Deposition Of Cocatalysts Research Articles

Visible Light-Driven Photocatalysis of Al-Doped SrTiO3: Experimental and DFT Study

Environmental problems associated with water pollution caused by organic dyes have raised serious concerns. In this context, photocatalytic processes have proven to be promising and environmentally friendly methods for water purification utilising abundant solar energy. In this study, a SrTiO3-based photocatalyst was modified by doping with Al ions and the deposition of dual co-catalysts (Rh/Cr2O3 and CoOOH) to enhance the photocatalytic decomposition efficiency of methylene blue (MB). Pure perovskite SrTiO3 was synthesised by chemical precipitation followed by calcination at 1100 °C. Al-doped SrTiO3 with deposited co-catalysts showed 3.2 times higher photocatalytic activity compared to unalloyed SrTiO3 with co-catalysts in MB decomposition under visible radiation. This study highlights the effectiveness of using dual co-catalysts and low-valence metal doping to enhance the efficiency of the photocatalytic decomposition of organic pollutants. The density functional theory analysis results show that the Al doping of SrTiO3 improves charge separation and increases the lifetime of photogenerated electrons and holes while maintaining the size of the forbidden band, which confirms its effectiveness for enhancing photocatalytic activity.

Efficient Photocatalytic Hydrogen Evolution via Cocatalyst Loaded Al-doped SrTiO3

The growing reliance on fossil fuels is causing significant environmental issues, prompting the search for renewable energy sources. Hydrogen energy, which produces only water vapor, is a promising solution. This study focuses on developing an aluminum-doped SrTiO3 photocatalyst with dual cocatalysts (Rh/Cr2O3 and CoOOH) for efficient photocatalytic water splitting. Using a simple chemical deposition method, high-purity and crystalline SrTiO3 was synthesized and thoroughly characterized. The results show that the modified SrTiO3 achieved significantly higher photocatalytic activity, with Rh/Cr2O3/SrTiO3@Al/CoOOH producing 11.04 mmol g–1 h–1 of H2 and 4.69 mmol g–1 h–1 of O2. This work demonstrates the effectiveness of dual cocatalyst deposition and aluminum doping in enhancing photocatalytic performance by improving charge separation and reducing recombination.

Laser-Induced One-Pot Deposition of Medium-Entropy Cocatalysts on Hematite Thin Films for Improved Photoelectrochemical Water Splitting

Laser-Induced One-Pot Deposition of Medium-Entropy Cocatalysts on Hematite Thin Films for Improved Photoelectrochemical Water Splitting

A strategy to reutilize silver nanoparticles on silicon nanowires via photocathodic activation for enhanced and sustainable hydrogen evolution

The development of electrodes for hydrogen evolution via water splitting in a neutral electrolyte is highly desirable, especially considering that natural water resources such as seawater typically have a neutral pH. In this study, silicon nanowires (SiNWs) arrays with uniform silver (Ag) decoration are prepared as a cathode material, which exhibits excellent and stable electrochemical performance for neutral water electrolysis. Ag ions, utilized in the preparation of SiNWs through metal-assisted chemical etching technique, are retained and decorated within the SiNWs array without undergoing a dissolution process, referred to as Native SiNWs. Remained Ag+ ions on the SiNWs are activated photocathodically and reduced to Ag0, resulting in a significantly enhanced performance as an electrocatalyst for hydrogen evolution reaction (HER). Hence, this photocathodic activation of Native SiNWs (PCA-Native SiNWs) eliminates the need for additional cocatalyst deposition for HER, utilizing the Ag ions employed in the SiNWs preparation process. This enhancement in HER activity is exclusively observed by photocathodic activation, not by cathodic activation without light irradiation, indicating the crucial role of photoelectrons in SiNWs under light irradiation for the activation. Additionally, the nanowire structure serves as an ideal platform for Ag nanoparticles, providing sufficient surface area, resulting in excellent dispersion and an increased number of active sites. Furthermore, PCA-Native SiNWs demonstrates outstanding electrochemical stability for over 60 h, with no significant reduction in current density or structural degradation in a neutral electrolyte. Several characterizations and electrochemical analyses have been conducted to elucidate the in-situ decoration of Ag nanoparticles on SiNWs and investigate the surface chemistry for the activation mechanism. This work introduces a new perspective on using Ag-decorated SiNWs directly as an electrocatalyst for effective hydrogen evolution in a neutral media.

Oxidation of Ethylene Glycol into Valuable Chemical Using BiVO4 Photoanode

Introduction Plastic photoreforming using photocatalysts is a solar-powered technology that facilitates the generation of hydrogen (H2) from water while simultaneously breaking down plastic waste into valuable organic products. While the focus in the past few decades has predominantly centered on enhancing the H2 production efficiency, recent attention has shifted towards selective plastic oxidation reactions (U. Nwosu, et al. Renew. Sust. Energ. Rev. , 2021, 148, 111266). However, the investigation of effective cocatalysts for selective oxidation of plastic compounds has not been well studied.The photoelectrochemical (PEC) system offers a promising approach by segregating the anodic and cathodic processes, thereby enabling a more concentrated focus on the oxidation reaction in the design of reactions. In this study, we evaluate the BiVO4 photoanode modified with various cocatalysts, for example, cobalt phosphate (Co-Pi) for the oxidation of ethylene glycol (EG), a crucial component in the formation of polyethylene terephthalate (PET). Additionally, we introduce acetonitrile (MeCN) into the reactant mixture to suppress the oxygen evolution reaction (OER), which otherwise competes with the ethylene glycol oxidation reaction (EGOR), creating a more conducive reaction environment for enhanced efficiency. Materials and Methods The BiVO4 photoanode on fluorine doped tin oxide (FTO) glass was fabricated as previously reported (V. Andrei, et al. Adv. Energy Mater , 2018, 8, 1801403). Briefly,BiOI precursor was electrochemically deposited on the FTO glass and then drop-casted a vanadyl acetylacetonate [VO(acac)2] solution onto the surface and heated at 723 K for 60 min. The deposition of the Co-Pi cocatalyst onto BiVO4 was achieved by photoassisted electrodeposition method. The obtained photoanodes were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). PEC measurements were carried out using a three-electrode configuration under simulated solar irradiation (100 mW cm− 2, AM 1.5G). The experiments were performed in various solutions containing 1 M EG: 0.5 M Na2SO4 in H2O, 0.1 M NaClO4 in MeCN, and the mixed solution of MeCN and H2O. Product analysis was performed using proton nuclear magnetic resonance (1H NMR). Results and discussion According to the XRD and SEM results, the formation of nanoporous BiVO4 film on FTO glass was confirmed. To assess the PEC performance for EGOR using BiVO4 electrode, we carried out the experiments under conditions with and without the EG substrate (Figure (a)). With the addition of EG, a notable shift of the onset potential from 0.6 VRHE to 0.5 VRHE was observed. In addition, the photocurrent density at 1.2 VRHE increased from 0.67 mA/cm2 to 0.92 mA/cm2. This result indicates that EGOR is more favorable on the BiVO4 surface compared to OER. The Co-Pi cocatalyst deposition on the BiVO4 notably increased the current under both conditions, with and without the EG substrate. Although Co-Pi is commonly recognized for its catalytic role in OER, our experiment surprisingly revealed its positive impact on EG performance as well. The Co-Pi/BiVO4 photoanode exhibited a negative shift of the onset potential to 0.3 VRHE and an enhancement of photocurrent density to 2.04 mA/cm2 at 1.2 VRHE for EGOR compared to bare BiVO4. Additionally, the Co-Pi/BiVO4 photoanode showed 16.9% and 2.7% faradaic efficiencies (FE) for formate and glyoxal production, respectively, while bare BiVO4 exhibited 10.6% FE for formate and no glyoxal production.Under aqueous conditions, the FE for EGOR is currently low due to the competition between OER and EGOR. To overcome this challenge and enhance the EGOR efficiency, we introduced MeCN into the aqueous solution because MeCN has higher (more positive) anodic oxidation potential than the aqueous medium (L. M. Reid, et al. Sustainable Energy Fuels , 2018, 2, 1905-1927). In the MeCN-water mixed solution (MeCN:water = 9:1), OER was effectively suppressed to 0.33 mA/cm2, while EGOR was significantly enhanced to 2.50 mA/cm2 at 1.2 VRHE potential (Figure (b)). This MeCN-water mixed solvent created a more favorable environment for EGOR on bare BiVO4, resulting in a notable increase in FE for formate to 19.8% and FE for glyoxal to 13.2%, which represents a 1.87 and 4.89 times improvement, respectively, compared to the pure aqueous condition. Conclusions The deposition of Co-Pi cocatalyst on the BiVO4 film improved the photocurrent density and FE for formate production. Moreover, the introduction of MeCN in the solvent created a more favolable reaction condition for EGOR, suppressing OER and increasing the EGOR activity. Figure 1

(Invited) Efficient P-Doping Via Suppressing Bad P−Sn Interaction

The utilization of non-metallic phosphorus (P) doping is recognized for its advantages in enhancing the conductivity of hematite while minimizing recombination. This is attributed to the suppression of electron trapping facilitated by the favorable electron state of P5+. However, our investigation reveals a significant impact on the overall photoelectrochemical (PEC) performance of P-doped Fe2O3 due to tin (Sn) diffusion from the bottom FTO substrate. Upon identifying the unfavorable interaction between the unintentional dopant Sn4+ and intentional dopant P5+, we have developed a straightforward P-doping method. The resulting P:Sn:Ti-Fe2O3 (P:Sn:Ti triple-doped Fe2O3) exhibits a remarkable improvement in photocurrent density, reaching 3.44 mA cm−2 at 1.23 VRHE, surpassing values reported in previous P-doping hematite studies. Following co-catalyst deposition, the NiFeOx/P:Sn:Ti-Fe2O3 photoanode achieves a maximum photocurrent density of 4.30 mA cm−2 at 1.23 VRHE. This study affirms that suppressing the negative interaction between dopants is crucial for significantly enhancing PEC performance.

Boosting visible-light response for the complete decomposition of volatile organic compounds on the Cu-oxide deposited WO3 photocatalyst by the synergistic effects of TiO2

The degradation of volatile organic compounds (VOCs) by photocatalytic systems is the most practical strategy due to its cost performance, simplicity, and environmental sustainability. To address such issues, the photocatalytic activities of tungsten trioxide (WO3) were developed by the deposition of various cocatalysts. In particular, the Cu-oxide (CuO/Cu2O)-deposited WO3 (Cu-WO3) photocatalyst could efficiently decompose acetic acid and acetaldehyde into CO2 under visible-light irradiation, although it exhibited low activity for the decomposition of benzene, toluene and xylene (BTX). Furthermore, a composite Cu-WO3/TiO2 photocatalytic system, which was fabricated by the simple physical mixing of Cu-WO3 with TiO2, was found to exhibit unprecedented reactivity for the complete decomposition of persistent BTX pollutants into CO2 under visible light irradiation. The synergistic effects of Cu-WO3 and the interfacial surface complex (ISC) formed by toluene-adsorbed TiO2 contribute to the efficient visible light response by excitation up to around 600 nm. The reaction mechanism for the enhancement of photocatalytic activity by the Cu-WO3/TiO2 composite photocatalyst is examined in this study.

Subtraction Descriptors in Machine Learning for Optimizing the Cocatalyst Effect of Cobalt Phosphate on Hematite Photoanodes.

In the quest for sustainable energy solutions, the optimization of the photoelectrochemical (PEC) performance of hematite photoanodes through cocatalysts represents a promising avenue. This study introduces a novel machine learning approach, leveraging subtraction descriptors, to isolate and quantify the specific effects of cobalt phosphate (Co-Pi) as a cocatalyst on hematite's PEC performance. By integrating data from various analytical techniques, including photoelectrochemical impedance spectroscopy and ultraviolet-visible spectroscopy, with advanced machine learning models, we successfully predicted the PEC performance enhancement attributed to Co-Pi. The Gaussian process regression (GPR) model emerged as the most effective, revealing the critical influence of the interfacial resistance, bulk resistance, and interfacial capacitance on the PEC performance. These findings underscore the potential of cocatalysts in improving charge separation and extending charge carrier lifetimes, thereby boosting the efficiency of photocatalytic reactions. This study not only advances our understanding of the cocatalyst effect in photocatalytic systems but also demonstrates the power of machine learning in modifying complex materials and guiding the development of optimized photocatalytic materials. The implications of this research extend beyond hematite photoanodes, offering a generalizable framework for enhancing the photoelectrochemical properties of a wide range of material modifications such as cocatalyst deposition, doping, and passivation.

Deposition state of CoS significantly affects the photocatalytic H2 generation performance of CdS–CoS heterostructure

Activity and stability are two scientific issues of concern in catalyst design and synthesis. In this study, supported (CoS/CdS) and encapsulated (CdS@CoS) catalysts were synthesized with controlled variations in solvent. Remarkably, the CoS/CdS exhibited higher activity, achieving an impressive average H2 generation rate of 29.26 mmol g−1 h−1 for the optimized sample. Conversely, the CdS@CoS demonstrated superior stability, showing no significant activity decline over a 20-h period. These findings highlight the importance of the cocatalyst deposition state in affecting the photocatalytic performance of catalysts. This research provides valuable insights for the synthesis of photocatalysts.

Dual Shield: Bifurcated Coating Analysis of Multilayered WO3/BiVO4/TiO2/NiOOH Photoanodes for Sustainable Solar-to-Hydrogen Generation from Challenging Waters.

The heterostructure WO3/BiVO4-based photoanodes have garnered significant interest for photoelectrochemical (PEC) solar-driven water splitting to produce hydrogen. However, challenges such as inadequate charge separation and photocorrosion significantly hinder their performance, limiting overall solar-to-hydrogen conversion efficiency. The incorporation of cocatalysts has shown promise in improving charge separation at the photoanode, yet mitigating photocorrosion remains a formidable challenge. Amorphous metal oxide-based passivation layers offer a potential solution to safeguard semiconductor catalysts. We examine the structural, surface morphological, and optical properties of two-step-integrated sputter and spray-coated TiO2 thin films and their integration onto WO3/BiVO4, both with and without NiOOH cocatalyst deposition. The J-V experiments reveal that the NiOOH cocatalyst enhances the photocurrent density of the WO3/BiVO4 photoanode in water splitting reactions from 2.81 to 3.87 mA/cm2. However, during prolonged operation, the photocurrent density degrades by 52%. In contrast, integrated sputter and spray-coated TiO2 passivation layer-coated WO3/BiVO4/NiOOH samples demonstrate a ∼88% enhancement in photocurrent density (5.3 mA/cm2) with minimal degradation, emphasizing the importance of a strategic coating protocol to sustain photocurrent generation. We further explore the feasibility of using natural mine wastewater as an electrolyte feedstock in PEC generation. Two-compartment PEC cells, utilizing both fresh water and metal mine wastewater feedstocks exhibit 66.6 and 74.2 μmol/h cm2 hydrogen generation, respectively. Intriguingly, the recovery of zinc (Zn2+) heavy metals on the cathode surface in the mine wastewater electrolyte is confirmed through surface morphology and elemental analysis. This work underscores the significance of passivation layer and cocatalyst coating methodologies in a sequential order to enhance charge separation and protect the photoanode from photocorrosion, contributing to sustainable hydrogen generation. Additionally, it suggests the potential of utilizing wastewater in electrolyzers as an alternative to freshwater resources.

In Situ Multicolor Imaging of Photocatalytic Degradation Process of Permanganate on Single Bismuth-Based Metal-Organic Frameworks.

Bismuth-based metal-organic frameworks (Bi-MOFs) have emerged as important photocatalysts for pollutant degradation applications. Understanding the photocatalytic degradation mechanism is key to achieving technological advantage. Herein, we apply dark-field optical microscopy (DFM) to realize in situ multicolor imaging of the photocatalytic degradation process of permanganate (MnO4-) on single CAU-17 Bi-MOFs. Three reaction kinetic processes such as surface adsorption, photocatalytic reduction, and disproportionation are revealed by combining the time-lapsed DFM images with optical absorption spectra, indicating that the photocatalytic reduction of purple MnO4- first produces beige red MnO42- through a one-electron pathway, and then MnO42- disproportionates into yellow MnO2 on CAU-17. Meanwhile, we observe that the deposition of MnO2 cocatalysts enhances the surface adsorption reaction and the photocatalytic reduction of MnO4- to MnO42-. Unexpectedly, it is found that isopropanol as a typical hole scavenger can stabilize MnO42-, avoiding disproportionation and causing the alteration of the photocatalytic reaction pathway from a one-electron avenue to a three-electron (1 + 2) process for producing MnO2 on CAU-17. This research opens up the possibility of comprehensively tracking and understanding the photocatalytic degradation reaction at the single MOF particle level.

Surface Engineered Single-atom Systems for Energy Conversion.

Single-atom catalysts (SACs) are demonstrated to show exceptional reactivity and selectivity in catalytic reactions by effectively utilizing metal species, making them a favorable choice among the different active materials for energy conversion. However, SACs are still in the early stages of energy conversion, and problems like agglomeration and low energy conversion efficiency are hampering their practical applications. Substantial research focus on support modifications, which are vital for SAC reactivity and stability due to the intimate relationship between metal atoms and support. In this review, a category of supports and a variety of surface engineering strategies employed in SA systems are summarized, including surface site engineering (heteroatom doping, vacancy introducing, surface groups grafting, and coordination tunning) and surface structure engineering (size/morphology control, cocatalyst deposition, facet engineering, and crystallinity control). Also, the merits of support surface engineering in single-atom systems are systematically introduced. Highlights are the comprehensive summary and discussions on the utilization of surface-engineered SACs in diversified energy conversion applications including photocatalysis, electrocatalysis, thermocatalysis, and energy conversion devices. At the end of this review, the potential and obstacles of using surface-engineered SACs in the field of energy conversion are discussed. This review aims to guide the rational design and manipulation of SACs for target-specific applications by capitalizing on the characteristic benefits of support surface engineering.

Nanostructured Fe2TiO5 photoanode with enhanced photoelectrochemical water splitting performance by Zn2+ doping and FeNi(OH)x cocatalyst deposition

Combining heteroatom doping and cocatalyst deposition by facile electrospray offers an effective strategy for developing high performance photoanode.

Development of a Simple Ink Coating Procedure for BiVO4 Photoanodes for Oxygen Evolution

Photoelectrodes can be implemented in electrochemical cells to accelerate the reaction kinetics of the intended reactions, utilizing the support of visible light. Especially, photoanodes for the oxygen evolution reaction (OER) are of great interest for energy storage and conversion, since the OER is the anodic half-cell reaction of many Power-to-X technologies such as water splitting, CO2 electroreduction and metal-air battery recharge. However, the OER still limits their potential by being a kinetically hindered 4-electron transfer process. In previous research, bismuth vanadate (BiVO4) has shown significant advances for the onset potential and increase in current density of the OER under illumination. Additionally, BiVO4 is a low-cost material, making it favorable over commonly used noble metal electrocatalysts, leading to its rise as one of the most suitable photoelectrocatalysts for OER photoanodes. However, BiVO4 still does not match practical requirements, demanding for further research and development.In this work, we focus on the implementation of a simple ink coating procedure for BiVO4 photoanodes. Ink coating demonstrates a versatile and adaptable preparation procedure for photoelectrodes, since photoelectrocatalyst synthesis and catalyst deposition are decoupled, providing a large degree of preparative freedom. On the one hand, the catalyst synthesis can be modified and adjusted separately. On the other hand, the catalyst deposition can be performed via various techniques using an ink. Thus, the photoelectrode preparation is not restricted to a certain substrate and specific synthesis conditions.In the proposed ink coating procedure, first neat and (Mo or W)-doped BiVO4 photoelectrocatalysts are prepared via hydrothermal synthesis also including Co-Pi as a post-deposited co-catalyst. Afterwards, the resulting catalysts are deposited onto FTO glass for further physico-chemical characterization. Moreover, the photoelectrochemical (PEC) performance under illumination and in the dark is investigated for the prepared electrodes. Finally, the ink coated electrodes are compared to BiVO4 photoanodes, which are prepared via solution-based methods, as reported in literature.[1-4] For the physico-chemical analysis, the ink coated photoanodes are characterized by various microscopic and spectroscopic techniques. SEM images reveal that homogeneous catalyst layers are prepared. Additionally, LSM measurements show that ink coating leads to a catalyst layer with a high surface roughness. XRD and Raman measurements reveal crystalline and pure BiVO4 structures. Furthermore, for the investigation of the PEC performance, an H-cell which is equipped with an LED light source is utilized, allowing for rapid and flexible data acquisition at constant temperatures. In the photoelectrochemical measurements, a significant reduction of the OER onset potential as well as a significant increase in photocurrent density in comparison to dark scans is achieved for neat BiVO4 photoanodes. For now, the ink coated BiVO4 could lower the onset potential by up to 0.6 V under illumination and increase the current density by up to 10 mA/cm² in comparison to the dark scans. In addition, modification of the ink coated BiVO4 by doping and co-catalyst deposition results in an even higher enhancement of the PEC performance for the OER. At this, the ink coated catalyst layers show an excellent stability even after several hours of PEC measurements. Moreover, it is shown that the ink coated BiVO4 photoanodes perform well in comparison to the solution coated electrodes. Overall, the ink coating procedure was successfully established for BiVO4 photoanodes, opening the door for the adaptation to the electrode preparation for different Power-to-X technologies. Literature: [1] B. Pattengale, J. Ludwig, J. Huang, J. Phys. Chem. C 2016, 120, 1421.; [2] S. K. Choi, W. Choi, H. Park, Phys. Chem. Chem. Phys. 2013, 15, 6499.; [3] J. A. Seabold, K.-S. Choi, J. Am. Chem. Soc. 2012, 134, 2186.; [4] K. J. McDonald, K.-S. Choi, Energy Environ. Sci. 2012, 5, 8553.

Scaling up BiVO4 Photoanodes on Porous Ti Transport Layers for Solar Hydrogen Production.

Commercialization of photoelectrochemical (PEC) water-splitting devices requires the development of large-area, low-cost photoanodes with high efficiency and photostability. Herein, we address these challenges by using scalable fabrication techniques and porous transport layer (PTLs) electrode supports. We demonstrate the deposition of W-doped BiVO4 on Ti PTLs using successive-ionic-layer-adsorption-and-reaction methods followed by boron treatment and chemical bath deposition of NiFeOOH co-catalyst. The use of PTLs that facilitate efficient mass and charge transfer allowed the scaling of the photoanodes (100 cm2 ) while maintaining ~90 % of the performance obtained with 1 cm2 photoanodes for oxygen evolution reaction, that is, 2.10 mA cm-2 at 1.23 V vs. RHE. This is the highest reported performance to date. Integration with a polycrystalline Si PV cell leads to bias-free water splitting with a stable photocurrent of 208 mA for 6 h and 2.2 % solar-to-hydrogen efficiency. Our findings highlight the importance of photoelectrode design towards scalable PEC device development.

Enhancing photocatalytic water splitting: Comparative study of TiO2 decorated nanocrystals (Pt and Cu) using different synthesis methods

The use of light radiation to cause the dissociation of water into hydrogen (H2) gas has tremendous promise as a green method of hydrogen production. Herein, we reported a comparative study for the photocatalytic activity of TiO2 nanocomposite with two co-catalysts e.g., Pt or Cu nanocrystals (3–4 nm) using different synthesis procedures; incipient wet impregnation (Imp), hydrothermal (HT), or photo-deposition (PD) methods. The effect of catalyst mass loading percentages (0.1–1 wt.%) was investigated. The mass loading of 0.3 wt% for both co-catalysts exhibited the highest value of the generated hydrogen. Even without a precious metal such as Pt, Cu/TiO2 synthesized using the PD method provided an initial rate of 24 mmol h-1g−1, which is 3.5 and 1.4 times higher than the composite synthesized using HT and Imp methods. On the other hand, the highest rate for Pt co-catalyst was observed for the Imp method with a rate of 58 mmol h-1g−1 which was higher by 1.6 and 1.1 times than the composite synthesized using PD and HT methods, respectively. This study offers new perspectives on the significant influence of the co-catalyst deposition technique on the efficiency of photocatalysis for producing hydrogen through water splitting.

Surface‐modified Ag@Ru‐P25 for photocatalytic CO2 conversion with high selectivity over CH4 formation at the solid–gas interface

AbstractSystematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO2 reduction to solar fuels. A surface‐modified Ag@Ru‐P25 photocatalyst with H2O2 treatment was designed in this study to convert CO2 and H2O vapor into highly selective CH4. Ru doping followed by Ag nanoparticles (NPs) cocatalyst deposition on P25 (TiO2) enhances visible light absorption and charge separation, whereas H2O2 treatment modifies the surface of the photocatalyst with hydroxyl (–OH) groups and promotes CO2 adsorption. High‐resonance transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray absorption near‐edge structure, and extended X‐ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst, while thermogravimetric analysis, CO2 adsorption isotherm, and temperature programmed desorption study were performed to examine the significance of H2O2 treatment in increasing CO2 reduction activity. The optimized Ag1.0@Ru1.0‐P25 photocatalyst performed excellent CO2 reduction activity into CO, CH4, and C2H6 with a ~95% selectivity of CH4, where the activity was ~135 times higher than that of pristine TiO2 (P25). For the first time, this work explored the effect of H2O2 treatment on the photocatalyst that dramatically increases CO2 reduction activity.

Photoinduced deposition of AuCu cocatalyst and polyaniline conducting layer on graphitic-C3N4 for enhanced CO2 photoreduction

Photocatalytic CO2 conversion into solar fuel is of great significance for addressing energy crisis and climate change, but this process is generally hampered by insufficient electron deliverability and sluggish reaction kinetics. Herein, polyaniline (PANI) conducting layer and AuCu alloy cocatalyst are successively deposited on graphitic carbon nitride (g-C3N4) nanoflakes via a two-step photoinduced process, to fabricate an AuCu/PANI/g-C3N4 heterostructure photocatalyst. The presence of PANI layer improves electron deliverability and CO2 adsorption capacity of photocatalyst. The AuCu cocatalyst affords efficient active sites for accelerating the reaction kinetics of CO2 photoreduction, and the surface plasmon resonance (SPR) of Au further enhances light utilization and charge separation. Benefiting from these merits, the AuCu/PANI/g-C3N4 photocatalyst exhibits a superior performance toward CO2 reduction with 100% CO selectivity, affording a CO production rate of 9.2 μmol·gcat−1·h−1 under simulated sunlight, which is 1.3 times that from AuCu/g-C3N4 and 2.3 times that from PANI/g-C3N4, respectively. The photocatalytic CO2 reduction mechanism of AuCu/PANI/g-C3N4 catalyst is investigated by a series of control experiments and in-situ infrared spectroscopy. This study demonstrates a rational construction of heterogeneous photocatalysts and highlights the synergistic effect of multiple components in enhancing CO2 photoreduction.

Coupling surface modification with cocatalyst deposition on BiVO4 photoanode to enhance charge transfer for efficient solar-driven water splitting

Bismuth vanadate (BiVO4) has attracted wide attention as photoanode in water-splitting photoelectrochemical (PEC) devices. However, its catalytic performance is greatly limited by the serious charge recombination on the surface states. Herein, borate modified BiVO4 plus additional CoPi cocatalyst (B-BVO/CoPi) is developed as photoanode for PEC cell via a simple soaking and electrodeposition process. Based on the electrochemistry tests and material characteristics, the borate groups [B(OH)4] – is able to effectively prevent the charge recombination, while the outer CoPi cocatalyst enhance the activity toward oxygen evolution reaction. Therefore, the designed B-BVO/CoPi photoanode could obtain a high current density of 2.67 mA cm−2 at 1.23 VRHE with an onset potential of 0.29 VRHE, much higher than pristine BiVO4 (0.78 mA cm−2, 0.52 VRHE). This work may provide a new insight for constructing multifunctional modified photoanodes for efficient solar conversion.

Effect of cyclic voltammetry on the deposition of Ni cocatalyst on CuInS2 photoelectrode for water splitting under solar light irradiation

Effect of cyclic voltammetry on the deposition of Ni cocatalyst on CuInS2 photoelectrode for water splitting under solar light irradiation