Search Results (285)

Hydrogen is acknowledged as a clean and sustainable energy source due to the increasing demand for renewable energy sources. Photoelectrochemical (PEC) water splitting presents a viable approach for directly producing hydrogen from solar energy with negligible implications for the environment. However, regardless of the intensive studies over several years, a major hurdle to translating impressive laboratory-scale efficiency into robust, dependable, large-scale production of hydrogen is increasing competition from quickly advancing photovoltaic (PV)–based electrolysis technology. In parallel, Z-scheme or S-scheme artificial leaf catalyst systems mimicking photosynthesis are gaining ground in the research community. The performance and reliability of photo-electrocatalytic large-scale hydrogen production should be evaluated via pilot-scale and field studies, along with life cycle and economic studies. In the present manuscript, a comprehensive overview of technologies related to scalability is presented, with a focus on semiconductor materials and reactor design. In conclusion, problems and opportunities for future research on large-scale production technologies are presented. Full article

Aerosol-assisted chemical vapor deposition (AACVD) was used to prepare a thin film of the heterojunction MnO₂/WO₃ onto an FTO glass substrate. The WO₃/MnO₂ heterojunction thin film exhibited a monoclinic WO₃ structure characterized by a nanorod-like shape and substantial interfacial bonding. The detected surface area of the WO₃/MnO₂ thin film is 32.58 ± 0.79 μm², while the values of R_a and R_q are 23.20 ± 2.26 nm and 29.60 ± 2.40 nm, respectively, which are higher than pure MnO₂ (R_a =13.40 ± 0.99 nm), while lower than pure WO₃ (R_a = 69.75 ± 1.34 nm) thin films. The UV–Vis spectra demonstrated extensive absorption in the visible to near-infrared range. The absorption spectrum of UV–Vis (200–900 nm) displayed a distinct absorption edge under 400 nm. The band gap of the pure WO₃ thin film equals 2.79 eV, whereas an effective band gap of WO₃/MnO₂ was observed to equal 1.51 eV, which is significantly smaller than that of the individual oxides (MnO₂ = 4.47 eV and WO₃ = 2.79 eV). Photoluminescence (PL) verified the robust interfacial electronic interaction. The investigation of the PEC performance exhibited the best performance and the greatest photocurrent under illumination than either pure component. Additionally, there was a good enhancement and improvement in the charge separation due to combining the catalytic MnO₂ thin film with a photoactive WO₃, owing to its effective charge transfer and decreased recombination. Full article

This study explores the multifunctional properties of Ni nanoparticles obtained by laser ablation in liquid, with emphasis on the potential use of these nanoparticles in different applications such as cooling fluids or photoelectrochemical ones. The Ni nanoparticles were synthesized by the laser ablation in liquid technique using an Nd-YAG laser and ultrapure water as liquid. The structural, dimensional, morphologic, and stoichiometric characterizations of the nanoparticles were performed using different techniques such as transmission electron microscopy (TEM), energy dispersive X-ray (EDS) and dynamic light scattering spectroscopy (DLS). Nickel nanoparticles with sizes ranging from 5 to 15 nm in diameter were obtained. The experimental measurements were performed to determine the thermal conductivity and viscosity of the obtained nanofluids, essential parameters in the evaluation of the cooling fluid performances. Loading TiO₂ thin films with Ni nanoparticles led to the enhancement of the photoelectrochemical water splitting properties of TiO₂ thin films, the Ni nanoparticles acting on the collecting, transferring and separating the photogenerated charges and ultimately improving the overall anodic and cathodic efficiencies. The results obtained can contribute to the development of innovative, multifunctional solutions based on non-precious metals for cooling and water splitting systems used in industrial, electronics and other applications. Full article

Developing efficient photoelectrocatalysts is crucial for advancing sustainable energy solutions to generate green hydrogen, particularly in photoelectrochemical water splitting. This study addresses these limitations by synthesizing and characterizing WO₃/(W)BiVO₄ heterojunctions incorporated with graphitic carbon nitride (C₃N₄). Our approach combines a microwave-assisted synthesis for heterojunction formation with the direct polymerization of C₃N₄, aiming to enhance the charge separation and light absorption. Structural and morphological analyses confirmed the presence of well-defined heterojunctions with homogeneous element distributions, while spectroscopic studies demonstrated enhanced visible light absorption. Our results show the potential of WO₃/(W)BiVO₄/C₃N₄ systems as durable and efficient photoanodes. The further optimization of polymerization conditions and band alignment strategies may unlock greater efficiency, paving the way for more effective solar-driven hydrogen production. Full article

The development of efficient visible-light-driven semiconductor photocatalysts is essential for scalable and sustainable green hydrogen production. Among ternary metal oxides, MV₂O₆ (M = Zn, Ni, Cu, Mn, Co, etc.) metavanadates have attracted considerable interest because of their narrow band gaps (~1.8–2.5 eV), strong visible-light absorption, and unique edge-sharing VO₆ octahedral framework that promotes charge separation. This review summarizes recent advances in the design, synthesis, and electronic engineering of MV₂O₆-based photocatalysts for solar water splitting. Since direct particulate overall water splitting has only been demonstrated for MnV₂O₆, whereas ZnV₂O₆, NiV₂O₆, and CuV₂O₆ have mainly been investigated as photoelectrodes, both particulate photocatalytic and photoelectrochemical (PEC) systems are critically examined. The review clearly distinguishes these two configurations, highlighting how PEC studies provide valuable insights into charge transport, interfacial processes, and reaction kinetics while recognizing the additional challenges associated with suspension-based photocatalysis. Fundamental crystal structures, electronic band alignments, and charge-transfer characteristics of MV₂O₆ compounds are discussed, followed by recent advances in synthesis strategies, including hydrothermal, sol–gel, and deep eutectic solvent (DES)-assisted methods, together with morphology and defect engineering. Particular attention is given to oxygen-vacancy formation and its influence on visible-light absorption and charge separation. Modification strategies, including elemental doping, cocatalyst loading, and the construction of Z-scheme and step-scheme (S-scheme) heterojunctions, are critically evaluated for improving photocatalytic efficiency. Finally, the review discusses the key challenges that limit practical applications, including unfavorable band-edge positions, rapid carrier recombination, sluggish surface reaction kinetics, photostability, and the need to establish composition–structure–activity relationships. Future perspectives emphasize rational materials design through advanced characterization, theoretical calculations, and scalable synthesis approaches to accelerate the development of efficient MV₂O₆ photocatalysts for solar-driven hydrogen production. Full article

In this work, we performed a comprehensive first-principles investigation of the electronic structure, charge carrier relaxation dynamics, and photoluminescence properties of Rh-doped BaTiO₃, with a focus on photocatalytic water splitting applications. By combining hybrid DFT (HSE06), DFT+U, and Redfield theory, we elucidated how the doping site (Ti vs. Ba), dimensionality (bulk vs. surface), and aqueous environment govern the nonequilibrium behavior of photogenerated electron–hole pairs. Rh occupying Ti sites on the (001) surface exhibits a unique combination of extended visible-light absorption, ultrafast non-radiative relaxation, and efficient charge separation. These characteristics establish it as a promising photoanode material for photoelectrochemical water splitting. Full article

In this study, a fully coupled three-dimensional multiphysics CFD model of a photoelectrochemical (PEC) water splitting cell incorporating a ZnO/BiVO₄ photoanode was developed using COMSOL Multiphysics^® 6.1. The model integrates semiconductor charge transport, ionic transport (diffusion, migration, and convection), electrochemical kinetics, and fluid dynamics within a widely adopted experimental configuration. This work focuses on coupling the dominant transport phenomena governing macro-scale PEC behavior under realistic operating conditions, allowing the overall PEC behavior to be captured without resolving microscopic interfacial complexities. The simulation results show good agreement with previously reported experimental data in terms of photocurrent density, demonstrating the capability of the model to reproduce photocurrent behavior. The developed framework provides insight into the interplay between photogenerated charge transport and electrochemical reactions and can serve as a predictive tool for analyzing and optimizing PEC system performance prior to experimental implementation. Full article

Elucidating structure–activity relationships in semiconductor photocatalysis has been significantly impeded by the inherent limitations of ensemble-averaged characterization techniques, which obscure the spatiotemporal heterogeneity intrinsic to catalytic surfaces. Single-molecule fluorescence microscopy (SMFM) surmounts this bottleneck by offering nanometer-scale spatial resolution coupled with the capacity to resolve single-turnover events. Herein, we provide a comprehensive overview of the State-of-the-Art applications of fluorogenic probe-coupled SMFM in deciphering the microscopic mechanisms governing photocatalysis. We begin by delineating the operational principles of total internal reflection fluorescence (TIRF) microscopy and categorizing the response mechanisms of three distinct classes of fluorogenic probes: oxidative (e.g., Amplex Red, APF), reductive (e.g., Resazurin, DN-BODIPY), and acidic (e.g., furfuryl alcohol, thiophene) reporters. Subsequently, we highlight seminal studies wherein SMFM has been leveraged to visualize facet-dependent charge separation on model photocatalysts—including TiO₂, BiOBr, and InSe—to map the dynamic activity associated with surface defects and to precisely locate active sites during photoelectrochemical water splitting. Finally, we critically assess the prevailing technical challenges, such as limitations in probe specificity and background interference, while offering a perspective on prospective avenues for methodological refinement. This review is intended to serve as a methodological cornerstone for advancing mechanistic understanding in photocatalysis and for guiding the rational design of high-performance catalysts. Full article

Photocatalytic water splitting for hydrogen (H₂) evolution is a critical sustainable energy strategy, and cadmium sulfide (CdS) is a promising visible-light photocatalyst due to its suitable band gap. However, the practical application of pure CdS is severely hindered by rapid charge-carrier recombination and significant photocorrosion. In this work, we constructed a CdS/vanadium carbide (VC) photocatalyst via a simple ultrasonic method. The structural, morphological, optical, and photoelectrochemical properties of the composites were systematically investigated. Under visible light (λ ≥ 420 nm) and with 0.35 M Na₂S-0.25 M Na₂SO₃ as the sacrificial agent, the optimized composite featuring a CdS:VC mass ratio of 10:1 (denoted CV-10) achieved a remarkable hydrogen evolution rate of 3485.6 μmol g⁻¹ h⁻¹. This rate represents a 60-fold enhancement over pure-phase CdS and significantly surpasses that of a conventional Pt/CdS catalyst. Furthermore, the CV-10 composite demonstrated excellent stability, showing no activity decay after 16 h of cycling. Spectroscopic and electrochemical analyses revealed that the metallic VC can function as an efficient cocatalyst, accelerating charge separation and transfer while suppressing electron–hole recombination. This work demonstrates that noble-metal-free VC is a highly effective and low-cost cocatalyst, providing a new pathway for designing efficient and stable CdS-based photocatalysts in solar hydrogen production. Full article

Graphitic carbon nitride (CN) is a promising photocatalytic material, but its practical application is limited by small specific surface area, narrow light absorption range, and high photogenerated carrier recombination rate. To address these issues, this study synthesized boron-doped carbon nitride (BCN) and sulfuric acid-exfoliated boron-doped carbon nitride (BCND). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed that boron was successfully doped into the CN skeleton via B-N bonds. Scanning electron microscopy (SEM) and N₂ adsorption–desorption (BET) characterizations showed that acid exfoliation significantly increased the specific surface area of BCND to 68.80 m²·g⁻¹, much higher than that of CN (9.54 m²·g⁻¹) and BCN (15.98 m²·g⁻¹). UV–visible diffuse reflectance spectroscopy (UV-Vis DRS) analysis revealed that BCND had the narrowest bandgap (2.59 eV) among the three materials, which enhanced its visible-light absorption efficiency. Photoelectrochemical tests demonstrated that BCND exhibited the smallest charge transfer resistance and the highest transient photocurrent density (eight times that of CN), indicating efficient separation of photogenerated electron–hole pairs. Photocatalytic water splitting experiments showed that BCND achieved the highest Hydrogen production rate of 792.34 μmol·g⁻¹·h⁻¹, which was about 4 times that of CN (158.41 μmol·g⁻¹·h⁻¹) and 1.36 times that of 2.5% BCN (584.30 μmol·g⁻¹·h⁻¹). Free-radical trapping experiments indicated that hydroxyl radicals (·OH) played a crucial promotional role in Hydrogen production, while superoxide anions (·O₂⁻) exerted an inhibitory effect. The enhanced performance of BCND was attributed to the synergistic effects of boron doping (narrowing bandgap) and acid exfoliation (increasing specific surface area). A possible photocatalytic Hydrogen production mechanism was proposed based on the experimental results. This study provides a feasible strategy for the structural modification and performance optimization of g-C₃N₄-based photocatalysts for water splitting. Full article

The photoelectrochemical water-splitting process for hydrogen production is limited by the large bandgap of semiconductor titanium dioxide (TiO₂) and by interfacial recombination at particle interfaces. The technique used in this paper is that of electrochemical anodization to produce robust, ordered TiO₂ nanotube arrays (TiO₂ nanorod arrays denoted as TNTAs). Using the immersion-annealing method, Nd₂O₃ nanoparticles can be immobilized in situ, and Nd₂O₃/TNTAs composite photoanodes are fabricated. The heterointerface caused between the Nd₂O₃ nanoparticles and TiO₂ results in the alignment of the Fermi levels and the formation of band bending and an internal electric field at the interface. It allows rapid photo-generated electron-hole (e⁻/h⁺) separation at the interface and, simultaneously, introduces novel localized electron states of Nd³⁺ within the TiO₂ bandgap. This triggers hybridisation between the 3d orbitals of Ti and the 2p orbitals of O, thereby altering the band structure of TiO₂. The best-performing Nd₂O₃/TNTAs photoelectrode outperforms pure TNTAs, with a photocurrent density of 1.59 mA·cm⁻² at 1.23 V vs. RHE. It produces 162.6 μmol·cm⁻² of hydrogen in a 3 h photocatalytic hydrogen production experiment, which is about 12.2 times that of pure TNTAs. This approach highlights the unique benefits and creative opportunities of applying rare-earth elements to address the critical issues of photocatalysts, such as significant band gaps and rapid recombination. Full article

Mixed-halide perovskite solar cells with the composition Cs_0.1(MA_0.17FA_0.83)_0.9Pb(I_0.83Br_0.17)₃ were fabricated obtaining solar cells as glass/ITO/SnO₂/triple-cation perovskite/HTL/Au, and subsequently used as photoanodes for efficient solar-driven water splitting by attaching commercial catalytic nickel foils to the Au back-contact pads of solar cells. To enable operation in alkaline media, the devices were encapsulated using commercial PET–EVA multilayer films, providing an effective barrier while leaving the Ni foils exposed as the electrochemically active interface. Two operating configurations were investigated and compared: (i) an outside configuration, where the perovskite device powered the external electrochemical cell, and (ii) an immersed configuration, in which the encapsulated perovskite solar cell was directly integrated, together with the Ni catalyst, into the electrolyte. In both configurations, the onset potential for the oxygen evolution reaction shifted from ~1.32 V vs. RHE, when the Ni electrode was not powered by the perovskite solar cell, to ~0.34 V vs. RHE, when the perovskite device powered the Ni foil for both immersed and outside configurations. The immersed configuration delivered the highest performance, achieving a maximum Applied Bias Photon-to-Current Efficiency of ~20% under AM 1.5 G illumination (100 mW cm⁻²), among the highest values reported for perovskite-based photoanodes. Importantly, the enhanced performance does not arise from changes in catalyst composition or direct semiconductor–electrolyte interaction, but from improved photovoltage delivery and reduced resistive losses enabled by the integrated device architecture. These results demonstrate that device architecture is a key factor in controlling photovoltage utilization and charge-transfer kinetics, providing a viable strategy for efficient and scalable perovskite-based photoelectrochemical systems. Full article

The photoelectrochemical splitting (PEC) of water provides a direct route to converting solar energy into storable chemical fuels. When illuminated, a semiconductor photoelectrode can absorb light and generate electron-hole pairs, which participate in interfacial redox reactions at the semiconductor-electrolyte junction. Therefore, to achieve high-performance PEC, photoelectrodes with optimized optical absorption and charge have been explored. This review analyzes recent fabrication strategies used to design photoelectrodes for the PEC dissociation of water. Physical fabrication techniques, including pulsed laser deposition, magnetron sputtering, and physical vapor deposition, allow for precise control of film thickness, crystallinity, and defect density, critical parameters for efficient charge transport. Typically, in physical methods, reported photocurrent densities span from ~10⁻² to 10¹ mAcm⁻², depending on the semiconductor material, nanostructure design, and interfacial engineering strategies. Chemical synthesis methods, such as hydrothermal growth, successive ion layer adsorption and reaction, and microemulsion techniques, provide greater compositional flexibility and enable controlled doping, surface functionalization, and the formation of nanostructured morphologies. Finally, hybrid fabrication strategies integrate physical and chemical processes within a single synthesis framework to combine structural precision with compositional tuning capabilities. These approaches enable the development of advanced architecture such as heterojunctions, core–shell nanostructures, and catalyst-modified interfaces, which enhance light absorption and optimize interfacial transfer. Furthermore, theoretical and computational tools are here analyzed as complementary approaches that guide the rational design and optimization of photoelectrochemical materials and devices. Full article

Photoelectrochemical (PEC) water splitting offers a sustainable route for solar-to-hydrogen conversion, yet its large-scale deployment is often hindered by energy-intensive and costly fabrication processes for semiconductor photoelectrodes. Electrodeposition provides an attractive alternative owing to its solution-based, low-temperature, and scalable nature; however, the relationship between electrochemical deposition parameters and photoelectrode functionality remains insufficiently understood. Herein, we systematically investigate system-level control in electrodeposition for photoelectrode synthesis using BiVO₄ photoanodes and CuO/Cu₂O photocathodes as model systems. By modulating deposition potential, current density, and electrical control modes, we elucidate how interfacial ion dynamics and growth kinetics govern film morphology, phase evolution, and PEC performance. DC electrodeposition establishes a baseline structure–performance relationship governed by precursor concentration and current density, while pulsed operation enables decoupling of nucleation and growth, leading to refined nanostructures and enhanced photocurrent responses. Further incorporation of reverse-pulsed potentials provides dynamic interfacial reset, enabling precise control over porosity and grain connectivity. The optimized BiVO₄ photoanodes fabricated under tailored reverse-pulsed conditions exhibit improved photocurrent density compared to continuously deposited counterparts. The insights presented here provide practical guidelines for rationally engineering high-performance, scalable, and environmentally benign photoelectrodes for PEC water splitting. Full article

The transition to clean and renewable energy sources is of prime importance in addressing environmental challenges related to the consumption of fossil fuels. Hydrogen, being a clean fuel with a high energy density, has huge potential, especially when it can be obtained through solar-driven PEC water splitting. Herein, $Mo{S}_2$ photocatalysts were synthesized by sulfurizing $Mo{O}_3$ thin films, using a CVD technique. The deposited $Mo{O}_3$ films by thermal evaporation at 450 °C were further sulfurized at 500 °C, 550 °C, and 600 °C. XRD results confirmed the successful conversion of $Mo{O}_3$ into $Mo{S}_2$. The optical properties showed a bandgap reduction from 2.50 eV to 1.30 eV, which leads to better absorption of light in the visible region.The photoelectrochemical experiment shows that the S-$Mo{O}_3$-600 °C thin film has the best performance, and the solar-to-hydrogen conversion efficiency reaches 0.11385% at an applied bias of 1.0 V versus Ag/AgCl, which is about 189 times higher than that of the pristine $Mo{O}_3$ thin film. Full article