Search Results (153)

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. Graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu₂O derived from urea pyrolysis (Cu₂O-u) was prepared by thermal reduction of urea and CuCl₂·2H₂O at 180 °C. The heterojunction Cu₂O-u/g-C₃N₄ was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO₂ photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C₃N₄ by 3.14-fold and TiO₂ by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h⁻¹·g_cat⁻¹. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h⁻¹·g_cat⁻¹, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO₂ photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research. Full article

Aiming to contribute to environmental remediation strategies, this work proposes a novel fabrication of photoelectrocatalytic electrodes containing a BiOI coating deposited onto non-conductive glass (NCG) for CO₂ conversion applications. When BiOI electrodes are not deposited onto fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) conductive supports, the electrochemical measurements enable the registration of the (photo)electrochemical response for bare BiOI, thereby excluding remnant signals from the conductive supports and reporting an exclusive and proper photoelectrocatalytic BiOI response. A systematic procedure was carried out to improve the physicochemical properties of BiOI through a simple variation in the amount of reagents employed in a solvothermal synthesis, thus increasing the crystallite size and surface area of the resulting material (BiOI-X3-20wt.%). The tailored BiOI coating on a non-conductive support showed activity in performing CO₂ photoelectroreduction under UV–Vis irradiation in aqueous media. Finally, the BiOI-X3-20wt.% sample was evaluated for photocatalytic CO₂ conversion in gaseous media, producing CO as the primary reaction product. This study confirms that BiOI is a suitable and easily synthesized material, with potential applications for CO₂ capture and conversion when employed as a photoactive coating for environmental remediation. Full article

The conversion of CO₂ into CH₄ through the Sabatier reaction is one of the key processes that can reduce CO₂ emissions into the atmosphere. This work aims to develop Ni-Al aerogel-based thermo-photocatalysts with large specific surface areas prepared using a sol–gel method and subsequent supercritical drying in CO₂. Different Al/Ni molar ratios were selected for the development of the catalysts, characterized using ICP-OES, N₂ adsorption–desorption isotherms, XRD, H₂-TPR, TEM, UV-Vis DRS, and XPS techniques. Thermo-photocatalytic activity tests were performed in a photoreactor with two different light sources (λ = 365 nm, λ = 470 nm) at a temperature range from 300 °C to 450 °C and a pressure of 10 bar. The catalyst with the highest Ni loading (AG 1/3) produced the best catalytic results, reaching CO₂ conversion and CH₄ selectivity levels of 82% and 100%, respectively, under visible light at 450 °C. In contrast, the catalysts with the lowest nickel loading produced the lowest results, most likely due to their low amounts of active Ni. These results suggest that supercritical drying is an efficient method for developing active thermo-photocatalysts with high Ni dispersion, suitable for Sabatier reactions under mild reaction conditions. Full article

Visible-light-driven photocatalytic hydrogen production is one of the ideal green technologies for solar-to-chemical energy conversion. Carbon nitride (C₃N₄, CN) has been attracting extensive attention for its suitable band structure and stability, but the efficiency of photocatalytic hydrogen evolution is low due to insufficient visible-light absorption and rapid charge recombination. Herein, we develop a novel (F, K)-co-doped CN (FKCN) catalyst via a facile thermal polymerization approach using KOH-modified melamine and NH₄F as the dopant precursors. The FKCN catalyst demonstrates broadened light absorption, significantly enhanced charge separation, and excellent cyclic stability. And the optimal F_(0.15)K₍₆₎CN catalyst achieves a hydrogen evolution rate of as high as 3101.5 μmol g⁻¹ h⁻¹ (12-fold that of pristine CN) under visible-light irradiation (λ ≥ 420 nm), which is among the best element-doped CN photocatalysts. This work highlights the effectiveness of a multi-element doping strategy in designing CN-based photocatalysts for efficient hydrogen evolution. Full article

The photocatalytic reduction of CO₂ into valuable hydrocarbons presents significant potential. In this research, a ZnO/ZnAl₂O₄ composite photocatalyst was synthesized using the hydrothermal method, resulting in a marked enhancement in CO yield—approximately three times greater than that achieved with pure ZnAl₂O₄ nanoparticles. The formation of a Z-scheme heterojunction between ZnO and ZnAl₂O₄ was observed, characterized by low interfacial charge transfer resistance, an abundance of reaction sites, and optimized charge transport pathways. Within this composite, ZnO contributes additional vacancies, thereby increasing active sites and enhancing the separation and migration of photogenerated carriers. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis indicates that ZnAl₂O₄ facilitates the formation of key intermediates, such as *COOH and HCO₃⁻, thus promoting the conversion of CO₂ to CO. This study offers valuable insights into the design of heterogeneous catalysts with diverse active components to enhance the performance of CO₂ photocatalytic reduction through synergistic effects. Full article

Photocatalytic CO₂ conversion is one of the ideal approaches to address both topics of solar energy shortage and carbon neutrality. Cobalt(II) centers coordinated with bipyridines have been designed and evaluated as catalysts for CO₂ conversion under light irradiation. Herein, we report a series of pyridine-based cobalt complexes with alkyl substituents as molecular photocatalysts, aiming to elucidate the effects of alkyl type and substitution position on catalytic performance through spectroscopic and electrochemical measurements. The substitution of the hydrogen at 4,4′-positions on the bipyridine ring with a methyl group, a tert-butyl group, and a nonyl group led to a decrease in the conversion rate of CO₂ by 13.2%, 29.6%, and 98%, respectively. The methyl substituents at the 5, 5′-positions of the bipyridine ring resulted in a 71.1% decrease in the CO₂ conversion rate. The usage of either 6, 6′-Me₂-2,2′-bipy, 2,4-bipy, or 3,3′-bipy resulted in no detectable activity for CO₂ conversion in the current system. Both photo- and electrochemical analyses have been employed to reveal the relationship between changing ligands and photocatalytic performance on the molecular scale. These results demonstrate that bulky ligands significantly hinder CO₂ reduction by cobalt complexes due to steric interference with coordination and active-site accessibility. This study demonstrates that the substituent effect of ligands on photocatalytic reactions for CO₂ conversion provides valuable insight into a deeper understanding of molecular catalysis. Full article

Owing to global energy demands and climate change resulting from fossil fuel use, technologies capable of converting greenhouse gases into renewable energy resources are needed. One such technology is photocatalytic CO₂ reduction, which utilises solar energy to transform CO₂ into value-added hydrocarbons. However, the application of photocatalytic CO₂ reduction is limited by the inefficiency of existing photocatalysts. In this study, we developed a nitrogen-deficient g-C₃N₄-confined PtCu dual-atom catalyst (PtCu/V_N-C₃N₄) for photocatalytic CO₂ reduction. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomic-level anchoring of PtCu pairs onto the nitrogen-vacancy-rich g-C₃N₄ nanosheets. The optimised PtCu/V_N-C₃N₄ exhibited superior photocatalytic performance, with CO and CH₄ evolution rates of 13.3 µmol/g/h and 2.5 µmol/g/h, respectively, under visible-light irradiation. Mechanistic investigations revealed that CO₂ molecules were preferentially adsorbed onto the PtCu dual sites, initiating a stepwise reduction pathway. In situ diffuse reflectance infrared Fourier-transform spectroscopy identified the formation of a key intermediate (HCOO*), whereas interfacial wettability studies demonstrated efficient H₂O adsorption on PtCu sites, providing essential proton sources for CO₂ protonation. Photoelectrochemical characterisation further confirmed the enhanced charge-transfer kinetics in PtCu/V_N-C₃N₄, which were attributed to the synergistic interplay between the nitrogen vacancies and dual-atom sites. Notably, the dual-active-site architecture minimised the competitive adsorption between CO₂ and H₂O molecules, thereby optimising the surface reaction pathways. This study establishes a rational strategy for designing atomically precise dual-atom catalysts through defect engineering, achieving concurrent improvements in activity, selectivity, and charge carrier utilisation for solar-driven CO₂ conversion. Full article

The widespread presence of pesticides—especially malathion—in aquatic environments presents a major obstacle to conventional remediation strategies, while the ongoing global energy crisis underscores the urgency of developing renewable energy sources such as hydrogen. In this context, photocatalytic water splitting emerges as a promising approach, though its practical application remains limited by poor charge carrier dynamics and insufficient visible-light utilization. Herein, we report the design and evaluation of a series of TiO₂-based ternary nanocomposites comprising commercial P25 TiO₂, reduced graphene oxide (rGO), and molybdenum disulfide (MoS₂), with MoS₂ loadings ranging from 1% to 10% by weight. The photocatalysts were fabricated via a two-step method: hydrothermal integration of rGO into P25 followed by solution-phase self-assembly of exfoliated MoS₂ nanosheets. The composites were systematically characterized using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity was assessed through two key applications: the degradation of malathion (20 mg/L) under simulated solar irradiation and hydrogen evolution from water in the presence of sacrificial agents. Quantification was performed using UV-Vis spectroscopy, gas chromatography–mass spectrometry (GC-MS), and thermal conductivity detection (GC-TCD). Results showed that the integration of rGO significantly enhanced surface area and charge mobility, while MoS₂ served as an effective co-catalyst, promoting interfacial charge separation and acting as an active site for hydrogen evolution. Nearly complete malathion degradation (~100%) was achieved within two hours, and hydrogen production reached up to 6000 µmol g⁻¹ h⁻¹ under optimal MoS₂ loading. Notably, photocatalytic performance declined with higher MoS₂ content due to recombination effects. Overall, this work demonstrates the synergistic enhancement provided by rGO and MoS₂ in a stable P25-based system and underscores the viability of such ternary nanocomposites for addressing both environmental remediation and sustainable energy conversion challenges. Full article

The urgent need for sustainable CO₂ conversion technologies has driven the development of advanced photocatalysts that harness solar energy. This study employs a CTAB-assisted solvothermal method to fabricate a Z-scheme heterojunction Fe-MOFs/V_O-Bi₂WO₆ (FM/V_O-BWO) for photocatalytic CO₂ reduction. Positron annihilation lifetime spectroscopy (PALS) was employed to confirm the existence of oxygen vacancies, while spherical aberration-corrected transmission electron microscope (STEM) characterization verified the successful construction of heterointerfaces. X-ray absorption fine structure (XAFS) spectra confirmed that the defect configuration and heterostructure changed the surface chemical valence state. The optimized 1.0FM/V_O-BWO composite demonstrated exceptional photocatalytic performance, achieving CO and CH₄ yields of 60.48 and 4.3 μmol/g, respectively, under visible-light 11.8- and 1.5-fold enhancements over pristine Bi₂WO₆. The enhanced performance is attributed to oxygen vacancy-induced active sites facilitating CO₂ adsorption/activation. In situ molecular spectroscopy confirmed the formation of critical CO₂-derived intermediates (COOH* and CHO*) through surface interactions involving four-coordinated and two-coordinated hydrogen-bonded water molecules. Furthermore, the accelerated interfacial charge transfer efficiency mediated by the Z-scheme heterojunction has been conclusively demonstrated. This work establishes a paradigm for defect-mediated heterojunction design, offering a sustainable route for solar fuel production. Full article

Converting carbon dioxide (CO₂) into high-value fuels through the photothermal effect offers an effective approach to enhancing the carbon cycle and reducing the greenhouse effect. In this study, we developed Ag/C-TCN-x, a carbon nitride-based photocatalyst that integrates both photothermal and localized surface plasmon resonance (LSPR) effects. This material was synthesized through a three-step process involving hydrothermal treatment, calcination, and photo-deposition. Real-time infrared thermography monitoring revealed that Ag/C-TCN-2 reached a surface stabilization temperature of approximately 176 °C, which was 1.5 times higher than C-TCN and 2.2 times higher than g-C₃N₄. Under the same experimental conditions, Ag/C-TCN demonstrated a carbon monoxide (CO) release rate 3.3 times greater than that of pure g-C₃N₄. The composite sample Ag/C-TCN-2 maintained good photocatalytic activity in five cycling tests. The structural stability of the sample after the cycling tests was confirmed by X-ray diffraction (XRD) test. The unique tubular structure of Ag/C-TCN increased its specific surface area, facilitating enhanced CO₂ adsorption. Carbon doping not only triggered the photothermal effect but also accelerated the conversion of carriers. Additionally, the LSPR effect of Ag nanoparticles, combined with carbon doping, optimized charge carrier dynamics and promoted efficient CO₂ photoreduction. The CO₂ reduction mechanism over Ag/C-TCN was further examined using in situ Fourier Transform Infrared (FT-IR) spectroscopy. This research offers valuable insights into how photothermal and LSPR effects can be harnessed to enhance the efficiency of CO₂ photoreduction. Full article

The use of solar energy to convert CO₂ into value-added chemicals is a promising sustainable development strategy. In this study, a black graphitic carbon nitride (CN-B) photocatalyst was fabricated through a single-step calcination process, employing phloxine B and urea as the precursor materials. The catalysts were characterized using TEM, XRD, FTIR, XPS and so on. The amount of prepolymer phloxine B was 25 mg, 35 mg and 45 mg, respectively, and the obtained samples were CN-B-0.025, CN-B-0.035 and CN-B-0.045. All samples were used for visible-catalyzed CO₂ reduction. The experimental findings indicate that the CO evolution rate of the optimal photocatalyst CN-B-0.035 reaches 27.56 μmol g_cat.⁻¹ h⁻¹. This value is nine-fold higher than that of pure CN, which has a CO evolution rate of 3.22 μmol g_cat.⁻¹ h⁻¹. The excellent photocatalytic reduction performance is due to the following factors: Firstly, the exceedingly thin nanosheet structure of the catalyst enhances the velocity of the charge transfer, and transmission electron microscopy (TEM) analysis shows that the nanosheet thickness of the catalyst CN-B is significantly thinner. Secondly, the light absorption capacity of the catalyst is enhanced. The absorbance of CN-B increases significantly in the ultraviolet region and extends to the near-infrared region, as shown with UV diffuse reflection spectroscopy. Finally, the photothermal effect of CN-B causes the catalyst temperature to rise rapidly from 20 °C to 131 °C within 120 s, which further promotes photogenerated carrier separation. This research offers a novel approach to the development of photocatalysts aimed at the photothermal-assisted photocatalytic conversion of CO₂. Full article

In recent years, metal–organic frameworks (MOFs) have garnered significant attention as highly efficient catalysts for CO₂ photoreduction, owing to their unique electronic configurations and exceptional CO₂ adsorption properties. This review provides a comprehensive analysis of recent advancements in the design, synthesis, and application of MOF-based photocatalysts for CO₂ reduction. Following a concise overview of the fundamental properties of MOF materials, the review focuses on pure MOFs, highlighting the structural and functional roles of metal clusters and organic ligands. Subsequently, it explores into MOF-based composites, analyzing their compositional design, CO₂ uptake capabilities, and photocatalytic efficiency. This review concludes by discussing the current challenges, future opportunities, and potential research directions for MOF photocatalysts in the field of CO₂ conversion, offering valuable insights to advance this rapidly progressing field. Full article

As global CO₂ emissions continue to rise, addressing their environmental impact is critical in combating climate change. Photocatalytic CO₂ reduction, which mimics natural photosynthesis by converting CO₂ into valuable fuels and chemicals using solar energy, represents a promising approach for both reducing emissions and storing energy sustainably. However, the development of efficient photocatalysts, particularly those capable of absorbing visible light, remains a challenge. Graphitic carbon nitride (g-C₃N₄) has gained attention for its visible light absorption and chemical stability, though its performance is hindered by rapid electron–hole recombination. Similarly, bismuth tungstate (Bi₂WO₆) is a visible-light-active photocatalyst with promising properties, but also suffers from limited efficiency due to charge recombination. To overcome these limitations, this study focuses on the design and synthesis of a g-C₃N₄/Bi₂WO₆ composite photocatalyst, leveraging the complementary properties of both materials. The composite benefits from enhanced charge separation through the formation of a heterojunction, reducing recombination rates and improving overall photocatalytic performance. The optimized g-C₃N₄/Bi₂WO₆ composite exhibited significant improvements in the production rates of both CH4 and CO, achieving 18.90 and 17.78 μmol/g/h, respectively, which are 2.6 times and 1.6 times higher than those of pure B_i2WO₆. The study explores how optimizing the g-C₃N₄/Bi₂WO₆ interface, increasing surface area, and adjusting material ratios can further enhance the efficiency of CO₂ reduction. Our findings demonstrate the potential of this composite for solar-driven CO₂ conversion, offering new insights into photocatalyst design and paving the way for future advancements in CO₂ mitigation technologies. Full article

The photocatalytic reduction of CO₂ to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO₂ reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu²⁺ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO₂ to CH₄ and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO₂ conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample. Full article

Photocatalysis offers a powerful approach for water purification from toxic organics, hydrogen production, biosolids processing, and the conversion of CO₂ into useful products. Further advancements in photocatalytic technologies depend on the development of novel, highly efficient catalysts and optimized synthesis methods. This study aimed to develop a laser synthesis technique for bismuth oxyhalide nanoparticles (NPs) as efficient and multifunctional photocatalysts. Laser ablation of a Bi target in a solution containing halogen salt precursors, followed by laser plasma treatment of the resulting colloid, yielded crystalline bismuth oxyhalides (Bi_xO_yX_z, where X = Cl, Br, or I) NPs without the need for additional annealing. The composition, structure, morphology, and optical properties of the synthesized Bi_xO_yX_z (X = Cl, Br, I) NPs were characterized using XRD analysis, electron microscopy, Raman spectroscopy, and UV-Vis spectroscopy. The effect of the halogen on the photocatalytic activity of the double oxides was investigated. The materials exhibited high photocatalytic activity in the degradation of persistent model pollutants like Rhodamine B, tetracycline, and phenol. Furthermore, the Bi_xO_yX_z NPs demonstrated good efficiency and high yield in the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). The obtained results highlight the promising potential of this laser synthesis approach for producing high-performance bismuth oxyhalide photocatalysts. Full article