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The increasing adoption of solar energy as a renewable power source marks a significant shift toward clean, sustainable alternatives to conventional energy forms. A notable development in this field is the advancement of thin monocrystalline silicon (c‐Si) solar cells. Characterized by their lightweight, flexible nature, these solar cells promise to transform the renewable energy landscape with enhanced durability, adaptability, and portability. Amidst the growing demand for sustainable energy solutions, refining and evolving thin c‐Si solar cell technologies is crucial. This review comprehensively examines the latest progress in thin c‐Si solar energy conversion device technologies, offering an extensive overview of current methodologies for producing thin c‐Si films, advanced light trapping techniques, surface passivation strategies, and methods for managing thin wafers. It also explores the wide‐ranging applications of thin c‐Si solar cells. Furthermore, this article sheds light on the techno‐economic aspects, highlighting the intertwined challenges of commercializing these innovative cells. Through an in‐depth analysis of the latest advancements, this review serves as a valuable resource for researchers and industry experts, keeping them abreast of current trends and catalyzing further advancements in thin c‐Si solar cell technology. [ABSTRACT FROM AUTHOR]

Copper indium sulfide quantum dots (CIS QDs) possess the desired optical properties to act as photoanodic material in photoelectrochemical cells, like a high molar absorption coefficient over the entire visible spectrum and long exciton lifetimes. The already reported procedures that utilize photoanodes based on such nanoparticles, however, exploit harsh conditions or utilize non‐scalable, expensive, and low‐yield syntheses. Here, the construction of CIS QDs adsorbed onto TiO2/FTO photoanodes (FTO = fluorine‐doped tin oxide) with a process aimed at avoiding these issues is proposed. In particular, the employment of dihydrolipoic acid as the ligand allows an easy and cost‐effective functionalization. CdS layers are deposited onto the nanoparticles to enhance the photoelectrochemical properties. Full characterization of the steady–state and transient photoelectrochemical properties of the electrodes is performed to gain information on the interfacial dynamics among the different components of the electrode. Maximum IPCEs of the order of 50% and a spectral sensitization extended up to 700 nm are obtained in the optimized conditions. [ABSTRACT FROM AUTHOR]

Density‐functional theory (DFT) is pivotal in the advancement of photocatalysis and photoelectrocatalysis. Its capability to explore electronic structures of materials contributes significantly to clarifying the mechanisms of photocatalytic (PC) and photoelectrocatalytic (PEC) processes. DFT calculations enable a deeper understanding of how these processes work at a molecular level, which is essential for designing versatile photocatalysts and photoelectrodes and optimizing reaction pathways. In this perspective, key PC and PEC applications, such as H2 production, CO2 reduction, dye degradation, and N2 reduction, where DFT is instrumental in optimizing materials designs and reaction pathways, are highlighted. Exploration on the synergy between experimental research and DFT calculations is highlighted, which is crucial for the development of efficient and environmentally friendly energy solutions. The discussion further extends to challenges and future directions, emphasizing the need for incorporating factors, including discrepancy in scale, light illumination, electrolyte presence, and applied bias, into DFT calculations, to achieve a more comprehensive understanding of PC and PEC systems. In this perspective, it is aimed to provide a holistic view of the current state and potential advancements in photocatalyst and photoelectrode modeling, thereby guiding future research toward more effective and sustainable energy and chemical production processes in PC and PEC systems. [ABSTRACT FROM AUTHOR]

The growing demand for alternative energy sources has driven significant developments in novel device designs that generate energy through light conversion. Among the different types of solar cells, dye-sensitized solar cells (DSSCs) have emerged as one of the most promising options due to their potential to approach theoretical efficiencies of up to 46%. Although current real-world efficiencies typically range from 10 to 14% that generates numerous opportunity areas for DSSC improvement through different strategies, including the development of innovative solar cell structures, new growth or synthesis processes, and the integration of novel oxide materials. Titanium dioxide is one of the most significant oxide semiconductors and its interest has notably increased in recent years due to its unique optoelectronic properties and its applications in dye-sensitized solar cells (DSSCs). In DSSCs, photoelectrodes play a vital role in photoconversion. Photoelectrodes for DSSCs require blocking and porous oxide semiconductor layers to prevent electron leakage and enhance efficiency. Typically, these layers are produced through various techniques and steps, complicating the fabrication process and extending processing times. Therefore, in this work, we propose a one-step method to simultaneously grow TiO2-blocking and porous layers for DSSC photoelectrodes at relatively low temperatures. Characterization results using FESEM/EDS, XRD, and UV–visible spectroscopy confirm the growth of both compact and porous layers. These layers are composed of the anatase particulate deposits (100–200 nm) with acceptable grain sizes (17.3–84.1 nm) and exhibit a suitable band gap (3.14 eV). Finally, TiO2 films were applied in DSSCs as photoelectrodes and showed promising performance in solar cell prototypes. [ABSTRACT FROM AUTHOR]

CdS nanospheres were grown on indium tin oxide (ITO) substrate using a hydrothermal method. The crystal structure, morphology and electronic structure of the samples synthesized were characterized in detail. The results confirm that the crystallinity, size, crystal defects of the CdS nanospheres and the film thickness of CdS photoelectrodes can be tuned by varying the precursor Cd2+ concentration. Combined with charge transfer dynamics analysis, it can be found that proper particle size and film thickness, as well as fewer defects, will result in better charge separation efficiency of the prepared CdS/ITO photoelectrodes, thereby exhibiting better photoelectrochemical performance for water splitting. The optimized CdS/ITO photoelectrode synthesized with a Cd2+ concentration of 0.14 mol·L−1 gave a photocurrent density of 5.10 mA·cm−2 at potential of 1.23 V versus the reversible hydrogen electrode (RHE), under a simulated solar illumination of 100 mW·cm−2.

The exceptional optical properties and good temperature stability of inorganic halide perovskites make them appealing materials for photoelectrochemical water splitting. However, their instability towards water molecules is a serious challenge. Our solution to this issue is to use waste carbon-based toner from cartridge printers to protect CsPbBr 3 -based photoanodes in aqueous electrolytes in an environmentally friendly, cost-effective, and efficient way. Waste carbon toner: graphite (WCTG) protective layer is a novel approach that we present here to recycle these environmentally harmful pollutants. Through adjustment of WCTG ratios, we discovered that the CsPbBr 3 photoanodes' photocurrent densities for water oxidation achieved 3.6 and 4.6 mA cm−2 at 1.23 vs reversible hydrogen electrode at pH 7 and pH 12, respectively. After 5 h, the most stable electrodes still maintained their photocurrent density, a critical step towards the circular economy of waste toners and the use of inorganic halide perovskites for solar water splitting. [Display omitted] • The photoanode device is prepared using the CsPbBr 3 perovskite structure as a light absorber. • Waste carbon-based toner was used on CsPbBr 3 perovskite photoanodes as a protective layer against water molecules. • The PEC water oxidation performance of the CsPbBr 3 photoanodes strikingly improves with increasing graphite. • Increasing the amount of waste carbon-based toner increases the stability of CsPbBr 3 photoanodes in aqueous electrolytes. [ABSTRACT FROM AUTHOR]

Nanoparticles and nanocomposites prepared by the hydrothermal method (ZnO, ZnO/MnO2) were used to build dye-sensitized solar cells (DSSCs), which were used as photoelectrodes using two natural dyes as the absorbent media: red (Hibiscus sabdariffa) and green (Apium graveolens). The results showed the efficiency of the green dye in DSSCs is superior to the red dye in terms of conversion efficiency (η). The purpose of the study is to improve the performance of dye solar cells. The properties of nanomaterials were studied by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) for the analysis of ZnO NPs and ZnO/MnO2, whereas the sizes of the prepared materials are within the size of 1–100 nm. The solar cell parameters were obtained from simple (I-V) measurements for nanomaterials prepared using two-dye DSSCs where Isc represents the short circuit current through the solar cell when the voltage across the solar cell is zero, and Voc represents the open circuit voltage across the solar cell and is the maximum voltage available from the solar cell. The photoelectrochemical properties of the two dye DSSCs in this study were calculated at 22.53 mW/cm2 of the light intensity.

A BaTaO2N (BTON) particulate photocatalyst enables solar water splitting in response to visible light irradiation at wavelengths of up to 640 nm. The specific nitridation conditions produced distinct types of BTON particles with the capability of one‐step overall water splitting (Active‐BTON) and without the overall water splitting activity (Inactive‐BTON). Unveiling the intrinsic differences between the active‐ and inactive‐BTON particles is crucial for obtaining more in‐depth information about the water splitting activity. Herein, we investigated the electrochemical (EC) and photoelectrochemical (PEC) properties of these BTON photocatalysts using the particulate‐based photoelectrodes for water splitting. EC measurements, including Mott–Schottky analysis, revealed that the flat band potential of Active‐BTON is located at a potential that is more positive than that of Inactive‐BTON, whereas the carrier concentration of Active‐BTON is one‐tenth lower than that of Inactive‐BTON. Irrespective of the pH value of the 1.0 M potassium phosphate aqueous solution, the Active‐BTON‐based photoelectrodes showed a higher photocurrent than that of Inactive‐BTON under simulated AM 1.5G solar illumination. The PEC performance of the BTON was found to be limited by the electrocatalytic activity of the CoOx co‐catalyst, specifically the electrolyte pH. [ABSTRACT FROM AUTHOR]

The world is facing significant energy challenges, and renewable hydrogen production has emerged as a promising solution. Water splitting by photoelectrochemical cells (PEC) is one of the popular methods used for hydrogen production. For this process, hematite (α − Fe2O3) is emerging as a suitable candidate (as photoanodes) because of its relative abundance, stability and wide bandgap ranging from 1.9 to 2.2 eV that is suitable for solar absorption. This review provides a critical analysis about the performance, comprehension, and applications of α − Fe2O3 as a photoanode for water splitting. Over the years, there has been a concerted effort to enhance the performance of α − Fe2O3 photoanodes. It resulted in various strategies being developed to synthesize and modify the photoanode, resulting in significant advancements. The primary focus is given to designing of a nanostructure, that is doped with suitable elements, modified with the help of co-catalysts and heterostructure formation.

This research introduces a pioneering approach to solar water splitting technology, utilizing an innovative, highly efficient immersed system. The system incorporates a flexible array of electrochemical and photoelectrochemical cells, powered by high‐performance III‐V triple‐junction cells. Remarkably, this method significantly boosts the solar‐to‐hydrogen (STH) conversion efficiency, reaching a record 20.7% under 1 sun illumination, employing earth‐abundant catalysts operating at ambient temperature. These findings highlight extensive scope for further optimization, including minimizing optical transmission losses, mitigating shading effects, and reducing the overpotential of the electrochemical cells, thereby augmenting the STH efficiency to an estimated 28%. Through a comprehensive techno‐economic analysis, a levelized cost of hydrogen (LCOH) of 8.3 USD kg−1 is estimated, forecasting the potential for a reduction to a competitive 1.8 USD kg−1 with improved efficiency, increased capacity factors, and decreased production costs. A sensitivity analysis emphasizes the significant influence of factors such as III‐V cell cost, electrolyzer membrane cost and capacity factor on the LCOH. Overall, this study signifies crucial progress toward a highly efficient and economically viable solar water splitting solution, promising a sustainable route for hydrogen production. [ABSTRACT FROM AUTHOR]

Underwater optical communication (UOC) has attracted considerable interest in the continuous expansion of human activities in marine/ocean environments. The water‐durable and self‐powered photoelectrodes that act as a battery‐free light receiver in UOC are particularly crucial, as they may directly face complex underwater conditions. Emerging photoelectrochemical (PEC)‐type photodetectors are appealing owing to their intrinsic aqueous operation characteristics with versatile tunability of photoresponses. Herein, a self‐powered PEC photodetector employing n‐type gallium nitride (GaN) nanowires as a photoelectrode, which is decorated with an iridium oxide (IrOx) layer to optimize charge transfer dynamics at the GaN/electrolyte interface, is reported. Strikingly, the constructed n‐GaN/IrOx photoelectrode breaks the responsivity‐bandwidth trade‐off limit by simultaneously improving the response speed and responsivity, delivering an ultrafast response speed with response/recovery times of only 2 µs/4 µs while achieving a high responsivity of 110.1 mA W−1. Importantly, the device exhibits a large bandwidth with 3 dB cutoff frequency exceeding 100 kHz in UOC tests, which is one of the highest values among self‐powered photodetectors employed in optical communication system. [ABSTRACT FROM AUTHOR]

Photoresponsive batteries are an innovative technology that combines conversion and storage of solar energy, providing a potential solution for large‐scale utilization of solar energy while reducing the reliance on traditional energy storage devices to meet the growing demand for energy. In search of more resource‐saving alternatives to lithium‐ion batteries, researchers are turning to zinc, which is abundant and environmentally friendly due to its recyclability. Zinc batteries offer high energy density and aqueous stability, making them a popular choice among researchers. This review summarizes the recent progress in photoresponsive zinc‐based batteries. First, the photoresponsive zinc‐based batteries are categorized into two groups: photoresponsive zinc‐ion batteries and photoresponsive zinc–air batteries. The discussion then focuses on various photoelectrode designs, including some interesting strategies. Finally, the technical challenges associated with photoresponsive zinc‐based batteries are summarized and discussed, and future research directions are proposed. [ABSTRACT FROM AUTHOR]

Recent studies have shown that p‐type polymeric semiconductors enable a new type of wireless, optically triggered interface with cells and tissues. Poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) has already been used to create such optobioelectronic interfaces, producing reactive oxygen species and hydrogen peroxide that act as messengers in biological systems to impact cell signaling and proliferation. However, the use of P3HT in biomedical in‐vivo applications is limited as its optical absorption does not match the tissue transparency window. This paper compares the performance of P3HT with two low band‐gap polymers commonly employed in high‐performance organic solar cells, namely Poly[[4,8‐bis[5‐(2‐ethylhexyl)‐2‐thienyl]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl]‐2,5‐thiophenediyl[5,7‐bis(2‐ethylhexyl)‐4,8‐dioxo‐4H,8H‐benzo[1,2‐c:4,5‐c′]dithiophene‐1,3‐diyl]] (PBDB‐T) and Poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b] thiophenediyl}) (PTB7). Their photogeneration capabilities are quantified in physiological‐like conditions through photocurrent analysis and a hydrogen peroxide assay, finding a superior photocurrent generation and a better H2O2 photogeneration yield in PTB7 as compared to the other two polymers. Spectroscopic and structural investigations are used to compare such differences by comparing their energy levels at the electrochemical interface and their morphologies. Finally, biocompatibility is tested both in dark and illuminated conditions and effective in‐vitro intracellular ROS production is demonstrated. These findings provide insight into the physico‐chemical properties crucial for the development of novel, less invasive, optically operated bioelectronic interfaces. [ABSTRACT FROM AUTHOR]

Photoresponsive batteries are an innovative technology that combines conversion and storage of solar energy, providing a potential solution for large‐scale utilization of solar energy while reducing the reliance on traditional energy storage devices to meet the growing demand for energy. In search of more resource‐saving alternatives to lithium‐ion batteries, researchers are turning to zinc, which is abundant and environmentally friendly due to its recyclability. Zinc batteries offer high energy density and aqueous stability, making them a popular choice among researchers. This review summarizes the recent progress in photoresponsive zinc‐based batteries. First, the photoresponsive zinc‐based batteries are categorized into two groups: photoresponsive zinc‐ion batteries and photoresponsive zinc–air batteries. The discussion then focuses on various photoelectrode designs, including some interesting strategies. Finally, the technical challenges associated with photoresponsive zinc‐based batteries are summarized and discussed, and future research directions are proposed.

This study deals with the nanoarchitectonic concept applied to the design of photoelectrodes built on two types of cluster core building blocks, namely, {Re6Si8} and {Re6Sei8}. The effect of the nature of the metal/ligand on photoinduced conductivity properties is thus investigated through an in‐depth photoelectrochemical study and it is rationalized by the establishment of an energy diagram using a set of complementary optical (ultraviolet–vis–near infrared), electrochemical and spectroscopic (X‐ray photoelectron spectroscopy) characterization techniques. The optical and electronic properties of {Re6Qi8}‐based films (Q = S or Se) are drastically dependent on the composition. The sulfide‐based photoelectrodes exhibit ambipolar behavior with an n‐type domination whereas the selenide‐based photoelectrodes have a p‐type semiconducting behavior. Such electronic properties can be exalted by increasing the interactions between the cluster building blocks by heating. The design of mixed {Re6Qi8}‐based photoelectrodes combining the two n‐{Re6Si8} and p‐{Re6Sei8} cluster core‐based building blocks is explored. The physical properties of the heterostructures can be tuned by controlling the {Re6Si8}:{Re6Sei8} ratio and the interaction between the clusters. The creation of such nanoarchitectonic p–n junctions allows the optimization of the photocurrents generated by increasing the separated charge state lifetime that turns out to be attractive for solar cell applications. [ABSTRACT FROM AUTHOR]

The increasing knowledge in nanoscience and materials technology promoted the development of advanced materials with enhanced and unusual properties suitable for sustainable applications ranging from energy to environmental purposes. Here are presented some results from our current investigations on composite semiconducting materials. The investigated composites have been prepared from different nitrogen precursors and thin films of TiO2 nanotubes. The synergy between hetero-structures based on graphitic-C3N4 and thin films of titania nanotubes obtained by anodisation was studied. The composites have been characterised with several complementary techniques to evidence the relation between photo-behaviour and the composition of the samples. This study allows new insights into the nature of the specific enhanced properties due to this synergy among the two compounds. The g-C3N4/TiNT heterojunctions showed enhanced photo-electrochemical properties observed from the photocurrent measurements. The as-prepared composites have been investigated as cathode materials in the electrocatalytic reduction of oxalic acid (OX), evidencing the capability of tuning the reaction toward glycolic acid with respect to the pristine TiNT array. The observed Faradic efficiency (FE) for the composites follows the trend: TiNT-U6 > TiNT-M6 > TiNT-MU18. TiNT-U6 shows the best performances (FEGC = 63.7%; FEGO = 15.5%; OX conversion = 61. 4%) after 2 h of reaction. The improved photo-electrochemical properties make these materials suitable for H2 production, solar-light-driven water splitting, and CO2 reduction applications. [ABSTRACT FROM AUTHOR]

This work reports on the preparation of Cr-doped TiO2 (Cr–TiO2), Cu-doped (Cu-TiO2), and its utilization in the photoanode of a solar redox flow battery (SRFB). A pure TiO2 electrode, Cr-doped TiO2 electrode, and Cu-doped TiO2 electrode coated with different layers are prepared by the sol-gel method. XRD, XPS, and SEM are used to characterize the relevant data of the electrode. All three electrodes show the structure of the anatase phase, but the Cu-TiO2 and Cr-TiO2 electrodes are more crystalline. Using these materials as photoelectrodes to prepare integrated solar flow cells, the semi-cell and full-cell tests show that the doping of Cr and Cu improves the efficiency and charging current of solar cells. The average charging currents of the Cu-TiO2 and Cr-TiO2 electrodes are 384.20 μ A and 450.75   μ A , respectively, compared with the TiO2 electrode; this increment reaches values of 71.23% and 100.97%. [ABSTRACT FROM AUTHOR]

The efficient charge separation and surface state reactions are significant in enhancing the efficiency of photoelectrochemical hydrogen evolution. Herein, we report a ternary heterostructure consisting of CdS/ZnSe sensitized TiO2 nanorod as a photoanode. The heterojunction photoanode considerably widens the photon absorption spectral range and thereby enhances the photocurrent density up to 2 mA/cm2 at 1.23 V versus RHE which is 10 times higher than pristine TiO2 photoanode. The photoelectrochemical results demonstrate a high photocurrent density of 2 mA/cm2 with a photon‐to‐current conversion efficiency of 1.5 % at a very low applied bias (0.2 V vs RHE). The improved PEC performances of the multidimensional hybrid photoanode could be ascribed to the efficient visible‐light absorption of ZnSe and CdS nanocrystals decorated on the surface of 1D TiO2. The rapid electron‐transfer properties owing to higher carrier density, low carrier transport resistance, and an extended lifetime of photoexcited carriers in the multidimensional ZnSe/CdS/TiO2 heterostructure with suppressed surface charge recombination are responsible for enhanced hydrogen evolution activities. [ABSTRACT FROM AUTHOR]

Photoelectrochemical CO2 reduction reaction (PEC CO2RR) is a promising technology which offers the possibility of a carbon‐neutral solar fuel production via artificial photosynthesis. The challenging proton‐coupled multielectron transfers with high energy barriers in CO2RR however pose as a huge hindrance to the technology, which demands strict specifications in the design of photocathode materials so as to improve PEC performances. This review underscores effective design strategies and current material progress for the judicious assembly of photocathode materials for CO2RR. The review begins with elucidating the fundamental principles of CO2 reduction process and photocathode electrochemistry. Based on these, the design criteria and trade‐offs in the design of PEC CO2RR photocathodes are highlighted. The various promotive strategies for photocathodes and their underlying rationales such as doping, defect engineering, nanostructuring, cocatalyst loading, passivation, heterojunction formation, and innovative multijunction configurations are further outlined and design propositions in the area are provided. Following that, various photocathode semiconductor materials categorized into photovoltaic (PV) grade (silicon, III–V semiconductors, chalcogenides) and non‐PV grade (metal oxides) materials are summarized and extensively discussed, along with their recent advances. Finally, perspectives on the design of photocathodes for CO2RR and new paradigms in the field are put forward. [ABSTRACT FROM AUTHOR]

In the global pursuit of sustainable energy, solar-powered resources have received significant attention due to their potential to provide clean and renewable energy. Among these, PEC water splitting stands out as the most effective and environmentally benign technology, with tremendous potential to meet future global demands. However, identifying high-performance, economically viable materials for photoelectrodes which are building blocks of water splitting process, remains a significant challenge. In this regard, transition metal oxide photoanodes such as TiO 2 , WO 3 , BiVO 4 , ZnO, α-Fe 2 O 3 , etc. are potential candidates for efficient water splitting. Nonetheless, intrinsic barriers including limited light harvesting, poor charge separation/transport, and sluggish OER kinetics limit their practical application. To address these issues, zeolitic imidazolate frameworks, a class of unique materials belonging to the metal-organic frameworks family are emerging as a potential catalyst for the development of photoelectrodes owing to their large surface area, extensive redox-active sites, excellent thermal and chemical stability, and hierarchical porosity. This review highlights advancements in employing ZIF-8 and ZIF-67 catalysts to improve the PEC efficiency of established metal oxide semiconducting photoanodes, addressing a gap in the existing literature. For broader context, this review covers PEC water splitting fundamentals and advanced metal oxide/ZIF-based photoelectrode mechanisms, aiding next-generation PEC device design. The conversation about current challenges and future directions will provide new avenues for improving the ZIF-based PEC water splitting landscape. [Display omitted] • This review emphasizes the potential of ZIF-8 and ZIF-67 for enhancing PEC water splitting. • The fundamental redox reactions and PEC water splitting parameters are discussed. • The catalytic features of ZIFs to advance the efficiencies were highlighted. • Recent progress in metal oxide photoanode engineering via ZIFs is presented in-depth. • Current challenges and perspectives for future developments are outlined. [ABSTRACT FROM AUTHOR]

This work shows that ZrO2, used as a modifier of TiO2, can be highly effective as a co-catalyst in the photoelectrocatalytic degradation of dibutyl phthalate (DBP). The monoclinic phase of ZrO2 was easily obtained by chemical deposition on TiO2 nanotubes (Ebg ~3.06 eV), increasing the occurrence of hydroxyl groups and acidity on the surface of the material, as observed by electrophoretic mobility measurements. The optimized photoelectrocatalysis conditions were bias potential of 1.5 V, 0.1 M Na2SO4 (initial pH 6) supporting electrolyte, 6 ppm of DBP, and UV/Vis irradiation. These conditions resulted in complete removal of DBP, down to the limit of detection of the chromatographic method used, with up to complete TOC removal after 60 min of treatment. The effects of pH, bias potential, DBP concentration, and applied potential were investigated. The method was compared with photocatalysis and photolysis. An oxidation mechanism is proposed, based on intermediates detected by LC-MS/MS during 10 min of photoelectrocatalysis. [ABSTRACT FROM AUTHOR]

For photoelectrocatalytic cells, a limitation exists in finding appropriate photoelectrode configurations that couple efficient extraction of high-energy electrons from absorbed photons and selective catalysis. Here we report an organic p-n junction approach to fabricate molecular photoelectrodes for conversion of solar energy and nitrate into valuable ammonia product. Solar irradiation of the photoelectrode generates charge-separated states with electrons and holes spatially separated at the n-type and p-type components, as revealed by surface photovoltage mapping, at a quantum yield of 90%. The high-flux photogenerated electrons are rapidly transferred to the catalyst for solar ammonia production from nitrate reduction at an external quantum efficiency (EQE) and an internal quantum efficiency (IQE) of 57% and 86%, respectively. Time-resolved spectroscopic studies reveal that the large IQE originates from the combined high efficiencies for photoelectron generation, catalyst activation and dark catalysis. In a flow-cell setup coupled with a silicon solar cell, the photoelectrode without bias generates photocurrent of 57 mA cm-2 and ammonia at an EQE of 52%., (© 2024 Wiley‐VCH GmbH.)

Surface engineering of photoelectrodes is considered critical for achieving efficient photoelectrochemical (PEC) cells, and various p-type materials have been investigated for use as photoelectrodes. Among these, the p-type semiconductor/n-type CdS heterojunction is the most successful photocathode structure because of its enhanced onset potential and photocurrent. However, it is determined that the main contributor to the enhanced activity is the Cd-doped layer and not the CdS layer. In this study, a Cd-doped n + p-buried homojunction of a CuInS 2 photocathode is first demonstrated without a CdS layer. The homojunction exhibited a more active and stable PEC performance than the CdS/CuInS 2 heterojunction. Moreover, it is confirmed that Cd doping is effective for other p-type materials. These results strongly suggest that the effects of Cd doping on photocathodes should be carefully investigated when designing CdS/p-semiconductor heterojunction photoelectrodes. They also indicate that the Cd-doped layer has great potential to replace the CdS layer in future photoelectrode designs., (© 2024 Wiley‐VCH GmbH.)

This study offers an in-depth examination of aluminum gallium arsenide (AlGaAs) as a high-performance and durable material for photoelectrochemical water splitting, a key method of cost-effective renewable hydrogen production. Purpose-designed pin-AlGaAs photocathodes are demonstrated to yield a remarkable photocurrent density of over 15 mA/cm 2 and an impressive onset potential of 1.11 V vs RHE. These results significantly outperform those achieved with other materials, marking a considerable advancement in the field. Moreover, this work addresses the long-standing issue of AlGaAs corrosion in an aqueous electrolyte. An innovative approach using a 60 nm TiO 2 protection layer is introduced, providing substantial corrosion resistance in acidic environments and thereby enhancing material durability. This research also provides valuable insights into the role of passivation layers on charge transfer. It was found that an n-GaAs passivation layer further enhances the onset potential, whereas an n-InGaP layer contributes to a decline in the overall performance. These findings pave the way for new applications of AlGaAs in solar water splitting technology, offering a promising pathway toward the development of efficient AlGaAs/Si tandem water splitting devices.

Abstract Highly efficient photoelectrochemical (PEC) water oxidation under solar visible light is crucial for water splitting to produce hydrogen as a source of sustainable energy. Particularly, silver-based nanomaterials are important for PEC performance due to their surface plasmon resonance which can enhance the photoelectrochemical efficiency. However, the PEC of ZnO/Ag2WO4/AgBr with enhanced visible-light water oxidation has not been studied so far. Herein, we present a novel photoelectrodes based on ZnO/Ag2WO4/AgBr nanorods (NRs) for PEC application, which is prepared by the low-temperature chemical growth method and then by successive ionic layer adsorption and reaction (SILAR) method. The synthesized photoelectrodes were investigated by several characterization techniques, emphasizing a successful synthesis of the ZnO/Ag2WO4/AgBr heterostructure NRs with excellent photocatalysis performance compared to pure ZnO NRs photoelectrode. The significantly enhanced PEC was due to improved photogeneration and transportation of electrons in the heterojunction due to the synergistic effect of the heterostructure. This study is significant for basic understanding of the photocatalytic mechanism of the heterojunction which can prompt further development of novel efficient photoelectrochemical-catalytic materials. Graphic Abstract

The photoelectrochemical redox battery (PRB) has been regarded as an alternative candidate for large‐scale solar energy capture, conversion, and storage as it combines the superior advantages of photoelectrochemical devices and redox batteries. As an emerging solar energy utilization technology, significant progress has been made towards promoting and proliferating the practical applications of PRBs. However, wide market penetration of PRBs is still being significantly inhibited by limited photocatalytic activity, low efficiency, among other critical issues. Furthermore, the integration of each component, including solar materials, redox couples, and membranes and their interaction in PRBs play vital roles towards achieving smooth operation and high performance. Herein, the materials, mechanisms, recent advances, and challenges in the use of PRBs are presented. The crucial influence of redox couples, photoelectrode materials, membranes on the performance of the system including how they affect solar energy capture, reaction kinetics, and internal losses are systematically discussed. In addition, the recent advances of a single‐battery of photoelectrode mode and an integrated device of solar cell mode are summarized. Furthermore, the state of the art performance of PRBs and their upscaling progress are also discussed. Finally, the challenges and perspectives for the future development of PRBs are highlighted. [ABSTRACT FROM AUTHOR]

The solar motivated photoelectrochemical (PEC), used in water splitting systems, shows superior talent in converting solar energy in the form of cleaning and in sustaining a chemical energy evolution. PEC systems present by integrating a photoelectrode, which involves light-harvesting to absorb solar energy, thereby introducing an interlayer for the transformation of photogenerated electrons and holes, along with a co-catalyst to trigger oxidation and reduce the chemical reactions. In this review, we describe a variety of two-dimensional (2D) layered photoanodes and photocathodes, such as graphitic carbon nitrides, transition metal dichalcogenides, layered double hydroxides, MXenes, and co-catalysts for the assembly of combined photoelectrodes belonging to oxygen evolution and/or hydrogen evolution chemical reactions. The basic principles of PEC water splitting associated with physicochemical possessions relating to photoelectrodes unified with catalytic chemical reactions have been investigated. Additionally, the mechanisms attributing to a relationship with 2D photoelectrodes have been incorporated as a supplementary discussion. The improvement strategies, which include the construction of heterostructures, surface functionalization, and formations of heterojunctions, have also been discussed. The issues and challenges relevant to the field have been acknowledged for facilitating future research, indicating optimized conversion activity corresponding to PEC water splitting. [ABSTRACT FROM AUTHOR]

Heterojunction engineering enables more versatile and higher performance systems than single components. In parallel with heterojunction engineering, defect engineering has emerged as a means of tailoring the optoelectronic properties of photoelectrodes. However, constructing effective and stable hybrid semiconductor heterojunctions is a challenging task under the strict requirements of band alignment, vacancy characteristics, and interface properties. Herein, the photoelectrochemical (PEC) reduction of CO2 to methanol is augmented by a novel approach explored by modeling the Fermi level in a multi‐interface architecture. The excellent PEC CO2 reduction activity is attributed to the formation of a high‐performance, energetically aligned multi‐interface system of CuO/Cu2O||rGO|h‐WO3|rGO (rGO = reduced graphene oxide layer). The overall performance of this hybrid, system strongly depends on the number of oxygen groups in rGO and the structural properties of rGO. Therefore, to construct an effective PEC system, numerous postsynthetic treatments are explored for their practicality and usefulness. The results reported herein clearly show that the best performance toward the CO2 photoreduction currents of 3 mA/cm2 at 0.00.1 V versus reversable hydrogen electrode (more than double that of the CuO/Cu2O system) has been reached for the semiconductor architecture containing two layers of rGO. [ABSTRACT FROM AUTHOR]

As an eco-friendly, efficient, and low-cost technique, photoelectrochemical water splitting has attracted growing interest in the production of clean and sustainable hydrogen by the conversion of abundant solar energy. In the photoelectrochemical system, the photoelectrode plays a vital role in absorbing the energy of sunlight to trigger the water splitting process and the overall efficiency depends largely on the integration and design of photoelectrochemical devices. In recent years, the optimization of photoelectrodes and photoelectrochemical devices to achieve highly efficient hydrogen production has been extensively investigated. In this paper, a concise review of recent advances in the modification of nanostructured photoelectrodes and the design of photoelectrochemical devices is presented. Meanwhile, the general principles of structural and morphological factors in altering the photoelectrochemical performance of photoelectrodes are discussed. Furthermore, the performance indicators and first principles to describe the behaviors of charge carriers are analyzed, which will be of profound guiding significance to increasing the overall efficiency of the photoelectrochemical water splitting system. Finally, current challenges and prospects for an in-depth understanding of reaction mechanisms using advanced characterization technologies and potential strategies for developing novel photoelectrodes and advanced photoelectrochemical water splitting devices are demonstrated. [ABSTRACT FROM AUTHOR]

Metal oxide materials show promise for application in photoelectrocatalytic conversion due to their inherent advantages involving positive reactive surface, improved light absorption capability, efficient charge separation yield, and fast charge transport channels. The unique electrical and optical properties of metal oxide based photoelectrodes have a great effect on their performance in solar cells, photoelectrocatalysis, and photocatalysis. It has been reported that the presence of defects on grain boundaries, oxygen vacancy, doping strategy, and heterojunction play a vital role in both the efficiency and durability of their photoelectric application. However, the intrinsic mechanisms at the atomic level remained unclear, which require more in‐depth understanding in terms of theoretical analysis. In this Review, we emphatically introduce the recent advances and current challenges of metal oxide‐based photoelectrodes for photoelectrocatalytic application, beneath the structure‐activity relationship of metal oxide catalysts. Then, we give a summary of the state‐of‐the‐art research in the preparation and application for the metal oxide based composite materials. Finally, we discuss key aspects, which should be addressed for design and construction. [ABSTRACT FROM AUTHOR]

Improvement in the photoelectrochemical activity of photoanodes is required to employ them in energy conversion systems. Various titanium dioxide (TiO2) films have been combined with conductive materials using diverse methods to increase the photocatalytic activity of TiO2. Recently, sol–gel electrophoretic deposition (EPD) was used to deposit composite thin films of TiO2 and multiwalled carbon nanotubes (MWCNTs) with various structures by changing the ratio of TiO2 sol to MWCNTs in an electrophoresis bath. Results indicated that the optimization of the chemical composition and morphology of the composite films are the key to improving the photoelectrochemical performance of TiO2–MWCNT thin-film electrodes. Herein, the effects of solvents on the as-prepared thin-film structures were investigated using sol–gel EPD and the photoelectrochemical performance of the thin-film electrodes. Acetone was mixed with 2-propanol to increase the deposition rate—by decreasing viscosity—and modify the solvent affinity to each solute (i.e., TiO2 sol and MWCNTs) to tune the chemical composition and morphology of the involved film for enhanced photoelectrochemical performance. The acetone/2-propanol volume ratio influenced the crystal structure (crystal size and anatase/rutile ratio) of TiO2 as well as the chemical composition and morphology of the film. The highest photocatalytic activity was obtained at an acetone/2-propanol volume ratio of 1:9, an anatase/(anatase + rutile) ratio of 94.8 wt.%, and a TiO2/C ratio of 39.4 wt.%, resulting in the largest ultraviolet adsorption by TiO2 and the smallest charge transfer resistance.Graphical abstract: Improvement in the photoelectrochemical activity of photoanodes is required to employ them in energy conversion systems. Various titanium dioxide (TiO2) films have been combined with conductive materials using diverse methods to increase the photocatalytic activity of TiO2. Recently, sol–gel electrophoretic deposition (EPD) was used to deposit composite thin films of TiO2 and multiwalled carbon nanotubes (MWCNTs) with various structures by changing the ratio of TiO2 sol to MWCNTs in an electrophoresis bath. Results indicated that the optimization of the chemical composition and morphology of the composite films are the key to improving the photoelectrochemical performance of TiO2–MWCNT thin-film electrodes. Herein, the effects of solvents on the as-prepared thin-film structures were investigated using sol–gel EPD and the photoelectrochemical performance of the thin-film electrodes. Acetone was mixed with 2-propanol to increase the deposition rate—by decreasing viscosity—and modify the solvent affinity to each solute (i.e., TiO2 sol and MWCNTs) to tune the chemical composition and morphology of the involved film for enhanced photoelectrochemical performance. The acetone/2-propanol volume ratio influenced the crystal structure (crystal size and anatase/rutile ratio) of TiO2 as well as the chemical composition and morphology of the film. The highest photocatalytic activity was obtained at an acetone/2-propanol volume ratio of 1:9, an anatase/(anatase + rutile) ratio of 94.8 wt.%, and a TiO2/C ratio of 39.4 wt.%, resulting in the largest ultraviolet adsorption by TiO2 and the smallest charge transfer resistance. [ABSTRACT FROM AUTHOR]

The wheels of the future generation will be driven by hydrogen fuel. Hydrogen is the potential, sustainable and clean energy vector, with high energy density, high heating value, and greenhouse gas-free combustion. Artificial photosynthesis especially photoelectrocatalytic (PEC) and photocatalytic (PC) water splitting reactions are widely investigated over gasification, electrolysis, thermochemical and photobiological systems for green hydrogen production. Metal Halide Perovskites (MHPs) with ABX 3 stoichiometry have piqued researcher's curiosity because of their peculiar electronic, thermal and optical properties, including long carrier diffusion lengths, outstanding tolerance factors, high light absorption coefficients, large thermal expansion coefficient and ultralow thermal conductivity. The optoelectronic properties of MHPs can be modified using band-gap tuning and defect engineering techniques, and they can be used for photocatalytic and photoelectrocatalytic applications in water splitting, nitrogen fixation, and CO 2 reduction. Many review articles have summarized the synthesis, properties and application in the above-mentioned area by using MHPs. Few review articles exclusively focused on MHP based photocatalytic systems for water splitting and there is no dedicated review article is available to date for MHP-based PEC water splitting. In this article, we reviewed the latest research trends and developments in the field of PEC water splitting using MHPs. This also provides details about the optical, electronic, and thermal aspects of MHPs, along with feasible changes, limitations, and stability concerns, as well as viable ways to overcome such hurdles. [Display omitted] • Opto-electric, thermal and structural properties of halide perovskites are summarized. • The advantages of MHPs over organic HPs for PEC application have been studied. • Strategies to overcome the stability issues of MHPs in PEC application are discussed. • This review offers future insights and perspectives on MHPs for solar water splitting. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) hydrogen production from water splitting is a green technology that can solve the environmental and energy problems through converting solar energy into renewable hydrogen fuel. The construction of host/guest architecture in semiconductor photoanodes has proven to be an effective strategy to improve solar‐to‐fuel conversion efficiency dramatically. In host/guest photoanodes, the absorber layer is deposited onto a high‐surface‐area electron collector, resulting in a significant enhancements in light‐harvesting as well as charge collection and separation efficiency. The present review aims to summarize and highlight recent state‐of‐the‐art progresses in the architecture designing of host/guest photoanodes with integrated enhancement strategies, including i) light trapping effect; ii) optimization of conductive host scaffolds; iii) hierarchical structure engineering. The challenges and prospects for the future development of host/guest nanostructured photoanodes are also presented. [ABSTRACT FROM AUTHOR]

An ideal catalytic interface for photoelectrodes that enables high efficiency and long‐term stability remains one of the keys to unlocking high‐performance solar water splitting. Here, fully decoupled catalytic interfaces realized using surface‐structured cocatalyst foils are demonstrated, allowing optimized photoabsorbers to be combined with high‐performance earth‐abundant cocatalysts. Since many earth‐abundant cocatalysts are deposited via solution‐based methods, deposition on chemical‐sensitive photoabsorbers is a significant challenge. By synthesizing cocatalyst foils prior to device fabrication, photoabsorbers are completely isolated from corrosive chemical environments and are provided with outstanding protection during operation. Si and GaAs photoelectrodes prepared using Ni‐based cocatalyst foils achieve excellent half‐cell efficiencies and generate stable photocurrents for over 5 days. Furthermore, a GaAs artificial leaf achieves a solar‐to‐hydrogen efficiency of 13.6% and maintains an efficiency of over 10% for longer than nine days, an accomplishment that has not been previously reported for an immersed solar water splitting system. These results, together with theoretical calculations of other photoelectrode systems, demonstrate that cocatalyst foils offer a very attractive method for fabricating high‐performance solar water splitting systems. [ABSTRACT FROM AUTHOR]

Abstract Photoelectrochemical (PEC) hydrogen production from water splitting is a green technology that can solve the environmental and energy problems through converting solar energy into renewable hydrogen fuel. The construction of host/guest architecture in semiconductor photoanodes has proven to be an effective strategy to improve solar‐to‐fuel conversion efficiency dramatically. In host/guest photoanodes, the absorber layer is deposited onto a high‐surface‐area electron collector, resulting in a significant enhancements in light‐harvesting as well as charge collection and separation efficiency. The present review aims to summarize and highlight recent state‐of‐the‐art progresses in the architecture designing of host/guest photoanodes with integrated enhancement strategies, including i) light trapping effect; ii) optimization of conductive host scaffolds; iii) hierarchical structure engineering. The challenges and prospects for the future development of host/guest nanostructured photoanodes are also presented.

Summary: The photoelectrochemical charge-transfer process occurring at semiconductor surfaces has important implications in the fields of solar fuels and biodetection. Usually, physical light sources located outside the liquid phase, such as a solar simulator, a light-emitting diode (LED), or a laser, are used for photoelectrochemical studies. Here, we report inducing photoelectrochemistry using an electrochemical source of light, that is, the electrochemiluminescence (ECL) emitted by a model co-reactant system. Results reveal that the ECL illumination can activate several semiconductor (SC) photoelectrodes based on n-type Si, n-type GaAs, and p-type Si. We demonstrate that this emitter-receiver concept, based on dual-light conversion, enables photoelectrochemical charge transfer at the solid/liquid interface, which correlates with the ECL intensity. The singularities of this concept lie in the fact that light emission and collection both occur in the liquid phase, that ECL is an easily miniaturizable photon source, and that the SC/liquid junction can be easily implemented. This approach may open perspectives for remote ECL detection strategies and original photoelectrochemical analytical systems.

This work reports on the preparation of Cr-doped TiO2 (Cr–TiO2), Cu-doped (Cu-TiO2), and its utilization in the photoanode of a solar redox flow battery (SRFB). A pure TiO2 electrode, Cr-doped TiO2 electrode, and Cu-doped TiO2 electrode coated with different layers are prepared by the sol-gel method. XRD, XPS, and SEM are used to characterize the relevant data of the electrode. All three electrodes show the structure of the anatase phase, but the Cu-TiO2 and Cr-TiO2 electrodes are more crystalline. Using these materials as photoelectrodes to prepare integrated solar flow cells, the semi-cell and full-cell tests show that the doping of Cr and Cu improves the efficiency and charging current of solar cells. The average charging currents of the Cu-TiO2 and Cr-TiO2 electrodes are 384.20 μA and 450.75 μA, respectively, compared with the TiO2 electrode; this increment reaches values of 71.23% and 100.97%.

Highly efficient photoelectrochemical (PEC) water oxidation under solar visible light is crucial for water splitting to produce hydrogen as a source of sustainable energy. Particularly, silver-based nanomaterials are important for PEC performance due to their surface plasmon resonance which can enhance the photoelectrochemical efficiency. However, the PEC of ZnO/Ag2WO4/AgBr with enhanced visible-light water oxidation has not been studied so far. Herein, we present a novel photoelectrodes based on ZnO/Ag2WO4/AgBr nanorods (NRs) for PEC application, which is prepared by the low-temperature chemical growth method and then by successive ionic layer adsorption and reaction (SILAR) method. The synthesized photoelectrodes were investigated by several characterization techniques, emphasizing a successful synthesis of the ZnO/Ag2WO4/AgBr heterostructure NRs with excellent photocatalysis performance compared to pure ZnO NRs photoelectrode. The significantly enhanced PEC was due to improved photogeneration and transportation of electrons in the heterojunction due to the synergistic effect of the heterostructure. This study is significant for basic understanding of the photocatalytic mechanism of the heterojunction which can prompt further development of novel efficient photoelectrochemical-catalytic materials. [ABSTRACT FROM AUTHOR]

Solar‐driven water splitting is a promising way to produce renewable hydrogen. The design of efficient semiconductor photocatalysts plays a vital role in this process. The recent dynamic development of metal–organic framework (MOF) materials provides a good opportunity to design efficient composite photocatalysts toward solar water splitting. Herein, a critical review of the design and development of MOF/semiconductor composite photocatalysts for solar‐driven water splitting is presented. The designing strategies of MOF‐based composite photocatalysts, including the use of organic ligands, quantum dots and carbon‐based materials to form heterostructures, and the combination of MOF layers with semiconductors to fabricate thin‐film photoelectrodes for photoelectrochemical water splitting, are introduced. The remaining challenges and future perspectives of the MOF‐based composites with the hope of achieving improved solar water splitting are also discussed.

Solar‐driven water splitting is a promising way to produce renewable hydrogen. The design of efficient semiconductor photocatalysts plays a vital role in this process. The recent dynamic development of metal–organic framework (MOF) materials provides a good opportunity to design efficient composite photocatalysts toward solar water splitting. Herein, a critical review of the design and development of MOF/semiconductor composite photocatalysts for solar‐driven water splitting is presented. The designing strategies of MOF‐based composite photocatalysts, including the use of organic ligands, quantum dots and carbon‐based materials to form heterostructures, and the combination of MOF layers with semiconductors to fabricate thin‐film photoelectrodes for photoelectrochemical water splitting, are introduced. The remaining challenges and future perspectives of the MOF‐based composites with the hope of achieving improved solar water splitting are also discussed. [ABSTRACT FROM AUTHOR]

The interfacial interaction between different materials is favorable to the photoexcited charge separation, and it can also contribute complete performance to their individual benefits and create for the shortcomings to attain a complementary influence. But, it is still challenging to modify the preferred structure and heterojunction interface of catalyst materials using a facile and effective method. In this report, 2D g-C 3 N 4 sheets supported 3D star-shaped flower like CuO nanohybrid p-n type heterojunction catalysts were prepared using simple facile synthesis technique and examined their catalytic activity and photoelectrochemical properties. The photocatalytic efficacies of TC using pure g-C 3 N 4 , CuO and CuO/g-C 3 N 4 were 47.4%, 75.2% and 94.7% within the 30 min of visible light irradiation. The enhanced photodegradation performance of nanohybrids catalyst is due to the formation of heterojunction, subsequent in the photoexcited charge carrier's active separation the improved ability of visible light absorption and development of p-n heterojunction. Moreover, PEC water oxidation properties were examined and CuO/g-C 3 N 4 nanohybrid electrodes displays improved PEC properties than the pure CuO and g-C 3 N 4. Furthermore, g-C 3 N 4, CuO and CuO/g-C 3 N 4 photoelectrode displays photocurrent density 0.85, 1.60 and 2.30 mA/cm−2, respectively. Therefore, 3D/2D nanohybrids with robust ability of visible light absorption could offer a novel method to create effective facilitating the growth of photoelectrodes for the PEC water oxidation and photodegradation for fast and effective antibiotic removal from the environment. [Display omitted] • 2D g-C 3 N 4 /3D star shaped flower CuO catalysts were prepared by facile method. • CuO/g-C 3 N 4 is used to study their degradation and photoelectrochemical performance. • CuO/g-C 3 N 4 showed 94.7% removal of tetracycline within 30 min of visible light. • Composite electrode showed ∼5.4 and 2.5 folds improved photocurrent density. [ABSTRACT FROM AUTHOR]