Search Results (21)

The insufficient durability of electrocatalysts constitutes a critical bottleneck for electrocatalytic nitrate-to-ammonium reduction (NRA), and most existing stabilization strategies are implemented under harsh modification conditions. Herein, a sequential polymerization substitution polymerization strategy is proposed to fabricate a porous NDI-PPy conductive hydrogel catalytic electrode on a self-supported Ag-FeOOH substrate. Initially, an ND hydrogel network is constructed through the copolymerization of N-acryloxysuccinimide (NAS) and N,N-dimethylacrylamide (DMA). Amine-rich aromatic units were subsequently introduced through mild substitution with 4,4′-iminodianiline (IDA) to form the NDI hydrogel, and conductive polypyrrole (PPy) is further grown via Fe³⁺-triggered in situ polymerization of pyrrole. This non-invasive strategy is designed to preserve the catalytic functionality of the Ag-FeOOH substrate, while the comparative electrochemical results suggest improved cycling durability and enhanced apparent electrode-level performance after hydrogel modification. The optimized NDI-PPy/Ag-FeOOH electrode exhibits excellent initial NRA performance, including 89.34% NO₃⁻-N removal efficiency, 94.27% NH₄⁺-N selectivity, 89.53% Faradaic efficiency, and an NH₄⁺-N yield rate of 2.95 mg h⁻¹ cm⁻². Systematic comparative tests are conducted on identical substrates modified with conventional PAM, SA, PVA, and PAA hydrogels, as well as NDI- and PPy-containing hydrogel systems. The comparative results suggest that amine functionalization may contribute to improved electrode stability, while the incorporation of PPy is associated with enhanced ammonium production under the tested conditions. This study provides a novel and non-invasive hydrogel-modified paradigm for the durability optimization of electrocatalytic NRA catalysts. Full article

In nitrate electrochemical reduction reaction (NO₃RR), competing side reactions like hydrogen evolution often lead to poor selectivity and subpar kinetics, limiting practical use. Herein, using iron oxyhydroxide nanoarrays grown on a titanium mesh as the substrate, silver nanoparticles were introduced onto the tips of the iron oxyhydroxide nanowires via electrochemical deposition, thereby forming an Ag/FeOOH heterojunction electrocatalyst. At −0.85 V, Ag/FeOOH demonstrates excellent performance, with 97.56% ammonium selectivity, 92.45% nitrate conversion rate, and an ammonium yield of 3.21 mg h⁻¹ cm⁻². Furthermore, the Zn-NO₃⁻ battery exhibited a power density of 1.28 mW cm⁻². Ag/FeOOH’s structure enhances interfacial nitrate adsorption and reduces NO₃RR energy barriers, accelerating reaction kinetics. It promotes NO₃⁻-to-NO₂⁻ conversion via dual-site synergy, boosting NH₄⁺ yield and advancing electrocatalyst design. Full article

The highly efficient performance of photoelectrochemical (PEC) water splitting is largely governed by the construction of active interfaces, especially for the star semiconductor/electrocatalyst system. However, traditional strategies struggle to optimize this critical process. To overcome this challenge, we report a fluorine (F) engineering strategy that enables the synchronous modulation of charge transfer and surface catalytic reaction dynamics in a BiVO₄/FeCoOOH-integrated photoanode. Various characterization methods confirm that F engineering can activate the BiVO₄/FeCoOOH/electrolyte interfaces. Benefiting from these positive effects, the optimized BiVO₄/FeCoOOH-F photoanode achieves a relatively high photocurrent density of 5.46 mA/cm² at 1.23 V vs. RHE, along with outstanding photostability and a small Tafel slope of 96.5 mV dec⁻¹. This study provides new insights into F-based interface manipulation, offering a promising route to developing high-performance semiconductor/electrocatalyst systems for efficient and stable PEC water splitting applications. Full article

The development of efficient and stable oxygen evolution reaction (OER) electrocatalysts based on non-precious metals is pivotal for advancing sustainable energy conversion technologies. We present a facile and green strategy for synthesizing a high-performance HO-CDs-FeOOH/NF(D) composite catalyst by leveraging a synergistic system of FeCl₃/urea deep eutectic solvent (DES) and hydroxyl-functionalized carbon dots (HO-CDs). This system orchestrates the rapid, in situ growth of FeOOH on nickel foam (NF) via simple immersion, wherein the DES acts as both an etchant and an iron source, while the HO-CDs induce a morphological transformation from sheet-like to granular stacking, thereby constructing highly active interfaces and increasing the density of accessible catalytic sites. The optimized catalyst exhibits exceptional OER performance, requiring an overpotential of only 251 mV to achieve 50 mA cm⁻², with a Tafel slope of 55.4 mV dec⁻¹. Moreover, it demonstrates outstanding stability, maintaining 98% of its initial current density after 24 h of continuous operation and showing negligible performance decay after 3000 cycles. This work presents a straightforward approach for designing high-performance Fe-based electrocatalysts through carbon dot-mediated morphology control via a facile DES-based impregnation strategy. Full article

In this paper, we use the facile approach for preparing novel, low-cost, efficient electrocatalysts for electrocatalytic water splitting. Interfacial engineering can significantly enhance the intrinsic performance of electrocatalysts. Herein, self-supporting FeOOH/NiFe-layered double hydroxide (LDH) nanosheet arrays were synthesized via hydrothermal and impregnation methods. The resulting FeOOH/NiFe-LDH can provide more active regions, which provide more active regions for co-reaction to proceed and accelerates electron transmit processes. Additionally, the amorphous FeOOH provides abundant active sites with low coordination, leading to excellent activity. The FeOOH/NiFe-LDH demonstrates remarkable two half-reaction electrocatalytic activity, along with excellent overpotentials of 168 mV (OER) and 155 mV (HER). This research introduces a sophisticated and scalable methodology for the creation of remarkably efficient and resilient alkaline conditions specifically designed for the HER and OER. Full article

Developing high-performance oxygen evolution reaction (OER) electrocatalysts remains a critical challenge for sustainable hydrogen production via water electrolysis. Herein, we present a self-supported atomic iridium-decorated FeOOH nanostructure on iron foam (Ir-FeOOH/IF) by a facile impregnation reduction method. The self-supported Ir-FeOOH/IF electrode integrates the high electrical conductivity and outstanding mass transfer performance of IF. The FeOOH features abundant active sites, while the Ir modification regulated the electronic structure of FeOOH. As a result, the as-prepared Ir-FeOOH/IF catalyst (with the optimized synthesis time) achieves a low overpotential of 145 and 284 mV at current densities of 0.1 and 1 A cm⁻², respectively, and exhibits excellent long-term catalytic stability for 135 h at 0.1 A cm⁻² in a 1 M KOH solution. This work provides a new strategy for the design of low-cost and highly stable OER electrocatalysts. Full article

The generation of hydrogen through water electrolysis represents a significant advancement in the transition towards low-carbon energy systems. Graphene-supported catalysts have demonstrated significant potential in improving the oxygen evolution reaction (OER) among several electrocatalysts utilised for this process. Nonetheless, attaining exact control over the morphology and electrical configuration of these catalysts continues to pose a considerable difficulty. This study presents the development of a highly effective electrocatalyst composed of graphene-supported NiFe LDH and PbO₂, incorporating sulphur anions into the structure by a plasma jet treatment method. By optimising the ratio of sulphur anions, we were able to fine-tune the local coordination environment, which effectively adjusted the properties of the OH and OOH intermediates, thereby improving the OER catalytic performance. The plasma treatment introduced vacancy defects into the catalyst, further regulating its surface morphology and electronic structure. After sulphur anion optimisation, the graphene-supported catalyst exhibited excellent electrocatalytic performance in alkaline environments, achieving an OER overpotential of 228 mV at 100 mA·cm⁻². This performance, along with exceptional stability, exceeds the majority of previously documented catalysts. The results underscore the promise of sulphur anion optimisation and plasma treatment in improving OER performance, providing significant insights for the advancement of highly effective water-splitting catalysts. Full article

Currently, NiFe-LDH exhibits an excellent oxygen evolution reaction (OER) due to the interaction of the two metal elements on the layered double hydroxide (LDH) platform. However, such interaction is still insufficient to compensate for its poor electrical conductivity, limited number of active sites and sluggish dynamics. Herein, a feasible two-step hydrothermal strategy that involves coupling low-conductivity NiFe-LDH with 3D porous graphene aerogel (GA) is proposed. The optimized NiFe-LDH/GA (1:1) produced possesses a 257 mV (10 mA cm⁻²) overpotential and could operate stably for 56 h in an OER. Our investigation demonstrates that the NiFe-LDH/GA has a three-dimensional mesoporous structure, and that there is synergistic interaction between LDH and GA and interfacial reconstruction of NiOOH. Such an interface synergistic coupling effect promotes fast mass transfer and facilitates OER kinetics, and this work offers new insights into designing efficient and stable GA-based electrocatalysts. Full article

Accessible and superior electrocatalysts to overcome the sluggish oxygen evolution reaction (OER) are pivotal for sustainable and low-cost hydrogen production through electrocatalytic water splitting. The iron and nickel oxohydroxide complexes are regarded as the most promising OER electrocatalyst attributed to their inexpensive costs, easy preparation, and robust stability. In particular, the Fe-doped NiOOH is widely deemed to be superior constituents for OER in an alkaline environment. However, the facile construction of robust Fe-doped NiOOH electrocatalysts is still a great challenge. Herein, we report the facile construction of Fe-doped NiOOH on Ni(OH)₂ hierarchical nanosheet arrays grown on nickel foam (FeNi@NiA) as efficient OER electrocatalysts through a facile in-situ electrochemical activation of FeNi-based Prussian blue analogues (PBA) derived from Ni(OH)₂. The resultant FeNi@NiA heterostructure shows high intrinsic activity for OER due to the modulation of the overall electronic energy state and the electrical conductivity. Importantly, the electrochemical measurement revealed that FeNi@NiA exhibits a low overpotential of 240 mV at 10 mA/cm² with a small Tafel slope of 62 mV dec⁻¹ in 1.0 M KOH, outperforming the commercial RuO₂ electrocatalysts for OER. Full article

Introducing multiple active sites and constructing a heterostructure are efficient strategies to develop high-performance electrocatalysts. Herein, two-dimensional heterostructure NiFeP@FeOOH nanosheets supported by nickel foam (NF) are prepared by a hydrothermal–phosphorization–electrodeposition process. The synthesis of self-supporting heterostructure NiFeP@FeOOH nanosheets on NF increases the specific surface region, while bimetallic phosphide realizes rapid charge transfer, improving the electron transfer rate. The introduction of FeOOH and the construction of a heterostructure result in a synergistic effect among the components, and the surface-active sites are abundant. In situ Raman spectroscopy showed that the excellent oxygen evolution reaction (OER) performance was due to reconstruction-induced hydroxyl oxide, which achieved a multi-active site reaction. The NiFeP@FeOOH/NF electrocatalytic activity was then significantly improved. The findings indicate that in a 1.0 M KOH alkaline solution, NiFeP@FeOOH/NF showed an OER overpotential of 235 mV at 100 mA cm⁻², a Tafel slope of 46.46 mV dec⁻¹, and it worked stably at 50 mA cm⁻² for 80 h. This research proves that constructing heterostructure and introducing FeOOH are of great significance to the study of the properties of OER electrocatalysts. Full article

Oxygen evolution reactions (OER) are often the decisive step in determining the water electrolysis rate. The first row of transition metals and their derivatives, represented by Ni and Fe, have attracted much attention due to their excellent OER performance. Here, we develop a one-step strategy for preparing oxygen-evolving electrodes, in which the NiFeOOH-modified NiFe layered double hydroxide (NiFe-LDH) nanosheet is supported by nickel foam. At 100 mA·cm⁻², the overpotential of NiFeOOH-NiFe-LDH was just 227 mV, and the duration times were over 200 h in 1 mol·L⁻¹ KOH. Furthermore, the co-existence of LDH and hydroxyl oxides helps the oxygen evolution reaction. These results suggest the potential for this synthesis strategy to provide a low-cost, highly active OER electrocatalyst for industrial water splitting. Full article

The electrocatalytic oxygen evolution reaction (OER) is an arduous step in water splitting due to its slow reaction rate and large overpotential. Herein, we synthesized glycerate-anion-intercalated nickel–iron glycerates (NiFeGs) using a one-step solvothermal reaction. We designed various NiFeGs by tuning the molar ratio between Ni and Fe to obtain Ni₄Fe₁G, Ni₃Fe₁G, Ni₃Fe₂G, and Ni₁Fe₁G, which we tested for their OER performance. We initially analyzed the catalytic performance of powder samples immobilized on glassy carbon electrodes using a binder. Ni₃Fe₂G outperformed the other NiFeG compositions, including NiFe layered double hydroxide (LDH). It exhibited an overpotential of 320 mV at a current density of 10 mA cm^–2 in an electrolytic solution of pH 14. We then synthesized carbon paper (CP)-modified Ni₃Fe₂G as a self-supported electrode (Ni₃Fe₂G/CP), and it exhibited a high current density (100 mA cm⁻²) at a low overpotential of 300 mV. The redox peak analysis for the NiFeGs revealed that the initial step of the OER is the formation of γ-NiOOH, which was further confirmed by a post-Raman analysis. We extensively analyzed the catalyst’s stability and lifetime, the nature of the active sites, and the role of the Fe content to enhance the OER performance. This work may provide the motivation to study metal-alkoxide-based efficient OER electrocatalysts that can be used for alkaline water electrolyzer applications. Full article

In electrocatalytic processes, traditional powder/film electrodes inevitably suffer from damage or deactivation, reducing their catalytic performance and stability. In contrast, self-healing electrocatalysts, through special structural design or composition methods, can automatically repair at the damaged sites, restoring their electrocatalytic activity. Here, guided by Pourbaix diagrams, foam metal was activated by a simple cyclic voltammetry method to synthesize metal clusters dispersion solution (MC/KOH). The metal clusters-modified hydroxylated Ni-Fe oxyhydroxide electrode (MC/Ni_xFe_yOOH) by a facile Ni-Fe metal–organic framework-reconstructed strategy, exhibiting superior performance toward the oxygen evolution reaction (OER) in the mixture of MC/KOH and saline–alkali water (MC/KOH+SAW). Specifically, using a nickel clusters-modified hydroxylated Ni-Fe oxyhydroxide electrode (NC/Ni_xFe_yOOH) for OER, the NC/Ni_xFe_yOOH catalyst has an ultra-low overpotential of 149 mV@10 mA cm⁻², and durable stability of 100 h at 500 mA cm⁻². By coupling this OER catalyst with an efficient hydrogen evolution reaction catalyst, high activity and durability in overall SAW splitting is exhibited. What is more, benefiting from the excellent fluidity, flexibility, and enhanced catalytic activity effect of the liquid NC, we demonstrate a self-healing electrocatalysis system for OER operated in the flowing NC/(KOH+SAW). This strategy provides innovative solutions for the fields of sustainable energy and environmental protection. Full article

Metal-organic frameworks (MOFs) have been investigated with regard to the oxygen evolution reaction (OER) due to their structure diversity, high specific surface area, adjustable pore size, and abundant active sites. However, the poor conductivity of most MOFs restricts this application. Herein, through a facile one-step solvothermal method, the Ni-based pillared metal-organic framework [Ni₂(BDC)₂DABCO] (BDC = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane), its bimetallic nickel-iron form [Ni(Fe)(BDC)₂DABCO], and their modified Ketjenblack (mKB) composites were synthesized and tested toward OER in an alkaline medium (KOH 1 mol L⁻¹). A synergistic effect of the bimetallic nickel-iron MOF and the conductive mKB additive enhanced the catalytic activity of the MOF/mKB composites. All MOF/mKB composite samples (7, 14, 22, and 34 wt.% mKB) indicated much higher OER performances than the MOFs and mKB alone. The Ni-MOF/mKB14 composite (14 wt.% of mKB) demonstrated an overpotential of 294 mV at a current density of 10 mA cm⁻² and a Tafel slope of 32 mV dec⁻¹, which is comparable with commercial RuO₂, commonly used as a benchmark material for OER. The catalytic performance of Ni(Fe)MOF/mKB14 (0.57 wt.% Fe) was further improved to an overpotential of 279 mV at a current density of 10 mA cm⁻². The low Tafel slope of 25 mV dec⁻¹ as well as a low reaction resistance due to the electrochemical impedance spectroscopy (EIS) measurement confirmed the excellent OER performance of the Ni(Fe)MOF/mKB14 composite. For practical applications, the Ni(Fe)MOF/mKB14 electrocatalyst was impregnated into commercial nickel foam (NF), where overpotentials of 247 and 291 mV at current densities of 10 and 50 mA cm⁻², respectively, were realized. The activity was maintained for 30 h at the applied current density of 50 mA cm⁻². More importantly, this work adds to the fundamental understanding of the in situ transformation of Ni(Fe)DMOF into OER-active α/β-Ni(OH)₂, β/γ-NiOOH, and FeOOH with residual porosity inherited from the MOF structure, as seen by powder X-ray diffractometry and N₂ sorption analysis. Benefitting from the porosity structure of the MOF precursor, the nickel-iron catalysts outperformed the solely Ni-based catalysts due to their synergistic effects and exhibited superior catalytic activity and long-term stability in OER. In addition, by introducing mKB as a conductive carbon additive in the MOF structure, a homogeneous conductive network was constructed to improve the electronic conductivity of the MOF/mKB composites. The electrocatalytic system consisting of earth-abundant Ni and Fe metals only is attractive for the development of efficient, practical, and economical energy conversion materials for efficient OER activity. Full article

Preparing high-performance electrocatalysts for oxygen evolution reaction (OER)s with high durability for seawater electrolysis is of great significance. Herein, reported a one-step solution-immersion synthesis strategy to prepare a (Ni/Fe/Mo)OOH catalyst on a nickel foam substrate that can be accomplished in 5 min under ambient temperature and pressure. The unique cluster morphology of the catalyst on the surface of electrodes effectively increases the number of active sites, and the presence of Mo, Ni, and Fe in the catalyst enhances the activity of the OER. In the electrolyte solution (1 mol/L NaOH), the electrode exhibited low OER overpotentials of 265 mV, 286 mV, and 332 mV at currents of 100 mA·cm⁻², 400 mA·cm⁻², and 1000 mA·cm⁻², respectively. This electrode also demonstrated excellent performance in seawater splitting, and the overpotentials at currents of 100 mA·cm⁻², 400 mA·cm⁻², and 1000 mA·cm⁻² in alkaline seawater environments were 330 mV, 416 mV, and 514 mV, respectively. In the 72 h durability test, the voltage increase was within 10 mV, exhibiting the excellent durability of the (Ni/Fe/Mo)OOH electrocatalyst. Therefore, the electrode developed here shows potential in the application of seawater electrolysis for hydrogen generation. Full article