Search

Photogenerating charges with long lifetimes to drive catalysis is challenging in organic semiconductors. Here, the role of a PM6 polymer overlayer on the photoexcited carrier dynamics is investigated in a Y6:PM6 bulk‐heterojunction (BHJ) photoanode undergoing ascorbic acid oxidation. With the additional polymer layer, the hole lifetime is increased in the solid state BHJ film. When the photoanode is electrically coupled to a hydrogen‐evolving platinum cathode, remarkably long‐lived hole polaron states are observed on the timescale of seconds under operational conditions. It is demonstrated that these long‐lived holes enable the organic photoanode with the polymer overlayer to show enhanced ascorbic acid oxidation performance, reaching ≈7 mA cm−2 at 1.23 VRHE without a co‐catalyst. An external quantum efficiency of 18% is observed using 850 nm excitation. It is proposed that the use of an organic overlayer can be an effective design strategy for generating longer charge carrier lifetimes in organic photoanodes for efficient oxidation catalysis. [ABSTRACT FROM AUTHOR]

Steam-electrolysis performance of protonic ceramics cells with Ni-cermet and triple-component composite electrodes composed of protonic ceramics, mixed proton–electron conductor, and catalysts was evaluated under different operating atmospheres at 500 °C to determine the effects of the catalysts on the electrode performance and electrochemical reaction mechanisms of steam splitting and hydrogen evolution. Here, Ba(Ce 0.3 Zr 0.5 Y 0.1 Yb 0.1)O 3-δ , (Ba 0.95 La 0.05) (Fe 0.8 Zn 0.2)O 3-δ , and La 0.8 Sr 0.2 CoO 3-δ were used as the protonic ceramics, mixed proton–electron conductor, and catalyst, respectively. Under a fuel-cell atmosphere, the steam vapor pressure (p H 2 O) at the airside and hydrogen partial pressure (p H 2) at the fuel side were held constant at equal levels. In contrast, p H 2 O was higher and p H 2 was lower under the electrolysis atmosphere. The higher p H 2 O at the airside decreased the air electrode impedance, but the lower p H 2 at the fuel side significantly increased the fuel electrode impedance. The La 0.8 Sr 0.2 CoO 3-δ catalyst facilitated the adsorption and dissociation of steam. Based on the study results, the mechanisms for steam splitting/dissociation at the triple-component composite electrode and hydrogen evolution at the Ni-cermet electrode are suggested. • A triple-component composite electrode with LSC is used for steam electrolysis. • LSC catalyst improves an electrode performance in electrolysis mode. • PCEC performance becomes worse with decreasing p H 2 of fuel. • Steam splitting mechanism at a triple-component composite electrode is suggested. • Mechanism for hydrogen evolution using a dihydrogen cation is suggested. [ABSTRACT FROM AUTHOR]

Hydrogen is an essential energy carrier which will address the challenges posed by the energy crisis and climate change. Photoelectrochemical water splitting (PEC) is an important method for producing solar-powered hydrogen. The PEC tandem configuration harnesses sunlight as the exclusive energy source to drive both the hydrogen (HER) and oxygen evolution reactions (OER), simultaneously. Therefore, PEC tandem cells have been developed and gained tremendous interest in recent decades. This review describes the current status of the development of tandem cells for unbiased photoelectrochemical water splitting. The basic principles and prerequisites for constructing PEC tandem cells are introduced first. We then review various single photoelectrodes for use in water reduction or oxidation, and highlight the current state-of-the-art discoveries. Second, a close look into recent developments of PEC tandem cells in water splitting is provided. Finally, a perspective on the key challenges and prospects for the development of tandem cells for unbiased PEC water splitting are given. [ABSTRACT FROM AUTHOR]

Producing solar fuels through semiconductor‐based photocatalytic water splitting is one of the main options for worldwide employment of non‐fossil energy sources. Nonetheless, the relatively low efficiency of the known photocatalysts, the high prices of composing elements, and the costly preparation methods render expensive devices that would not be economically competitive with fossil energy sources. Herein, we present a facile method for the preparation of both round hematite (Fe2O3) nanoparticles, with average diameter of (56±7) nm, and of niobium‐doped hematite nanoparticles with similar size and morphology. Thin films of these nanoparticles were assembled through electrophoretic deposition, resulting in homogeneous photoanodes with nanometer thickness that can split water, under simulated solar irradiation, to produce oxygen in a photoelectrochemical cell. The optimization of the film composition and thickness resulted in the improvement of the photocurrent from 352.3 to 1,342.5 μA cm−2 at 1.23 V vs RHE for the pristine hematite and Nb‐doped hematite, respectively, both with thickness of (499±63) nm. This enhancement in the oxidation reaction yield is a clear consequence of the improvement of charge carriers transport along the nanoparticle structure due to niobium doping and adequate light absorption/charge transfer balance of the photoelectrode under operation. [ABSTRACT FROM AUTHOR]

Constructing nanostructures that fully boost the performance of all metals while offering a positive inter‐particle effect among frameworks is an efficient approach for enhancing electrochemical effectiveness. Elongated In : SnO2/La4NiS7 structure is created using diethyl dithiocarbamate complex. Investigations were done on the material's surficial, crystallographical and electrochemical characters. The direct optical band gap as determined by UV‐visible analysis was 2.9 eV. X‐ray photoelectron spectroscopy presented La3d and Ni2p core level. Electrical investigations of the transparent photoactive electrode in a photoelectrochemical cell showed an exceptional specific capacity of 906 F ⋅ g−1 at 5 mV ⋅ s−1 under illumination. Transient chronoamperometric response of the photoelectrode presented 35.3 mA photocurrent generation. Greater photocurrents were achieved at all scan rates in the existence of light indicating that the exposure to light positively impacted the electrode's performance. Undoubtedly, this work proposed a beneficial photoelectrode that's applicable to systems that generate electricity from renewable sources. [ABSTRACT FROM AUTHOR]

Since 2015, a number of breakthroughs in the generation of new MAX phases using specified double transition metals have made possible the synthesis of unique MXenes with significant chemical diversity and structural complexity, which are rare in 2D families. MXene and semiconductor hybrids are shown to be effective photocatalysts because to their unique interface features. For photocatalytic purposes, a Schottky heterojunctions may provide faster charge separation and a lower Schottky barrier. When it comes to photocatalytic and photo electrochemical applications, photocatalysts are predicted to be the greatest and most popular new photocatalysts. We discussed some of the semiconductor-based nanocomposites supported by MXenes, including photocatalytic and photo electrochemical water splitting. Next, we discussed some of the difficulties and opportunities that have arisen from working with MXenes to advance semiconductor-based photocatalysts. Scientists in related fields are noticed to prompt the development of novel photocatalysts based on semiconductors. [Display omitted] • The effects of MXenes hybrids as emerging Photocatalysts and PEC catalysts for water splitting. • Structural and preparation of MXenes are elaborated. • The difficulties and opportunities from working with MXenes to advance semiconductor based photocatalysts. • Perspective challenges for water splitting efficiency improvement are mentioned. [ABSTRACT FROM AUTHOR]

Water splitting technology is an innovative strategy to face the dependency on fossil fuels and, at the same time, address environmental pollution issues. Electrocatalysts seem to be the better option to improve water separation efficiency and satisfy the commercial-scale demand for hydrogen. Therefore, the design and fabrication of heterostructures with a high affinity for achieving water splitting have been proposed. In this review, the application of several electrocatalysts for hydrogen and oxygen evolution reactions is presented and discussed in detail. A review of the recent advances in water separation using noble metals such as Pt-, Ir-, and Ru-based electrodes is presented, followed by a highlighting of the current trends in noble-metal-free electrocatalysts and novel preparation methods. Furthermore, it contemplates some results of a hybrid organic molecule–water electrolysis and photoelectrochemical water splitting. This review intends to give insight into the main trends in water splitting and the barriers that need to be overcome to further boost the efficiency of the main hydrogen and oxygen generation systems that ultimately result in large-scale applications. Finally, future challenges and perspectives are addressed, considering all the novelties and the proposed pathways for water splitting. [ABSTRACT FROM AUTHOR]

Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field. [ABSTRACT FROM AUTHOR]

This paper discusses about a facile transition metal tungstate thin films preparation method and their remarkable photoelectrochemical properties. The films of AWO4 (A2+ = Fe, Co, Ni, Cu) were deposited onto conductive fluorine-doped tin oxide (FTO) glass substrate. The results of X-ray diffraction analysis indicated the presence of crystalline films. Field emission scanning electron microscopy images revealed nanostructured materials. X-ray photoelectron studies were employed to analyze elemental and chemical composition. Optical behavior indicated indirect transitions for all AWO4 films. Photoelectrochemical studies displayed that AWO4 films were successfully used as photoanodes in a photoelectrochemical cell under polychromatic irradiation. From electrochemical measurement, it was possible to estimate the flat band potential and so prevising suitable application of photoelectrodes. This work reports for the first time a comparative and comprehensive photoelectrochemical study with AWO4 films prepared in a simple way. The results indicate that the films can be used as photoanodes in water splitting reactions and other photoelectrocatalytic applications. [ABSTRACT FROM AUTHOR]

The present work reports the photoelectrocatalytic properties of pyrolyzed molybdenum oxide thin film. Microstructural analysis revealed clustered nanoaggregates. Structural analysis showed a polycrystalline α -MoO3 phase. The crystallite size, dislocation density, microstrain, and stacking faults were found to be 41.27 nm, 5.87 × 10−4 lines/cm2, 8.41 × 10−4 and 1.78, respectively. The optical bandgap was found to be 3.20 eV. Linear sweep voltammetry measurement in 1 M KOH electrolyte revealed a significant photocurrent density of 992.39 μA/cm2 at a bias of 1.2 V versus Ag/AgCl (1.4 V vs. RHE). The reasonable performance of the device suggests that the rarely deployed spray pyrolysis method is promising for preparing photoactive α -MoO3 films for photoelectrochemical measurement. [ABSTRACT FROM AUTHOR]

In this work, hierarchical WO3 microspheres were synthesized using chemical bath deposition. The morphology of the synthesized sample was studied using scanning electron microscopy (SEM). The hierarchical WO3 microspheres formed from spontaneously self-assembled nanosheets have a high specific surface area. Structural characterizations of sample were performed using X-ray diffraction (XRD) and Raman spectroscopy. Analysis of XRD spectra showed that synthesized particles have a monoclinic modification. The optical properties of the sample were studied using UV-Vis diffuse reflectance absorption spectra. The value of the energy gap calculated from the absorption spectra is 2.25 eV, which indicates high light absorption ability. A photocurrent study was done to investigate the photocatalytic activity. The photoelectrode was prepared using hierarchical WO3 microspheres and polymer deposited on fluorine doped tin oxide (FTO) glass via spin coating technique. A remarkable photocurrent density of 18 A/cm2 at 0.5 V was achieved. The elongated structures improved light absorption ability and photocatalytic activity, and might be perspective as photoanode in photoelectrochemical cells. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is one of the important chemicals for human life. The demand for ammonia is expected to increase every year. Conventionally, the fixation process of N2 to produce NH3 in the industrial sector is carried out through the Haber-Bosch process, which requires extreme temperature and pressure conditions that consume a high amount of energy and emit a considerable amount of CO2. Therefore, it is necessary to develop alternative technology to produce ammonia using environmentally friendly methods. Many studies have developed the photoelectrochemical conversion of nitrogen to ammonia in the presence of semiconductor materials, but the resulting efficiency is still not as expected. In this research, the development of the tandem system of Dye-Sensitized Solar Cell - Photoelectrochemistry (DSSC - PEC) was carried out for the conversion of nitrogen to ammonia. The DSSC cell was prepared using N719/TiO2 nanotubes as photoanode, Pt/FTO as cathode, and electrolyte I-/I3 -. The DSSC efficiency produced in this research was 1.49%. PEC cell at the cathode and anode were prepared using BiOBr/TiO2 nanotubes synthesized by the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The resulting ammonia levels were analyzed using the phenate method. In this study, ammonia levels were obtained at 0.1272 µmol for 6 hours of irradiation with an SCC (Solar to Chemical Conversion) percentage of 0.0021%. [ABSTRACT FROM AUTHOR]

Herein, we successfully fabricated an Al-doped α-Ga2O3 nanorod array on FTO using the hydrothermal and post-annealing processes. To the best of our knowledge, it is the first time that an Al-doped α-Ga2O3 nanorod array on FTO has been realized via a much simpler and cheaper way than that based on metal–organic chemical vapor deposition, magnetron sputtering, molecular beam epitaxy, and pulsed laser deposition. And, a self-powered Al-doped α-Ga2O3 nanorod array/FTO photodetector was also realized as a photoanode at 0 V (vs. Ag/AgCl) in a photoelectrochemical (PEC) cell, showing a peak responsivity of 1.46 mA/W at 260 nm. The response speed of the Al-doped device was 0.421 s for rise time, and 0.139 s for decay time under solar-blind UV (260 nm) illumination. Compared with the undoped device, the responsivity of the Al-doped device was ~5.84 times larger, and the response speed was relatively faster. When increasing the biases from 0 V to 1 V, the responsivity, quantum efficiency, and detectivity of the Al-doped device were enhanced from 1.46 mA/W to 2.02 mA/W, from ~0.7% to ~0.96%, and from ~6 × 109 Jones to ~1 × 1010 Jones, respectively, due to the enlarged depletion region. Therefore, Al doping may provide a route to enhance the self-powered photodetection performance of α-Ga2O3 nanorod arrays. [ABSTRACT FROM AUTHOR]

Wide‐bandgap perovskite solar cells (PSCs) are a promising technology with a series of potential applications, including tandem photovoltaics, solar‐driven electrochemical energetic devices, and outfit morphing power supply for underwater equipment. However, the energy‐level difference between the charge transport layer and perovskite may result in inefficient interfacial charge extraction, leading to the series carrier accumulation at the interface that impairs the photovoltaic performance. Herein, [6,6]‐phenyl C61 butyric acid methyl ester is introduced between SnO2 and FAPbBr3 to alleviate the energy‐level mismatch. Significant photoluminescence quenches and decreased series resistance both verify the promoted interfacial charge extraction efficiency. Besides, the film on the flattened nonwetting electronic transport layers film has better quality, thus reducing defect density and nonradiative recombination. As a result, a 20% power conversion efficiency (PCE) improvement, from 7.02% to 8.55%, is achieved under AM1.5G illumination. More importantly, for the first time, this work demonstrates a highly efficient PSC with a PCE over 43% under the 532 nm laser condition, providing a promising wireless fast charging way with high‐power laser irradiation in deep ocean. [ABSTRACT FROM AUTHOR]

Spin coating from a single source precursor is used to produce a transparent conductive electrode for a photoelectrochemical cell. Yb2S3:Cu2S:ZnS is discovered in the composite using X‐ray diffraction analysis with a crystallite size of 44 nm. Energy‐dispersive X‐ray analysis and X‐ray photoelectron spectroscopy reveal that the composite comprises Yb, Cu, Zn, and S with an optical bandgap of 2.49 eV. Electrical investigations in a photoelectrochemical cell are measured using cyclic voltammetry, linear sweep voltammetry, transient chronoamperometry (CA), and electrical impedance spectroscopy (EIS). Every experiment shows that the photocurrent density of the electrode is higher than when it is in the light. At all scan rates, light causes the photoelectrode's specific capacitance to increase. Specific capacitance is found to have a maximum value under illumination of 789 Fg−1 as opposed to 745 Fg−1 in the absence of a light source. The highest photocurrent density achieved by the electrode through CA is 23.5 mA. Rs value of 23.4 Ω is subsequently obtained by the EIS investigation. It might be stated that this work introduces a useful photoelectrode that can be used in renewable energy systems such as photovoltaics, supercapacitors, and photoelectrochemical solar cells. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Laser is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BiVO4 possesses a suitable band gap for photoelectrochemical (PEC) water splitting to produce hydrogen; however, the performance of BiVO4 is limited by several adverse factors. The bulk charge recombination and the slow surface water oxidation reaction of BiVO4 are main unfavorable factors. In view of these disadvantages, an Fe–Bi electrocatalyst is loaded on BiVO4 to improve the PEC performance of BiVO4. After modification, the onset potential of BiVO4 shifts negatively by 60 mV, and the saturated photocurrent is greatly increased. Systematic studies demonstrate that the Fe–Bi electrocatalyst not only enhances the bulk charge separation, but also accelerates the surface water oxidation rate of BiVO4 and greatly reduces the resistance of the reaction interface. [ABSTRACT FROM AUTHOR]

Photoelectrochemical lithium (Li) extraction can be expected to provide a useful recycle of Li+ from waste Li‐containing battery, but the process is limited by the photocathodes with poor Li+ absorption and low yield rate. Here, we have designed a hierarchical silicon (Si)‐based photocathode with mixed‐phase tungsten oxide (WO3) cocatalysts for photoelectrochemical Li extraction under 1 sun illumination, achieving a high Li yield rate of ≈223.0 μg cm−2 h−1 and an excellent faradaic efficiency of 91.9 % at 0.0817 V versus Li0/+ redox couple. The WO3 cocatalysts with the mixture of amorphous and crystalline phase accelerates the Li+ insertion and precipitation and enriches the concentration of Li+ at the photocathode surface. This robust photoelectrochemical Li extraction system provides a new insight on designing green and efficient route for cyclic utilization of Li resources in the sustainable energy field. [ABSTRACT FROM AUTHOR]

In order to improve the conversion and transmission efficiency of the photoelectron, core–shell spheroid structure titanium dioxide/cadmium sulfide (TiO2/CdS) composites were synthesized as epoxy-based coating fillers using a simple hydrothermal method. The electrochemical performance of photocathodic protection for the epoxy-based composite coating was analyzed by coating it on the Q235 carbon steel surface. The results show that the epoxy-based composite coating possesses a significant photoelectrochemical property with a photocurrent density of 0.0421 A/cm2 and corrosion potential of −0.724 V. Importantly, the modified composite coating can extend absorption in the visible region and effectively separate photoelectron hole pairs to improve the photoelectrochemical performance synergistically, because CdS can be regarded as a sensitizer to be introduced into TiO2 to form a heterojunction system. The mechanism of photocathodic protection is attributed to the potential energy difference between Fermi energy and excitation level, which leads to the system obtaining higher electric field strength at the heterostructure interface, thus driving electrons directly into the surface of Q235 carbon steel (Q235 CS). Moreover, the photocathodic protection mechanism of the epoxy-based composite coating for Q235 CS is investigated in this paper. [ABSTRACT FROM AUTHOR]

Photoelectrochemical and photocatalytic reactions are extensively investigated in terms of artificial photosynthesis as well as environmental purification, where the application of a photoelectrode (or a photocatalyst) responding to visible light for a targeted reaction is desired towards the massive decomposition to products. Cadmium sulfide (CdS) has attracted attention as one of the promising candidates, owing to its narrow band gap and large absorption coefficient. In the present work, CdS photoelectrode was prepared for the first time by chemical bath deposition process, especially with multiple deposition steps. When it was utilized as the photoanode in the presence of S2−, the steady-state photocurrents of the multi-deposited CdS were much higher than that of the single-deposited one. The above improvement was attributable to an increase in surface area originating in the formation of porous structure. In addition, the multi-deposited CdS got thicker on the vertical direction to electrode substrate, causing the redshift of its absorption edge, and thus enhancing the photoanodic output. This work provides a novel and effective approach for fabricating CdS photoelectrode. [ABSTRACT FROM AUTHOR]

CdS thin films were grown on an FTO substrate at different temperatures, employing the low-cost hydrothermal method. All the fabricated CdS thin films were studied using XRD, Raman spectroscopy, SEM, PL spectroscopy, a UV–Vis spectrophotometer, photocurrent, Electrochemical Impedance Spectroscopy (EIS), and Mott–Schottky measurements. According to the XRD results, all the CdS thin films were formed in a cubic (zinc blende) structure with a favorable (111) orientation at various temperatures. The Scherrer equation was used to determine the crystal size of the CdS thin films, which varied from 25 to 40 nm. The SEM results indicated that the morphology of thin films seems to be dense, uniform, and tightly attached to the substrates. PL measurements showed the typical green and red emission peaks of CdS films at 520 nm and 705 nm, and these are attributable to free-carrier recombination and sulfur vacancies or cadmium vacancies, respectively. The optical absorption edge of the thin films was positioned between 500 and 517 nm which related to the CdS band gap. For the fabricated thin films, the estimated Eg was found to be between 2.50 and 2.39 eV. According to the photocurrent measurements, the CdS thin films grown were n-type semiconductors. As indicated by EIS, resistivity to charge transfer (RCT) decreased with temperature, reaching its lowest level at 250 °C. Flat band potential and donor density were found to fluctuate with temperature, from 0.39 to 0.76 V and 4.41 × 1018 to 15.86 × 1018 cm−3, respectively, according to Mott–Schottky measurements. Our results indicate that CdS thin films are promising candidates for optoelectronic applications. [ABSTRACT FROM AUTHOR]

A photo-sensitizer made of graphene-based material (2-D) is used in concert with EDTA in photoelectrochemical solar cells to increase efficiency and storage capacity of solar energy in order to make a solar cell economically feasible. Photopotential and photocurrent are created at 1142mV and 960 μA, respectively. Photoelectrochemical cell have achieved a maximum power of 228.40 μW, a fill factor of 0.17, and a conversion efficiency of 4.38%. The cell storage capacity allows for a half power (t1/2) level to be maintained for 1300 minutes. The electrical output of the photoelectrochemical cell has been observed to be influenced by a number of different factors. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Electrochemistry is the property of Journal of Electrochemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The sluggish oxygen evolution reaction (OER) kinetics and adverse charge transfer and stability at the multi‐interfaces from Si to electrolyte severely impede the application of Si photoanodes. Herein, oxygen vacancy (OV)‐rich NiFe‐layered hydroxides (NiFe‐OH) nanosheet arrays are vertically orientated on Ni‐protected Si photoanodes by a facile solvothermal method followed by a hot Fe ion‐exchange treatment. By virtue of the formation of OVs on NiFe‐OH nanosheets and the vertical contact between the NiFe‐OH and Si substrate, the as‐prepared Si photoanode not only enables abundant active sites for OER but also boosts charge and mass transfer when compared to traditional electro‐deposit samples. Moreover, the vertical contact of NiFe‐OH on Ni/Si benefits to release the interfacial stress and thereby promotes the electrode stability. Consequently, the optimal Si photoanode shows an ultrahigh applied bias photon‐to‐current efficiency of 5.7% and a good stability of over 200 h, outdoing almost all of the recently reported Si photoanodes. [ABSTRACT FROM AUTHOR]

Herein, we present the decoration of NiFeCoAlOOH nanoparticles onto titanium doped nanoporous hematite (Ti-PH) utilizing a simple electroless ligand-controlled oxidation method for photoelectrochemical water splitting. Owing to the improved oxygen evolution reaction kinetics and reduced charge transfer resistance, the resulting Ti-PH/NiFeCoAlOOH photoanode presents an excellent photocurrent density of 2.46 mA/cm2 at 1.23 V vs. RHE and good stability compared to Ti-PH or bare hematite. Furthermore, the onset potential of the photocurrent density is shifted cathodically by ∼60 mV with reference to the titanium doped nanoporous hematite. This work offers a promising method for designing high-performance, stable, and inexpensive catalysts for photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

Monoclinic scheelite phase of n‐type bismuth vanadate (BiVO4) as a solar‐driven catalyst‐based photoanode is emerging as an optimistic approach for efficient photoelectrochemical water splitting because of features such as maximum light harvesting potential in visible spectrum, nontoxicity, earth abundance and stability under electrochemical conditions. The photoelectrochemical cell is a coherent and eco‐friendly technique to convert solar energy into a renewable energy source like hydrogen with zero carbon emissions. Here we fabricated nanocomposite‐based photoanodes RGO/CNT/BiVO4, RGO/CNT/Ni/BiVO4, RGO/CNT/Cu/BiVO4 and RGO/CNT/Ni/Cu/BiVO4 by layering reduced graphene oxide (RGO) and carbon nanotubes (CNTs) to act as a transmission channel for fast transport of electrons with non‐noble electrocatalyst nickel (Ni) and copper (Cu) nanoparticles and visible driven photoactive bismuth vanadate (BiVO4) nanomaterial on fluorine‐doped tin oxide by using electrodeposition and the drop casting method. The absorption edge was analyzed using ultraviolet–visible spectroscopy and Tauc plots, which clearly indicated a decreasing trend in the bandgap of BiVO4, thereby increasing the absorption spectrum with improved charge transfer rate. To scrutinize the proficiency of the electrochemical reaction during water splitting for hydrogen evolution reaction and oxygen evolution reaction of photoanodes, electrochemical testing was done using linear sweep voltammetry, which distinctly showed that the fabricated photoanode RGO/CNT/Ni/Cu/BiVO4 possessed high photo‐response at an overpotential of 190 mV, with a lower Tafel slope of 119 mV dec−1. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Nanostructured TiO2 is one of the best materials for photocatalysis, thanks to its high surface area and surface reactivity, but its large energy bandgap (3.2 eV) hinders the use of the entire solar spectrum. Here, it is proposed that defect‐engineered nanostructured TiO2 photocatalysts are obtained by hydrogenation strategy to extend its light absorption up to the near‐infrared region. It is demonstrated that hydrogenated or colored TiO2 hollow spheres (THS) composed of hierarchically assembled nanoparticles result in much broader exploitation of the solar spectrum (up to 1200 nm) and the engineered surface enhances the photogeneration of charges for photocatalytic processes. In turn, when applied for photodegradation of a targeted drug (Ciprofloxacin) this results in 82% degradation after 6 h under simulated sunlight. Valence band analysis by photoelectron spectroscopy revealed the presence of oxygen vacancies, whose surface density increases with the hydrogenation rate. Thus, a tight correlation between degree of hydrogenation and photocatalytic activity is directly established. Further insight comes from electron paramagnetic resonance, which evidences bulk Ti3+ centers only in hydrogenated THS. The results are anticipated to disclose a new path toward highly efficient photocatalytic titania in a series of applications targeting water remediation and solar fuel production. [ABSTRACT FROM AUTHOR]

TiO2 photoelectrodes modified with organic dyes with pyridine anchoring groups are prepared, which are used as photoanodes of dye-sensitized photoelectrochemical cells for efficient water reduction with high photocurrent density and stability in aqueous solutions. Vigorous H2 generation with a production rate of around 250 μmol h−1 is realized with a photoanode of an active area of 5 × 5 cm2. [ABSTRACT FROM AUTHOR]

Electrolysis of water is a sustainable route to produce clean hydrogen. Full water‐splitting requires a high applied potential, in part because of the pH‐dependency of the H2 and O2 evolution reactions (HER and OER), which are proton‐coupled electron transfer (PCET) reactions. Therefore, the minimum required potential will not change at different pHs. TEMPO [(2,2,6,6‐tetramethyl‐1‐piperidin‐1‐yl)oxyl], a stable free‐radical that undergoes fast electro‐oxidation by a single‐electron transfer (ET) process, is pH‐independent. Here, we show that the combination of PCET and ET processes enables hydrogen production from water at low cell potentials below the theoretical value for full water‐splitting by simple pH adjustment. As a case study, we combined the HER with the oxidation of benzylamine by anodically oxidized TEMPO. The pH‐independent electrocatalytic oxidation of TEMPO permits the operation of a hybrid water‐splitting cell that shows promise to perform at a low cell potential (≈1 V) and neutral pH conditions. [ABSTRACT FROM AUTHOR]

OER (oxygen evolution reaction) is a critical reaction in several storage and conversion systems for renewable and clean electrochemical energies, including solar fuel devices, metal–air batteries, as well as regenerative fuel and water splitting cells. Regarding the shortcomings of OER, apart from the sluggish kinetics and high reaction overpotential, the reaction rate and overpotential are difficult to be optimized simultaneously. Herein, a novel hierarchical particle–sheet-structured Fe-doped NixP electrocatalyst is developed, which presents abundant interfaces between crystalline particle and amorphous sheet. The OER overpotential is reduced to 204 mV at 20 mA cm−2 current density, while it is reduced to 225 and 231 mV at 100 and 300 mA cm−2, respectively. The Fe-doped NixP electrocatalyst also shows fast reaction kinetics, whose Tafel slope is a remarkable 25 mV dec−1. For an electrolytic cell whose cathode and anode are Pt/C/NF and Fe–NixP/NF, respectively, a mere 1.446 V voltage is necessary to drive a 10 mA cm−2 current density for achieving overall water-splitting property. Notably, it also works stably at considerably high current densities of 500 and 1000 mA cm−2, representing high potential for commercial applications. [ABSTRACT FROM AUTHOR]

Developing efficient semiconductor photoanodes demonstrating strong light absorption, efficient separation of photogenerated charge carriers, and reduced charge carrier recombination rate can benefit PEC water splitting. Integrating a wide band gap semiconductor with narrow bandgap material with suitable band alignment can enhance PEC performance. Herein, we have fabricated novel MoO3/γ-In2Se3 heterostructure photoanodes using RF magnetron sputtering. The films structural, optical, morphological, and elemental composition were investigated in detail using low-angle XRD, Raman spectroscopy, XPS analysis, EDAX, and FESEM. The XRD, Raman, XPS, and EDAX results strongly confirmed the presence of desired phases of MoO3 and γ-In2Se3 layers in heterostructure without forming any impurity or alloy. FESEM micrographs revealed a uniform, dense grain structure. Optical analysis of MoO3/γ-In2Se3 done by UV–Visible spectroscopy shows increased absorption compared to pristine-MoO3. Conduction and valence band-edge potential values indicate that MoO3/γ-In2Se3 films are suitable for PEC hydrogen production. The PEC performance of these heterostructure photoanodes was evaluated by performing LSV, Chronoamperometry, EIS, and Mott–Schottky analysis. LSV results of MoO3/γ-In2Se3 showed a 10-fold increase in photocurrent density and attained higher photoconversion efficiency (0.5%) compared to pristine-MoO3 photoanode. EIS analysis revealed that MoO3/γ-In2Se3 photoanodes had small charge transfer resistance. Investigation of Mott Schottky results shows carrier density increases from 2.8 × 1019 cm−3 to 2.1 × 1020 cm−3 after incorporating γ-In2Se3 over MoO3. An increase in time-dependent photocurrent density reveals that MoO3/γ-In2Se3 films have effective electron-hole separation. Our finding suggests that MoO3/γ-In2Se3-based heterostructure photoanode can enhance light harvesting capacity and suppresses carrier recombination rate, eventually boosting PEC performance. Moreover, these results encourage the development of highly efficient photoelectrodes based on heterostructures for solar water-splitting applications. [ABSTRACT FROM AUTHOR]

Combining multilayered structure, tunable physicochemical, and surficial properties, two-dimensional Ti3C2Tx MXene has been extensively investigated for their potential in field of noble-metal free electrocatalysis. However, easy aggregation of MXene nanosheets and their thermodynamic instability drastically reduce active sites and, hence, decline overall water-splitting efficiency. In this regard, approaches of surface engineering of MXene by introducing large-sized dopants have been acknowledged to overcome aforementioned issues. Considering this, herein, we have proposed a strategy for tuning MXene surface by substitutional vanadium doping, which induced additional accessible electrochemically active surface sites (V0+, V1+/2+, V3+, V4+, and V5+), along with inherent MXene sites (Ti2+, Ti3+, and Ti4+). This also inhibited inevitable self-restacking with minimal inherent aqueous oxidation. Vanadium doping has created abundant intimate heterointerface networks favoring electronic redistribution on conducting surface of MXene, thereby resulting in highly active sites, predominantly with low-valence (V0+ and Ti2+) and high-valence (V5+ and Ti4+) for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Benefitting from surficial synergistic features, optimized sample revealed superior bifunctionality along with long-term durability to drive both HER and OER with overpotentials of 78 and 175 mV. Also, an assembled water-splitting system revealed a low cell voltage of 1.48 V. Thus, this work provides significant insight to significantly and synchronously enhance surface utilization of MXene with abundant electrochemical active sites, crucial for designing high-performance water-splitting electrolyzer. [ABSTRACT FROM AUTHOR]

Due to the wide bandgap width, the lack of oxidation capacity, high carrier recombination rate and limited solar absorption seriously inhibit the photocatalytic activity of pure AlN. Using first principles, we report an efficient method, nonmetal-nonmetal (C–F and B–O) passivation co-doping and H interstitial synergistic biaxial stress action, to solve all the above problems in AlN. We found that by applying appropriate tensile strain, Al 36 N 34 C N1 F N3 H and Al 36 N 34 B N1 O N3 H doped structures can reduce the band gap and make the UV absorption edge redshift. The electron and hole can be separated quickly, and Al 36 N 34 C N1 F N3 H has better photocatalytic activity. It can also raise the potential of CBM and VBM to generate hydrogen and oxygen spontaneously and is beneficial to broadening the absorption range of sunlight. Through the theoretical evaluation of HER and OER activities of Al 36 N 34 C N1 F N3 H, we found that Al 36 N 34 C N1 F N3 H is suitable to be a good catalyst for the photocatalytic reaction. Our results are helpful for the design of high-efficiency sunlight responsive AlN photocatalysts for solar water splitting. [Display omitted] • Accelerate the separation of electron and hole. • Reduce band gap and UV absorption edge redshift. • Raise the potential of CBM and VBM to generate hydrogen and oxygen spontaneously. [ABSTRACT FROM AUTHOR]

Hydrogen production by photoelectrochemical (PEC) water splitting has been extensively studied on copper indium sulfide (CuInS2, CIS) photoelectrodes. In the hydrogen evolution reaction (HER), nickel species were investigated as an alternative cocatalyst to platinum from the viewpoint of elemental strategy: Ni cocatalyst was deposited on In2S3-supported CIS by cyclic voltammetry (CV) and chronoamperometry (CA). The Ni–In2S3/CIS photoelectrode consisted of metallic Ni covered with Ni(OH)2 as a passivation layer. Furthermore, the particle size of Ni species could be changed by the degree of reduction and oxidation reaction, suppressing particle size increase. The Ni–In2S3/CIS photoelectrode fabricated by the CV exhibited higher PEC performance than that by the CA at a constant potential. These results clearly show that CV is an effective method for depositing relatively uniform and small Ni particles, which strongly affects the efficiency of PEC water splitting. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting in a pH-neutral electrolyte has attracted more and more attention in the field of sustainable energy. Bismuth vanadate (BiVO4) is a highly promising photoanode material for PEC water splitting. Additionally, cobaltous phosphate (CoPi) is a material that can be synthesized from Earth's rich materials and operates stably in pH-neutral conditions. Herein, we propose a strategy to enhance the charge transport ability and improve PEC performance by electrodepositing the in situ synthesis of a CoPi layer on the BiVO4. With the CoPi co-catalyst, the water oxidation reaction can be accelerated and charge recombination centers are effectively passivated on BiVO4. The BiVO4/CoPi photoanode shows a significantly enhanced photocurrent density (Jph) and applied bias photon-to-current efficiency (ABPE), which are 1.8 and 3.2 times higher than those of a single BiVO4 layer, respectively. Finally, the FTO/BiVO4/CoPi photoanode displays a photocurrent density of 1.39 mA cm−2 at 1.23 VRHE, an onset potential (Von) of 0.30 VRHE, and an ABPE of 0.45%, paving a potential path for future hydrogen evolution by solar-driven water splitting. [ABSTRACT FROM AUTHOR]

Organic semiconductor-based photoelectrodes are gaining significant attention in photoelectrochemical (PEC) value-added chemical production systems, which are promising architectures for solar energy harvesting. Organic semiconductors consisting of conjugated carbon–carbon bonds provide several advantages for PEC cells, including improved charge transfer, tunable band positions and band gaps, low cost, and facile fabrication using organic solvents. This review gives an overview of the recent advances in emerging single organic semiconductor-based photoelectrodes for PEC water splitting and the various strategies for enhancing their performance and stability. It highlights the importance of photoelectrodes based on donor–acceptor bulk heterojunction (BHJ) systems for fabricating efficient organic semiconductor-based solar energy-harvesting devices. Furthermore, it evaluates the recent progress in BHJ organic base photoelectrodes for producing highly efficient PEC value-added chemicals, such as hydrogen and hydrogen peroxide. Finally, this review highlights the potential of organic-based photoelectrodes for bias-free solar-to-chemical production, which is the ultimate goal of PEC systems and a step toward achieving reliable commercial technology. [ABSTRACT FROM AUTHOR]

The limited performance of BiVO4 for photoelectrochemical (PEC) water splitting is currently restricted to limited light absorption and rapid carrier recombination. Herein, molecular copper phthalocyanine (CuPc) and FeOOH co‐integrated BiVO4 photoanode are prepared by a simple dipping method and demonstrate significantly improved PEC water oxidation activities. The optimized BiVO4/CuPc/FeOOH photoanode attains a photocurrent density of 3.67 mA cm−2 at 1.23 VRHE and maintains the PEC performance without significant decay over a long period of time. In addition, significant increase of charge separation efficiency and decrease of charge transfer resistance of the BiVO4/CuPc/FeOOH photoanode also demonstrate that the hole–electron transfer and water oxidation reaction are promoted. It is found that CuPc has a similar structure to photosensitized chlorophyll, which can broaden the absorption range of BiVO4 in the visible region and improve the photo‐generated carriers transfer in the semiconductor. Whereas the FeOOH layer can rapidly transfer the photo‐generated holes into the electrolyte to participate in the water oxidation reaction as oxygen evolution cocatalyst. This work provides a feasible pathway to improve the PEC water splitting performance of BiVO4 by increasing light absorption and accelerating carrier transfer. [ABSTRACT FROM AUTHOR]

Construction of Z -scheme graphitic carbon nitride-titanium dioxide nanotubes (C 3 N 4 -TNT) has been known useful to optimize the band structure for improving photon capture and for accelerating charge carrier separation and transfer rate in photoelectrochemical water splitting (PECWS) cells. However, the reported operating potential window in a PECWS cell, often in 0 – 1.23 V RHE (volt versus reversible hydrogen electrode) plus its overpotential, is too narrow to understand the C 3 N 4 -TNT electrode. Herein, a broad potential window of −0.5 − 2.5 V RHE is applied to C 3 N 4 -TNT@Ti and recorded via the polarization test under chopped sunlight to analyze the effect of both electrons from external electrical circuit and photons from simulated sunlight. In 0 – 2.5 V RHE , the potential enhances the photocurrent density. For example, at 1.6 V RHE , the C 3 N 4 -TNT sample exhibits 1.8-time higher photocurrent density than that of pure TNT. In −0.5 − 0 V RHE , i.e., both samples do not give photo-current response. In addition, for advanced water oxidation/reduction beyond WS to oxygen/hydrogen, a large potential window will be expected. Further, the light capture ability, the charge carrier recombination rate, and the electron flow path through the C 3 N 4 -TNT junction without and with reverse/forward potentials are discussed to elucidate the effect of the applied potential. [Display omitted] • Z scheme graphitic carbon nitride-anodic TiO 2 nanotubes (C 3 N 4 -TNT) is prepared. • Polarization curve of C 3 N 4 -TNT is recorded in a broad potential, −0.5 − 2.5 V RHE. • C 3 N 4 -TNT shows enhanced light absorption and promoted charge carrier separation. • The effect of potential and solar light on C 3 N 4 -TNT is investigated. • The effect of reverse and forward potential on C 3 N 4 -TNT is discussed. [ABSTRACT FROM AUTHOR]

Using silicon in multijunction photocells leads to promising device structures for direct photoelectrochemical water splitting. In this regard, photoelectron spectra of silicon surfaces are used to investigate the energetic condition of contact formation. It is shown that the Fermi‐level position at the surface differs from the values expected from their bulk doping concentrations, indicating significant surface band bending which may limit the overall device efficiency. In this study, the influence of different surface preparation procedures for p‐ and n‐doped Si wafers on surface band bending is investigated. With the help of photoemission and X‐ray absorption spectroscopy, Si dangling bonds are identified as dominating defect centers at Si surfaces. These defects lead to an occupied defect band in the lower half and an unoccupied defect band in the upper half of the Si bandgap. However, partial oxidation of the defect centers causes a shift of defect bands, with only donor states remaining in the Si bandgap. Source‐induced photovoltages at cryogenic temperatures indicate that partial surface oxidation also decreases the recombination activity of these defect centers. It is shown that defect distribution, defect concentration, and source‐induced photovoltages need to be considered when analyzing Fermi‐level pinning at Si surfaces. [ABSTRACT FROM AUTHOR]

Surface engineering has outstanding advantages for improving the carrier exaction of photoelectrodes in the photoelectrochemical water splitting field. NiFe‐layered double hydroxides (NiFe‐LDH), as promising catalysts for water oxidation, can facilitate carrier transport. But surface collapse and structural deformation limit their applications. In this work, a hematite (α‐Fe2O3) photoanode is sequentially cumulatively modified with NiFe‐LDH (Ni3FeOOH), Ag/SiO2, and FeOOH, and exhibits a high photocurrent density, which increases from 0.92 to 4.54 mA cm−2 at 1.23 V relative to the standard hydrogen electrode (VRHE). The mechanism studies demonstrate that the introduction of FeOOH suppresses the electrochemical self‐reduction of Ni3FeOOH, remedies the obvious valley formed in the current density and voltage curve, reduces recombination, and facilitates the OH− transformation, which increases the catalytic activities of the photoanode. The Ag@SiO2 nanoparticles can reduce the interface defects between Ni3FeOOH and FeOOH. The density‐functional theory calculation reveals that the valley is caused by the direction of the internal electric field formed between Ni3FeOOH and α‐Fe2O3, which is opposite to that of solid–liquid junction, resulting in serious carrier recombination. FeOOH possesses a higher electrostatic potential than that of Ni3FeOOH and α‐Fe2O3 and forms an internal electric field directing from α‐Fe2O3/Ni3FeOOH to FeOOH, which synergistically promotes carrier separation with solid–liquid junction. [ABSTRACT FROM AUTHOR]

The direct laser synthesis of periodically nanostructured 2D transition metal dichalcogenide (2D-TMD) films, from single source precursors, is presented here. Laser synthesis of MoS2 and WS2 tracks is achieved by localized thermal dissociation of Mo and W thiosalts, caused by the strong absorption of continuous wave (c.w.) visible laser radiation by the precursor film. Moreover, within a range of irradiation conditions we have observed occurrence of 1D and 2D spontaneous periodic modulation in the thickness of the laser-synthesized TMD films, which in some cases is so extreme that it results in the formation of isolated nanoribbons with a width of ~200 nm and a length of several micrometers. The formation of these nanostructures is attributed to the effect that is known as laser-induced periodic surface structures (LIPSS), which is caused by self-organized modulation of the incident laser intensity distribution due to optical feedback from surface roughness. We have fabricated two terminal photoconductive detectors based on nanostructured and continuous films and we show that the nanostructured TMD films exhibit enhanced photo-response, with photocurrent yield increased by three orders of magnitude as compared to their continuous counterparts. [ABSTRACT FROM AUTHOR]

Solar‐driven water electrolysis has been considered to be a promising route to produce green hydrogen, because the conventional water electrolysis system is not completely renewable as it requires power from nonrenewable fossil fuel sources. This review emphasizes the strategies for solar‐driven water electrolysis, including the construction of photovoltaic (PV)‐water electrolyzer systems, PV‐rechargeable energy storage device‐water electrolyzer systems with solar energy as the sole input energy, and photoelectrochemical water splitting systems. The basic discussions of the above strategies for solar‐driven water electrolysis are first presented. Meanwhile, replacing the oxygen evolution reaction with the electrooxidation of organic compounds can effectively improve the efficiency of water splitting. Also, solar‐driven seawater electrolysis greatly broadens the practical applications due to the abundant reserves of seawater. Recent years have witnessed great development in the field of solar‐driven water electrolysis. The recent research development in the area is subsequently reviewed. Finally, perspectives on the existing challenges along with some opportunities for the further development of solar‐driven water electrolysis are provided. [ABSTRACT FROM AUTHOR]

Developing an efficient photoanode to convert solar energy into hydrogen fuel confronts big challenges owing to the sluggish water oxidation kinetics. Herein, we proposed a feasible method to coat Co-based metal-organic framework (Co-MOF) on Ti doped α-Fe 2 O 3 and revealed its functions on the oxygen evolution reaction (OER) and photoelectrochemical (PEC) water oxidation. The Co-MOF/Ti–Fe 2 O 3 showed a photocurrent density of 1.01 mA/cm2 (1.23V RHE) with a low turn-on voltage (V on) of 0.80 V RHE. The significant improvement of photocurrent density which was ca. 3 times higher than the pristine Fe 2 O 3 , was contributed by the improved charge separation efficiency on the surface rather than in the bulk. And this was validated by the increased trapping capacitance (C trap) and reduced charge transport resistance (R ct). Additionally, the low V on was attributable to the compromise of introduced surface states and the catalytic effect of the Co-MOF. In this work, we discovered the Co-MOF not only offered catalysis sites for OER, but shed light on its influence on the overall PEC water oxidation, and led to an in-depth understanding of cocatalysts on the PEC water splitting. • Co-MOF coated Ti-oped Fe 2 O 3 is successfully prepared by a facile two-step method. • Photocurrent density significantly increases by 3 times and reaches 1.01 mA/cm2. • Co-MOF shows excellent oxygen evolution kinetics. • The Co-MOF would introduce the new surface states and lower the photovoltage. • Co-MOF has little effect or deteriorates the charge separation efficiency in bulk. [ABSTRACT FROM AUTHOR]

Green hydrogen is set to become the energy carrier of the future, provided that production technologies such as electrolysis and solar water splitting can be scaled to global dimensions. Testing these hydrogen technologies on the MW scale requires the development of dedicated new test facilities for which there is no precedent. This perspective highlights the challenges to be met on the path to implementing a test facility for large-scale water electrolysis, photoelectrochemical and photocatalytic water splitting and aims to serve as a much-needed blueprint for future test facilities based on the authors' own experience in establishing the Hydrogen Lab Leuna. Key aspects to be considered are the electricity and utility requirements of the devices under testing, the analysis of the produced H2 and O2 and the safety regulations for handling large quantities of H2. Choosing the right location is crucial not only for meeting these device requirements, but also for improving financial viability through supplying affordable electricity and providing a remunerated H2 sink to offset the testing costs. Due to their lower TRL and requirement for a light source, large-scale photocatalysis and photoelectrochemistry testing are less developed and the requirements are currently less predictable. [ABSTRACT FROM AUTHOR]

Highly ordered TiO2 nanotube (NT) arrays grown on Ti mesh and Ti foil were successfully prepared by a controlled anodic oxidation process and tested for water photo-electrolysis. Electrochemical impedance spectroscopy (EIS), combined with other electrochemical techniques (cyclic voltammetry and chronoamperometry) in tests performed in the dark and under illumination conditions, was used to correlate the photoactivity to the specific charge transfer resistances associated with a 3D (mesh) or 2D (foil) geometry of the support. The peculiar structure of the nanotubes in the mesh (with better light absorption and faster electron transport along the nanotubes) strongly impacts the catalytic performances under illumination. H2 production and current density in water photo-electrolysis were over three times higher with the TiO2NTs/Ti mesh, compared to the foil in the same conditions. The results obtained by the EIS technique, used here for the first time to directly compare TiO2 nanotubes on two different supports (Ti foil and Ti mesh), led to a better understanding of the electronic properties of TiO2 nanotubes and the effect of a specific support on its photocatalytic properties. [ABSTRACT FROM AUTHOR]

Photoelectrochemical water splitting is a promising approach to produce green hydrogen using solar energy. A primary bottleneck remains the lack of efficient photoanodes to catalyze the sluggish water photooxidation reaction. Engineering photoabsorbers with a narrow bandgap and suitable band edge can boost the photoelectrochemical performance. Herein, nanostructured iron tungstate (FeWO4) photoanodes are engineered directly on a fluorine doped tin oxide glass substrate via a scalable and ultra-fast flame synthesis route in 13 seconds. Physiochemical, optoelectronic, and electrochemical properties of these photoanodes are systematically investigated. The key roles of charge transport, transfer, and dissolution of W and Fe ions from the FeWO4 matrix within long-term performance are revealed. Optimal FeWO4 photoanode with a bandgap of 1.82 eV and a FeOOH/NiOOH co-catalyst coating shows an improved water photooxidation performance, reaching a photocurrent density of 0.23 mA cm-2 at 1.4 V versus reversible hydrogen electrode in 1 m potassium hydroxide. It further demonstrates relatively good photostability, maintaining ≈96% of photocurrent density after 1-hour continuous photooxidation, albeit some trace of Fe, W and Ni elements dissolution. Insights on the photooxidation performance of nanostructured FeWO4 provide promising directions for the engineering of small band-gap catalysts for a variety of photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

Epoxides are significant intermediates for the manufacture of pharmaceuticals and epoxy resins. In this study, we develop a Br−/BrO− mediated photoelectrochemical epoxidation system on α-Fe2O3. High selectivity (up to >99%) and faradaic efficiency (up to 82 ± 4%) for the epoxidation of a wide range of alkenes are achieved, with water as oxygen source, which are far beyond the most reported electrochemical and photoelectrochemical epoxidation performances. Further, we can verify that the epoxidation reaction is mediated by Br−/BrO− route, in which Br− is oxidized non-radically to BrO− by an oxygen atom transfer pathway on α-Fe2O3, and the formed BrO− in turn transfers its oxygen atom to the alkenes. The non-radical mediated characteristic and the favorable thermodynamics of the oxygen atom transfer process make the epoxidation reactions very efficient. We believe that this photoelectrochemical Br−/BrO−-mediated epoxidation provides a promising strategy for value-added production of epoxides and hydrogen. Alkene epoxidation, whose products are important intermediates for the manufacture of pharmaceuticals and epoxy resins, has attracted extensive attention. Unlike the conventional electrochemical Br−/Br2-mediated epoxidation, here the authors report a photoelectrochemical Br−/BrO−- mediated system to achieve efficient epoxidation performance on α-Fe2O3. [ABSTRACT FROM AUTHOR]