 g−1. After Ni(OH)2 was loaded on Zn0.8Cd0.2S, the H2 production rate significantly increased. When the Ni(OH)2 content was 9 wt%, the H2 production rate of 9Ni(OH)2/ZCS reached the highest value of 12.88 mmol h−1 g−1, which was 9.9 times greater than that of Zn0.8Cd0.2S. However, when the Ni(OH)2 content increased to 13 wt%, the H2 production rate decreased to 12.30 mmol h−1 g−1, possibly because excessive Ni(OH)2 covered the surface of Zn0.8Cd0.2S and reduced the light absorption of Zn0.8Cd0.2S. Notably, no H2 product can be detected over Ni(OH)2 after photocatalytic reaction for 4 h, indicating that Ni(OH)2 only acts as a cocatalyst of Zn0.8Cd0.2S to enhance its photocatalytic performance. The performance comparison is shown in Table S2. The H2 production rate of 9Ni(OH)2/ZCS is significantly higher than that of other reported photocatalysts. In pure water, 9Ni(OH)2/ZCS exhibits a low photocatalytic H2 production rate of 49.86 µmol·g−1·h−1. The extremely low H2 production efficiency of photocatalytic overall water splitting severely hinders its practical application. Constructing heterojunctions and redox-active sites can promote the separation of photogenerated electron-hole pairs and the hydrogen/oxygen evolution, thereby achieving efficient photocatalytic overall water splitting. In addition, the catalytic performances normalized on surface area and mass are shown in Table S3. 9Ni(OH)2/ZCS shows the highest H2 production rate normalized on surface area or mass.
To reveal the utilization efficiency of optical energy, the apparent quantum yield (AQY) of 9Ni(OH)2/ZCS at different wavelengths (380 nm, 400 nm, 420 nm, and 450 nm) was tested. As shown in Figure 8b, the AQYs of 9Ni(OH)2/ZCS are 17.03%, 3.51%, 1.25%, and 0.64% at 380 nm, 400 nm, 420 nm, and 450 nm, respectively. On the basis of our previous research on Zn0.8Cd0.2S [14], the AQY of 9Ni(OH)2/ZCS at 400 nm was greater than that of Zn0.8Cd0.2S (2.05%), which demonstrated that the addition of the Ni(OH)2 cocatalyst significantly improved the utilization of visible light by Zn0.8Cd0.2S.
To evaluate the reusability of the 9Ni(OH)2/ZCS photocatalysts, cyclic experiments were carried out on 9Ni(OH)2/ZCS. As shown in Figure S2b, after 3 cycles, the stability of 1Ni(OH)2/ZCS, 5Ni(OH)2/ZCS, 9Ni(OH)2/ZCS, and 13Ni(OH)2/ZCS decreased by 59.84%, 58.71%, 58.13%, and 62.09%, respectively. After 5 cycles, the stability of 1Ni(OH)2/ZCS, 5Ni(OH)2/ZCS, 9Ni(OH)2/ZCS, and 13Ni(OH)2/ZCS decreased by 82.12%, 78.25%, 74.11%, and 78.67%, respectively. To determine the reason for the decrease in hydrogen production, the sacrificial agent was supplemented in the sixth cycle of the reaction. After the addition of the sacrificial agent, the H2 production rate of 9Ni(OH)2/ZCS only slightly improved. This result indicated that the main reason for the decrease in the H2 production rate of 9Ni(OH)2/ZCS was not the consumption of sacrificial agents.
To further investigate the stability of 9Ni(OH)2/ZCS, 9Ni(OH)2/ZCS after the reaction was characterized via XRD, XPS, SEM, and TEM. As shown in Figure S3a, the XRD patterns of the 9Ni(OH)2/ZCS photocatalyst before and after the reaction indicated that the crystal structure of 9Ni(OH)2/ZCS was stable. The CSD size of 9Ni(OH)2/ZCS is 12.76 nm, which is similar to that of 9Ni(OH)2/ZCS before reaction (13.58 nm) and Zn0.8Cd0.2S (13.70 nm). However, the high-resolution XPS spectra of 9Ni(OH)2/ZCS after the reaction (Figure S3b–f) revealed that the XPS peaks of Zn 2p, Cd 3d, S 2p, and O 1s in 9Ni(OH)2/ZCS shifted to higher binding energies, whereas the XPS peaks of Ni 2p shifted to lower binding energies. That is, the electronic structure of 9Ni(OH)2/ZCS changed after the reaction, which may be attributed to the photocorrosion of Zn0.8Cd0.2S. In addition, as shown in Figure S4a, SEM images of 9Ni(OH)2/ZCS after the reaction revealed that 9Ni(OH)2/ZCS still maintained the nanosphere morphology after the reaction. Moreover, the Ni(OH)2 nanosheet can still be observed in the TEM image (Figure S4b). In Figure S4c, the (002) plane of Zn0.8Cd0.2S and the (011) plane of Ni(OH)2 can be observed in the HRTEM image of 9Ni(OH)2/ZCS after the reaction. Moreover, the element mapping corresponding to the HAADF-STEM image (Figure S4c) shows that Zn, Cd, S, Ni, and O were uniformly distributed in 9Ni(OH)2/ZCS. The above results demonstrated that the composition and structure of 9Ni(OH)2/ZCS remain unchanged after the reaction, and the possible reason for the decreased photocatalytic performance of 9Ni(OH)2/ZCS might be the photocorrosion of Zn0.8Cd0.2S. To enhance the stability of Ni(OH)2/ZCS, some potential strategies are believed to effectively prevent the photocorrosion of Zn0.8Cd0.2S. Firstly, the photogenerated holes on Zn0.8Cd0.2S transfer or consumption via a reasonable heterojunction (e.g., S-scheme heterojunction, Z-scheme heterojunction, etc.). Secondly, anchoring photo-oxidation active sites (e.g., CoOx, MnOx, etc.) accelerates the photocatalytic oxidation reaction and the consumption of photogenerated holes. Finally, constructing core–shell structures (e.g., surface passivation layers, shell structures) restricts the detachment of S.
From Figure 9a, the Ecutoff value of Zn0.8Cd0.2S is 7.71 eV. According to Equations (2)–(4), the work function of Zn0.8Cd0.2S is calculated as 3.51 eV, and the Fermi level of Zn0.8Cd0.2S is determined to be −3.51 eV (vs. vacuum level). Furthermore, the VB potential of Zn0.8Cd0.2S is determined to be 1.80 eV (vs. Fermi level), which is converted to −5.31 eV (vs. vacuum level). Combined with the bandgap, the CB potential of Zn0.8Cd0.2S is derived via Equation (5) as −2.66 eV (vs. vacuum level). The energy level structure of Zn0.8Cd0.2S is shown in Figure 9b.
ϕ = h v − E c u t o f f
E F = E v a c − ϕ
E VB = E F − E VB ( v s   Fermi   level )
E g = E C B − E V B
Combining the above results, a possible mechanism for photocatalytic hydrogen production over Ni(OH)2/ZCS composites was proposed. As shown in Figure 10, the electrons in the valence band (VB) of Zn0.8Cd0.2S were stimulated to the conduction band (CB) under visible light. The photogenerated electrons of Zn0.8Cd0.2S can then transfer to Ni(OH)2 through the close contact interfaces between Zn0.8Cd0.2S and Ni(OH)2. Moreover, the photogenerated electrons can rapidly migrate to the surface of Ni(OH)2, and Ni(OH)2 can act as the active site for reducing H+ to H2. In addition, the photogenerated holes in the valence band of Zn0.8Cd0.2S are consumed by the hole sacrificial agent, which effectively promotes the separation of photogenerated electrons and holes. Thus, the photocatalytic H2 production performance of the Ni(OH)2/ZCS composites was greatly improved.

3. Experimental Section

3.1. Materials

All the chemicals used during the experiments were of analytical grade and were used without further purification and processing. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O, Damao Chemical Reagent Factory, Tianjin, China, >99%), cadmium acetate dihydrate (Cd(CH3COO)2·2H2O, Komeo Chemical Reagent Co., Ltd., Tianjin, China, >99.5%), polyvinylpyrrolidone ((C6H9NO)n, PVP, Shanghai Aladdin Biochemical Technology Co., Ltd., Shanghai, China, Mr = 1,300,000), thiourea (CH4N2S, Guanghua Sci-Tech Co., Ltd., Shantou, China, >99%), sodium sulfide nonahydrate (Na2S·9H2O, Xilong Scientific Co., Ltd., Shantou, China, >98%), sodium sulfite (Na2SO3, Xilong Scientific Co., Ltd., Shantou, China, >97%), nickel nitrate (Ni(NO3)2, Komeo Chemical Reagents Ltd., Tianjin, China, >99%), nickel nitrate (NaOH, Komeo Chemical Reagents Ltd., Tianjin, China, >98%), ethylene glycol ((CH2OH)2, Kemao Chemical Reagent Co., Ltd., Tianjin, China, >99%), triethanolamine (C6H15NO3, Xilong Scientific Co., Ltd., Shantou, China, ≥98%), methanol (CH4O, Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, ≥99.5%), lactic acid (CH3CH(OH)COOH, Tianjin Fuyu Fine Chemical Co., Ltd., Tianjin, China, 85.0–90.0%).

3.2. Synthesis of Zn0.8Cd0.2S

1.2 mmol of Cd(CH3COO)2·2H2O and 4.8 mmol of Zn(CH3COO)2·2H2O were dissolved in 60 mL of ethylene glycol while stirring, and then, 1.08 g of PVP and 7.5 mmol of CH4N2S were added to the solution. The above solution was subsequently transferred to a 100 mL stainless steel high-pressure reactor with Teflon lining, which was heated at 180 °C and maintained for 12 h. After the reactants cooled, the obtained precipitates were centrifuged and washed 5 times with deionized water and anhydrous ethanol. After that, the precipitate was dried in an oven at 60 °C for 12 h, and Zn0.8Cd0.2S was obtained.

3.3. Synthesis of Ni(OH)2

1.9 g of Ni(NO3)2 was dissolved in 30 mL of deionized water, and 15 mL of 5 M Ni(OH)2 solution was added to it while stirring. The solution was stirred for 1.5 h, centrifuged, washed 8 times with deionized water, and placed in a vacuum drying oven. The temperature was raised to 60 °C and maintained for 12 h to obtain Ni(OH)2.

3.4. Synthesis of Ni(OH)2/ZCS

Zn0.8Cd0.2S (200 mg) was dispersed in 30 mL of deionized water, and 108 μL of 2 M Ni(NO3)2 solution was added and stirred evenly. The solution was ultrasonically dispersed for 20 min, 3 mL of 5 M NaOH was added dropwise while stirring, and the mixture was stirred for 5.5 h. After the reaction, the mixture was centrifuged to obtain the precipitate, which was then washed with deionized water until the supernatant was neutral. After that, the precipitate was placed in a vacuum drying oven at 60 °C and maintained for 12 h to obtain Ni(OH)2/Zn0.8Cd0.2S composites with a mass fraction of 1% Ni(OH)2, labeled 1Ni(OH)2/ZCS. When the amount of added Ni(NO3)2 solution was changed, Ni(OH)2/ZCS composites with different amounts (5 wt%, 9 wt%, and 13 wt%) of Ni(OH)2 were obtained, labeled 5Ni(OH)2/ZCS, 9Ni(OH)2/ZCS, and 13Ni(OH)2/ZCS, respectively.

3.5. Characterization of the Catalysts

The crystal structure of the catalyst was examined by X-ray diffraction (XRD) using a Rigaku SMARTLAB 3KW diffractometer (Tokyo, Japan, Cu Kα radiation). Fourier-transform infrared (FT-IR) spectroscopy was conducted on a Bruker TENSOR II spectrometer (Bremen, Germany) to investigate chemical bonding. Morphological analysis was performed using a Carl Zeiss Sigma 300 field-emission scanning electron microscope (FE-SEM, Oberkochen, Germany) operated at 10 kV acceleration voltage. For detailed crystallographic analysis, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), high-angle annular dark-field scanning TEM (HAADF-STEM), and elemental mapping were carried out using a Thermo Fisher Scientific Talos F200X TEM (Santa Clara, CA, USA). N2 adsorption–desorption isotherms were measured with a Micromeritics TriStar II analyzer (Norcross, GA, USA) to determine the specific surface area and pore size distribution. Surface chemical states were analyzed by X-ray photoelectron spectroscopy (XPS, Thermo Scientific, Waltham, MA, USA) on a Thermo Fisher Scientific K-Alpha spectrometer. Steady-state photoluminescence (PL, Thermo Fisher Scientific, USA) spectra were recorded on a Thermo Fisher Lumina fluorescence spectrometer, while time-resolved fluorescence decay was measured using an Edinburgh Instruments FLS 1000 spectrometer (Edinburgh, UK, excitation: 365 nm laser). Optical absorption properties were evaluated via UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) using a Beijing General Instrument TU-19 spectrophotometer (Beijing, China) equipped with an IS19-1 integrating sphere. Ultraviolet photoelectron spectroscopy (UPS) was performed on a PHI5000 Versa Probe III system (ULVAC-PHI, Inc., Fujisawa-shi, Japan, equipped with a spherical analyzer) to determine the surface work function and electronic structure.

3.6. Photoelectrochemical Measurements

The photoelectrochemical experiments were conducted using a CHI760E electrochemical workstation with a standard three-electrode system (Shanghai Chenhua Instrument Co., Ltd., Shanghai, China). The system consisted of a reference electrode (Ag/AgCl), a counter electrode (Pt mesh), and a working electrode (photocatalyst). A 0.5 M Na2SO4 solution serves as the electrolyte. 20 mg of photocatalyst was added to 400 μL anhydrous ethanol with 20 μL Nafion solution, followed by 90 min ultrasonication to achieve homogeneous dispersion. Subsequently, 0.1 mL of the suspension was uniformly drop-cast onto a 1 cm × 1 cm FTO substrate and dried at room temperature. A 300 W xenon lamp with a 400 nm cut-off filter is used as the light source. Electrochemical impedance spectroscopy (EIS) was tested at an alternating amplitude of 5 mV and a frequency of 0.01 Hz–1000 kHz.

3.7. Photocatalytic Hydrogen Evolution

The hydrogen production performance was evaluated in a 167 mL top-irradiation quartz reactor. A 300 W xenon lamp (CEL-HXF300-T3, Beijing China Education Au-light Co., Ltd., Beijing, China) equipped with a 400 nm cut-off filter served as the light source, providing an irradiation intensity of 103 mW cm−2. The photocatalytic reaction system consisted of 20 mg photocatalyst dispersed in 50 mL of aqueous solution containing 0.35 M Na2S and 0.25 M Na2SO3 as sacrificial agents. The mixture was ultrasonicated for 10 min to ensure homogeneous dispersion. Prior to illumination, the system was purged with ultra-high purity argon for 30 min to eliminate air. Subsequently, the suspension was continuously stirred during the reaction, and the temperature of the reactor was maintained at 25 °C using circulating cooling water. After the reaction began, the gaseous products were quantitatively detected by gas chromatography (GC-2018, SHIMADZU, Kyoto, Japan) with argon as the carrier gas. The AQY was measured using monochromatic filters (380, 400, 420, and 450 nm) and calculated according to the following equation:
A Q Y = 2 × t h e   n u m b e r   o f   e v o l v e d   H 2   M o l e c u l e s t h e   n u m b e r   o f   i n c i d e n t   p h o t o s × 100 % = 2 × r × N A × h × c S × I × t × λ
where r is the yield of hydrogen, NA is the Avogadro constant, h is the Planck constant, c is the speed of light, S is the illumination area, I is the average optical power density, t is the illumination time, and λ is the wavelength of the monochromatic light source.
The reusability tests of the catalysts were carried out using the following experimental procedure: each cycle was carried out under visible light (λ ≥ 400 nm) for 4 h. After a single cycle reaction, the system was purged with ultra-high purity argon gas for 30 min to remove the H2 generated in the previous cycle. During the 5-cycle tests, no additional sacrificial agent was added, and the photocatalyst was not washed. To reveal the role of the sacrificial agent, 17.5 mmol Na2S and 12.5 mmol Na2SO3 were added in the sixth cycle tests.

4. Conclusions

In summary, Ni(OH)2/Zn0.8Cd0.2S composites were synthesized to increase photocatalytic hydrogen production. After loading with Ni(OH)2, close contact interfaces formed between Ni(OH)2 and Zn0.8Cd0.2S, which was beneficial for the transfer and separation of charge carriers. In addition, the addition of Ni(OH)2 increases the specific surface area, enhances light absorption, and increases the separation efficiency of the photogenerated electrons and holes of Ni(OH)2/Zn0.8Cd0.2S. The photocatalytic H2 production rate of Ni(OH)2/ZCS composites increases with the increase in the Ni amount. 9Ni(OH)2/ZCS exhibited the optimum H2 production rate of 12.88 mmol h−1 g−1, which was 9.9 times higher than that of Zn0.8Cd0.2S. When the amount of Ni(OH)2 is further increased, the excess Ni(OH)2 covers the active site of Zn0.8Cd0.2S and reduces the light absorption of Zn0.8Cd0.2S, resulting in a decrease in the H2 production rate. Furthermore, the H2 production rate of 9Ni(OH)2/ZCS decreased from 12.88 to 5.15 mmol g−1 h−1 after 3 cycles. The main reason for the decline in the photocatalytic performance of Ni(OH)2/ZCS is the photocorrosion of Zn0.8Cd0.2S. In pure water, 9Ni(OH)2/ZCS exhibits a low photocatalytic H2 production rate of 49.86 µmol·g−1·h−1. The extremely low H2 production efficiency of photocatalytic overall water splitting severely hinders its practical application. Constructing heterojunctions and redox-active sites can promote the separation of photogenerated electron-hole pairs and the hydrogen/oxygen evolution, thereby achieving efficient photocatalytic overall water splitting. The high activity of the Ni(OH)2/Zn0.8Cd0.2S composite was attributed mainly to the increased separation efficiency of photogenerated electrons and holes and the addition of Ni(OH)2 active sites. This work reveals the effects of Ni(OH)2 cocatalysts on the photocatalytic H2 production reaction, which is highly important for the development of efficient photocatalysts.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal15090886/s1, Refs. [27,28,30,43,44,45,46,47,48,49,50,51,52,53,54] are cited in Supplementary Materials.

Author Contributions

Conceptualization, T.S.; methodology, L.C. and S.D.; validation, T.S.; formal analysis, L.C. and T.S.; investigation, Q.F., X.Y., J.P., and S.D.; resources, T.S.; data curation, Q.F. and S.D.; writing—original draft, Q.F.; writing—review and editing, X.X. and T.S.; visualization, Q.F. and S.D.; supervision, T.S.; project administration, T.S.; funding acquisition, T.S. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (22208065), the Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology (2023K012), and Guangxi Students’ Innovation and Entrepreneurship Training Programs (202410593095).

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Zhong, W.; Xu, J.; Wang, P.; Zhu, B.; Fan, J.; Yu, H. Novel core-shell Ag@AgSe nanoparticle co-catalyst: In situ surface selenization for efficient photocatalytic H2 production of TiO2. Chin. J. Catal. 2022, 43, 1074–1083. [Google Scholar] [CrossRef]
  2. Wang, J.; Niu, X.; Wang, R.; Zhang, K.; Shi, X.; Yang, H.Y.; Ye, J.; Wu, Y. High-entropy alloy-enhanced ZnCdS nanostructure photocatalysts for hydrogen production. Appl. Catal. B Environ. Energy 2025, 362, 124763. [Google Scholar] [CrossRef]
  3. Huang, C.; Liu, N.; Zhou, Y.; Mao, H.; Qi, F.; Ouyang, X. Construction of 3D/0D Sv-ReS2/ZnCdS hierarchical structure with improved interfacial charge transfer for enhanced photocatalytic hydrogen evolution. Sep. Purif. Technol. 2025, 354, 128838. [Google Scholar] [CrossRef]
  4. Hiragond, C.B.; Powar, N.S.; Kim, H.; In, S.-I. Unlocking solar energy: Photocatalysts design for tuning the CO2 conversion into high-value (C2+) solar fuels. EnergyChem 2024, 6, 100130. [Google Scholar] [CrossRef]
  5. Lian, Z.; Qu, M.; Xiao, H.; Wang, L.; Wu, H.; Zi, J.; Wang, W.; Li, H. Direct Observation of Z-Scheme Route in Cu31S16/ZnxCd1-xS Heteronanoplates for Highly Efficient Photocatalytic Hydrogen Evolution. Small 2024, 20, 2400611. [Google Scholar] [CrossRef]
  6. He, J.; Chen, L.; Xie, X.; Qin, Z.; Ji, H.; Su, T. Construction of ZnCoP/CdLa2S4 Schottky Heterojunctions for Enhancing Photocatalytic Hydrogen Evolution. Acta Phys. Chim. Sin. 2024, 40, 2404030. [Google Scholar] [CrossRef]
  7. Kim, H.; Seo, J.W.; Chung, W.; Narejo, G.M.; Koo, S.W.; Han, J.S.; Yang, J.; Kim, J.Y.; In, S.I. Thermal Effect on Photoelectrochemical Water Splitting Toward Highly Solar to Hydrogen Efficiency. ChemSusChem 2023, 16, e202202017. [Google Scholar] [CrossRef]
  8. HONDA, A.F.K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature 1972, 238, 37–38. [Google Scholar] [CrossRef]
  9. Han, M.; Guo, B.; Zhang, Z.; Hu, X.; Wang, Z. Hollow Bi4Ti3O12/TiO2 nanocakes for photocatalytic hydrogen generation. J. Alloys Compd. 2023, 963, 171192. [Google Scholar] [CrossRef]
  10. Ren, T.; Dang, Y.; Xiao, Y.; Hu, Q.; Deng, D.; Chen, J.; He, P. Depositing Ag nanoparticles on g-C3N4 by facile silver mirror reaction for enhanced photocatalytic hydrogen production. Inorg. Chem. Commun. 2021, 123, 108367. [Google Scholar] [CrossRef]
  11. Xiao, Y.; Liu, J.; Leng, J.; Yin, Z.; Yin, Y.; Zhang, F.; Sun, C.; Jin, S. Long-Lived Internal Charge-Separated State in Two-Dimensional Metal–Organic Frameworks Improving Photocatalytic Performance. ACS Energy Lett. 2022, 7, 2323–2330. [Google Scholar] [CrossRef]
  12. Zhang, Y.; Liu, D.; Shi, J.; Chen, P.; Zong, S.; Cheng, C.; Chen, K.; Chen, Y.; Ma, L. (Oxy)nitride heterojunction-strengthened separation of photogenerated carriers in g-C3N4 towards enhanced photocatalytic H2 evolution. Appl. Catal. A Gen. 2022, 643, 118746. [Google Scholar] [CrossRef]
  13. Yang, H.; Li, C.; Mao, M.; Sun, H.; Zhu, X.; Zhang, Y.; Li, Y.; Jiang, Z. Synthesis of Type-S Ni3S4/ZnCdS Quantum Dots via Constitution Controller l-Cysteine for Photocatalytic H2 Evolution. ACS Appl. Nano Mater. 2024, 7, 22093–22103. [Google Scholar] [CrossRef]
  14. Du, S.; Chen, L.; Men, C.; Ji, H.; Su, T.; Qin, Z. Effect of surface defect states on Zn(1−x)CdxS for enhanced photocatalytic hydrogen evolution. J. Alloys Compd. 2023, 955, 170265. [Google Scholar] [CrossRef]
  15. Zhang, L.; Jiang, T.; Li, S.; Lu, Y.; Wang, L.; Zhang, X.; Wang, D.; Xie, T. Enhancement of photocatalytic H2 evolution on Zn0.8Cd0.2S loaded with CuS as cocatalyst and its photogenerated charge transfer properties. Dalton Trans. 2013, 42, 12998. [Google Scholar] [CrossRef]
  16. Li, S.; Li, Y.; Yin, W.; Su, K.; He, P.; Chen, J.; Si, Y.; Xiao, Y.; Ren, T. Boosting the photocatalytic hydrogen production activity of marigold-like Zn2In2S5 by using noble-metal-free Ni2P as cocatalyst. Int. J. Hydrogen Energy 2024, 56, 596–603. [Google Scholar] [CrossRef]
  17. Li, Y.; Jin, Z.; Tsubaki, N. Hollow ZnCdS and NiCoP Nanostructures for Photocatalytic Hydrogen Generation. ACS Appl. Nano Mater. 2022, 5, 14677–14688. [Google Scholar] [CrossRef]
  18. Li, M.; Chen, F.; Xu, Y.; Tian, M. Ni(OH)2 Nanosheet as an Efficient Cocatalyst for Improved Photocatalytic Hydrogen Evolution over Cd0.9Zn0.1S Nanorods under Visible Light. Langmuir 2024, 40, 3793–3803. [Google Scholar] [CrossRef]
  19. Kong, Z.; Kong, Z.; Zhang, D.; Liu, J.; Ji, X.-Y.; Cai, P.; Pu, X. Magnetic separable non-precious metal Schottky heterojunction photocatalyst toward photothermal-assisted photocatalytic hydrogen evolution. Sep. Purif. Technol. 2025, 361, 131429. [Google Scholar] [CrossRef]
  20. Zhang, Q.; Wang, Z.; Song, Y.; Fan, J.; Sun, T.; Liu, E. S-scheme regulated Ni2P-NiS/twinned Mn0.5Cd0.5S hetero-homojunctions for efficient photocatalytic H2 evolution. J. Mater. Sci. Technol. 2024, 169, 148–157. [Google Scholar] [CrossRef]
  21. Ma, F.; Wen, Y.; Fu, P.; Zhang, J.; Tang, Q.; Chen, T.; Luo, W.; Zhou, Y.; Wang, J. Engineering 0D/2D Architecture of Ni(OH)2 Nanoparticles on Covalent Organic Framework Nanosheets for Selective Visible-Light-Driven CO2 Reduction. Small 2023, 20, 2305767. [Google Scholar] [CrossRef]
  22. Zuo, L.; Yang, N.; Xia, W.; Zeng, X.; Cao, R. Z-scheme NiS@ZnCdS heterostructures and their boosted photocatalytic H2 evolution. Appl. Surf. Sci. 2025, 689, 162447. [Google Scholar] [CrossRef]
  23. Lu, L.; Ma, Y.; Liu, H.; Dong, R.; Tan, P.; Yang, L.; Pan, J. Controlled preparation of hollow Zn0.3Cd0.7S nanospheres modified by NiS1.97 nanosheets for superior photocatalytic hydrogen production. J. Colloid Interface Sci. 2022, 606, 1–9. [Google Scholar] [CrossRef] [PubMed]
  24. Zhu, X.; Wang, Z.; Zhong, K.; Li, Q.; Ding, P.; Feng, Z.; Yang, J.; Du, Y.; Song, Y.; Hua, Y.; et al. Mo-O-Bi Bonds as interfacial electron transport bridges to fuel CO2 photoreduction via in-situ reconstruction of black Bi2MoO6/BiO2-x heterojunction. Chem. Eng. J. 2022, 429, 132204. [Google Scholar] [CrossRef]
  25. Gao, L.; Chen, Z.; Zheng, H.; Hu, J. A distinct hollow spindle-like CdIn2S4 photocatalyst for high-efficiency tetracycline removal. Mater. Today Chem. 2022, 24, 100800. [Google Scholar] [CrossRef]
  26. Moridon, S.N.F.; Arifin, K.; Mohamed, M.A.; Minggu, L.J.; Mohamad Yunus, R.; Kassim, M.B. Improving photoelectrochemical performance of transferred TiO2 nanotubes onto FTO substrate with Mo2C and NiS as Co-catalyst. Int. J. Hydrogen Energy 2024, 88, 1196–1206. [Google Scholar] [CrossRef]
  27. Bai, X.; Yang, T.; Zhao, M.; Fan, H.; Li, C.; Liu, E. Novel N-deficient g-C3N4 /Ni(OH)2 2D heterojunction design for efficient photocatalytic H2 evolution. J. Environ. Chem. Eng. 2025, 13, 115447. [Google Scholar] [CrossRef]
  28. Zhan, D.; Tian, J.; Fu, Q.; Liu, P.; Zhao, Y.; Liu, W.; Li, D.; Huang, Y.; Han, C. In situ photodeposition of Cu and Ni(OH)2 dual cocatalyst: Synergistic effect on enhancing g-C3N4 photocatalytic H2 evolution. Appl. Surf. Sci. 2023, 641, 158463. [Google Scholar] [CrossRef]
  29. Nair, M.M.; Iacoban, A.C.; Neaţu, F.; Florea, M.; Neaţu, Ş. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis. J. Mater. Chem. A 2023, 11, 12559–12592. [Google Scholar] [CrossRef]
  30. Wang, H.; Shao, B.; Chi, Y.; Lv, S.; Wang, C.; Li, B.; Li, H.; Li, Y.; Yang, X. Engineering of Ni(OH)2 Modified Two-Dimensional ZnIn2S4 Heterostructure for Boosting Hydrogen Evolution under Visible Light Illumination. Nanomaterials 2022, 12, 946. [Google Scholar] [CrossRef] [PubMed]
  31. Wang, J.; Huang, L.; Sun, B.; Zhang, H.; Hou, D.; Qiao, X.-q.; Ma, H.; Li, D.-S. Efficient photothermal catalytic CO2 reduction over in situ construction ZnIn2S4@Ni(OH)2/NiO Z-scheme heterojunction. Chem. Eng. J. 2024, 479, 147719. [Google Scholar] [CrossRef]
  32. Chen, R.; Zhu, H.; Liu, W.; Zhan, D.; Fu, Q.; Tian, J.; Huang, Y.; Han, C. Facile photodeposition Ni(OH)2 anchored ZnIn2S4 as an efficient 1D/2D heterojunctions for photocatalytic H2 evolution. J. Am. Ceram. Soc. 2024, 107, 5201–5211. [Google Scholar] [CrossRef]
  33. Siang, T.J.; Zhang, P.; Chen, B.; Ong, W.-J. Surface defect engineering of ZnCoS in ZnCdS with twin crystal structure for visible-light-driven H2 production coupled with benzyl alcohol oxidation. Chin. J. Catal. 2025, 69, 84–98. [Google Scholar] [CrossRef]
  34. Guan, C.; Zhou, H.; Liao, Y.; Xiang, Q. 2D/2D g-C3N4/ZnxCd1-xS Van der Waals heterojunctions modulation: Interfacial chemical bond accelerating charge separation for enhanced photocatalytic CO2 reduction. Appl. Surf. Sci. 2023, 619, 156734. [Google Scholar] [CrossRef]
  35. Govindarajan, D.; Murugadoss, G.; Kirubaharan, K.; Manavalan, R.K.; Manibalan, G.; Shaikh, J.; Etesami, M.; Kheawhom, S. Improved electrochemical supercapacitive properties of CuO-Ni(OH)2 nanocomposites by eco-friendly low-temperature synthesis. J. Alloys Compd. 2023, 942, 169130. [Google Scholar] [CrossRef]
  36. Sekar, S.; Lee, S.; Kim, D.Y.; Preethi, V.; Kalirajan, K.M.; Sutha, S.; Saravanan, S.; Therli, A.; Roy, M.; Jagannathan, K. Biomass activated carbon-decorated spherical β-Ni(OH)2 nanoparticles for enhanced hydrogen production from sulphide wastewater. J. Water Process Eng. 2020, 38, 101669. [Google Scholar] [CrossRef]
  37. Li, D.; Shen, C.; Lu, Q.; Yan, R.; Xiao, B.; Zi, B.; Zhang, J.; Lu, Q.; Liu, Q. Excellent performance supercapacitors with the compounding of Ni(OH)2 and ZIF-67 derived Co–C–N nanosheets as flexible electrode materials. Nanoscale Adv. 2022, 4, 4381–4390. [Google Scholar] [CrossRef]
  38. Yang, D.; Li, Z.-G.; Lang, F.; Zhang, X.; Li, H.; Zhang, J.; Bu, X.-H. Molecular Adsorption─An Effective Modification for a ZnCdS Photocatalyst in a Hydrogen Production Reaction. ACS Mater. Lett. 2024, 6, 2837–2845. [Google Scholar] [CrossRef]
  39. Parvin, S.; Aransiola, E.; Ammar, M.; Lee, S.; Zhang, L.; Weber, J.; Baltrusaitis, J. Tailored Ni(OH)2/CuCo/Ni(OH)2 Composite Interfaces for Efficient and Durable Urea Oxidation Reaction. ACS Appl. Mater. Interfaces 2024, 16, 67715–67729. [Google Scholar] [CrossRef]
  40. Liu, X.; Zhou, Z.; Han, D.; Wang, T.; Ma, C.; Huo, P.; Yan, Y. Interface engineered 2D/2D Ni(OH)2/Bi4Ti3O12 nanocomposites with higher charge transfer towards improving photocatalytic activity. J. Alloys Compd. 2020, 816, 152530. [Google Scholar] [CrossRef]
  41. Hu, Q.; Chen, L.; Xie, X.; Qin, Z.; Ji, H.; Su, T. Construction of Electron Bridge and Activation of MoS2 Inert Basal Planes by Ni Doping for Enhancing Photocatalytic Hydrogen Evolution. Acta Phys.-Chim. Sin. 2024, 40, 2406024. [Google Scholar] [CrossRef]
  42. Liu, S.; Wang, W.; Shi, S.; Liao, S.; Zhong, M.; Xiao, W.; Wang, S.; Wang, X.; Chen, C. Hydrogen-bonded organic framework derived ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production. Appl. Surf. Sci. 2024, 657, 159795. [Google Scholar] [CrossRef]
  43. Serpone, N.; Borgarello, E.; Barbeni, M.; Pelizzetti, E. Effect of CdS Preparation on the Photo-catalyzed Decomposition of Hydrogen. Inorganica Chim. Acta 1984, 90, 191–196. [Google Scholar]
  44. Li, Z.; Liu, F.; Yan, X.; Wang, Y.; Lu, K.; Liu, J.; Qiao, Y.; Liu, M. Photoreforming lignocellulose to hydrogen over noble-metal-free Ni(OH)2/Cd0.5Zn0.5S nanotwins. Int. J. Hydrogen Energy 2024, 69, 234–241. [Google Scholar] [CrossRef]
  45. Gao, X.; Zeng, D.; Yang, J.; Ong, W.-J.; Fujita, T.; He, X.; Liu, J.; Wei, Y. Ultrathin Ni(OH)2 nanosheets decorated with Zn0.5Cd0.5S nanoparticles as 2D/0D heterojunctions for highly enhanced visible light-driven photocatalytic hydrogen evolution. Chin. J. Catal. 2021, 42, 1137–1146. [Google Scholar] [CrossRef]
  46. Xia, Y.; Chen, W.; Liang, S.; Bi, J.; Wu, L.; Wang, X. Engineering a highly dispersed co-catalyst on a few-layered catalyst for efficient photocatalytic H2 evolution: A case study of Ni(OH)2/HNb3O8 nanocomposites. Catal. Sci. Technol. 2017, 7, 5662–5669. [Google Scholar] [CrossRef]
  47. Wang, C.; Xiong, J.; Wen, Z.; Cheng, G. Integrated Ni(OH)2-TiO2-Cu2O Hybrids with a Synergic Impact of the p–n Heterojunction/Cocatalyst for Enhanced Photocatalytic Hydrogen Production. Ind. Eng. Chem. Res. 2023, 62, 11402–11413. [Google Scholar] [CrossRef]
  48. Liu, H.; Su, P.; Jin, Z.; Ma, Q. Enhanced Hydrogen Evolution over Sea-Urchin-Structure NiCoP Decorated ZnCdS Photocatalyst. Catal. Lett. 2020, 150, 2937–2950. [Google Scholar] [CrossRef]
  49. Li, Q.; Jin, F.; Liu, J.; Wang, P.; Yang, B.; Jin, Z. Construction of S-scheme CoMn2O4/ZnCdS p–n heterojunction for enhanced photocatalytic hydrogen production. J. Mater. Chem. C 2025, 13, 7380–7392. [Google Scholar] [CrossRef]
  50. Chen, C.; Xia, Q.; Li, Z.; Wang, Y. Microwave synthesis and photocatalytic H2 production performance of SiO2 aerogel/ZnCdS solid solution catalyst. Inorg. Chem. Commun. 2024, 168, 112874. [Google Scholar] [CrossRef]
  51. Zou, Y.; Guo, C.; Cao, X.; Chen, T.; Kou, Y.; Zhang, L.; Wang, T.; Akram, N.; Wang, J. Photocatalytic performance and mechanism of hydrogen evolution from water over ZnCdS/Co@CoO in sacrificial agent-free system. Int. J. Hydrogen Energy 2022, 47, 25289–25299. [Google Scholar] [CrossRef]
  52. Li, L.; Su, J.; Qiu, Y.; Gao, Y.; Li, N.; Ge, L. Design and fabrication of ternary Au/Co3O4/ZnCdS spherical composite photocatalyst for facilitating efficient photocatalytic hydrogen production. Chin. J. Struct. Chem. 2024, 43, 100472. [Google Scholar] [CrossRef]
  53. Bai, T.; Shi, X.; Liu, M.; Huang, H.; Zhang, J.; Bu, X.-H. g-C3N4/ZnCdS heterojunction for efficient visible light-driven photocatalytic hydrogen production. RSC Adv. 2021, 11, 38120–38125. [Google Scholar] [CrossRef] [PubMed]
  54. Xiao, Q.; Yang, T.; Guo, X.; Jin, Z. S-scheme heterojunction constructed by ZnCdS and CoWO4 nano-ions promotes photocatalytic hydrogen production. Surf. Interfaces 2023, 43, 103577. [Google Scholar] [CrossRef]
Catalysts 15 00886 g001
Figure 1. XRD patterns (a) and FT-IR spectra (b) of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites. (The figure on the right side of (a) shows the enlarged patterns of the dash box in (a)).
Figure 1. XRD patterns (a) and FT-IR spectra (b) of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites. (The figure on the right side of (a) shows the enlarged patterns of the dash box in (a)).
Catalysts 15 00886 g001
Catalysts 15 00886 g002
Figure 2. SEM images of Zn0.8Cd0.2S (a), Ni(OH)2 (b), 1Ni(OH)2/ZCS (c), 5Ni(OH)2/ZCS (d), 9Ni(OH)2/ZCS (e), and 13Ni(OH)2/ZCS (f).
Figure 2. SEM images of Zn0.8Cd0.2S (a), Ni(OH)2 (b), 1Ni(OH)2/ZCS (c), 5Ni(OH)2/ZCS (d), 9Ni(OH)2/ZCS (e), and 13Ni(OH)2/ZCS (f).
Catalysts 15 00886 g002
Catalysts 15 00886 g003
Figure 3. TEM images, HRTEM images, and SAED patterns of Zn0.8Cd0.2S (a–c) and Ni(OH)2 (d–f).
Figure 3. TEM images, HRTEM images, and SAED patterns of Zn0.8Cd0.2S (a–c) and Ni(OH)2 (d–f).
Catalysts 15 00886 g003
Catalysts 15 00886 g004
Figure 4. TEM images (a), HRTEM images (b), SAED patterns (c), HAADF-STEM images and corresponding elemental (Zn, Cd, S, Ni, O) mappings (d) of 9Ni(OH)2/ZCS.
Figure 4. TEM images (a), HRTEM images (b), SAED patterns (c), HAADF-STEM images and corresponding elemental (Zn, Cd, S, Ni, O) mappings (d) of 9Ni(OH)2/ZCS.
Catalysts 15 00886 g004
Catalysts 15 00886 g005
Figure 5. XPS survey spectra (a) and high-resolution XPS spectra of Cd 3d (b), Zn 2p (c), S 2p (d), Ni 2p (e), and O 1s (f) in Zn0.8Cd0.2S, Ni(OH)2, and 9Ni(OH)2/ZCS.
Figure 5. XPS survey spectra (a) and high-resolution XPS spectra of Cd 3d (b), Zn 2p (c), S 2p (d), Ni 2p (e), and O 1s (f) in Zn0.8Cd0.2S, Ni(OH)2, and 9Ni(OH)2/ZCS.
Catalysts 15 00886 g005
Catalysts 15 00886 g006
Figure 6. UV–vis diffuse reflectance spectra of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites (a), band gap (b) of Zn0.8Cd0.2S.
Figure 6. UV–vis diffuse reflectance spectra of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites (a), band gap (b) of Zn0.8Cd0.2S.
Catalysts 15 00886 g006
Catalysts 15 00886 g007
Figure 7. PL spectra (a), TRPL spectra (b), transient photocurrent response (c), and EIS Nyquist plots of Zn0.8Cd0.2S and 9Ni(OH)2/ZCS (d).
Figure 7. PL spectra (a), TRPL spectra (b), transient photocurrent response (c), and EIS Nyquist plots of Zn0.8Cd0.2S and 9Ni(OH)2/ZCS (d).
Catalysts 15 00886 g007
Catalysts 15 00886 g008
Figure 8. Photocatalytic H2 production performance of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites (a) and the AQY of 9Ni(OH)2/ZCS at different wavelengths of 380, 400, 420, and 450 nm (b).
Figure 8. Photocatalytic H2 production performance of the Zn0.8Cd0.2S, Ni(OH)2, and Ni(OH)2/ZCS composites (a) and the AQY of 9Ni(OH)2/ZCS at different wavelengths of 380, 400, 420, and 450 nm (b).
Catalysts 15 00886 g008
Catalysts 15 00886 g009
Figure 9. UPS spectrum (a) and energy level structures of Zn0.8Cd0.2S (b).
Figure 9. UPS spectrum (a) and energy level structures of Zn0.8Cd0.2S (b).
Catalysts 15 00886 g009
Catalysts 15 00886 g010
Figure 10. Charge transfer pathway and mechanism of photocatalytic hydrogen production over Ni(OH)2/ZCS composites under visible light irradiation.
Figure 10. Charge transfer pathway and mechanism of photocatalytic hydrogen production over Ni(OH)2/ZCS composites under visible light irradiation.
Catalysts 15 00886 g010
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Feng, Q.; Yu, X.; Peng, J.; Du, S.; Chen, L.; Xu, X.; Su, T. Zn0.8Cd0.2S Photocatalyst Modified with Ni(OH)2 for Enhanced Photocatalytic Hydrogen Production. Catalysts 2025, 15, 886. https://doi.org/10.3390/catal15090886

AMA Style

Feng Q, Yu X, Peng J, Du S, Chen L, Xu X, Su T. Zn0.8Cd0.2S Photocatalyst Modified with Ni(OH)2 for Enhanced Photocatalytic Hydrogen Production. Catalysts. 2025; 15(9):886. https://doi.org/10.3390/catal15090886

Chicago/Turabian Style

Feng, Qianran, Xiaoting Yu, Jinlian Peng, Siying Du, Liuyun Chen, Xinyuan Xu, and Tongming Su. 2025. "Zn0.8Cd0.2S Photocatalyst Modified with Ni(OH)2 for Enhanced Photocatalytic Hydrogen Production" Catalysts 15, no. 9: 886. https://doi.org/10.3390/catal15090886

APA Style

Feng, Q., Yu, X., Peng, J., Du, S., Chen, L., Xu, X., & Su, T. (2025). Zn0.8Cd0.2S Photocatalyst Modified with Ni(OH)2 for Enhanced Photocatalytic Hydrogen Production. Catalysts, 15(9), 886. https://doi.org/10.3390/catal15090886

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop