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The consumption of fossil fuels releases large amounts of carbon dioxide (CO2) in the atmosphere, causing a serious greenhouse effect. Photoelectrochemical (PEC) reduction of CO2 to chemical fuels is an effective way to alleviate the current energy and environmental crisis. However, it is still difficult to rationally design efficient PEC CO2 reduction photocathodes. Cuprous oxide (Cu2O) is a promising photocathode material, but its surface is susceptible to the accumulation of photogenerated electrons leading to corrosion and activity reduction, and is accompanied by hydrogen evolution reaction (HER), both of which lead to the overall low conversion efficiency of CO2 reduction by Cu2O. In this study, the PEC CO2 conversion efficiency was improved by the synergistic effect of the C electron transport layer to accelerate the electron transfer to alleviate the Cu2O corrosion problem and the polytetrafluoroethylene (PTFE) hydrophobic layer to inhibit the HER. The test showed that the CO yield of Cu2O/C/PTFE at the optimum potential (−0.7 V vs. RHE) was 54.6 μmol cm−2 h−1, which was 3.2 times higher than that of pure Cu2O. This study provides a facile strategy for constructing an efficient photocathode with great potential for CO2 reduction. [ABSTRACT FROM AUTHOR]

Particle transfer method photoelectrodes show superior photoelectrochemical performance compared to traditional powder‐based methods, making them a promising solution for solar water splitting in sustainable energy. This study introduces an innovative nonvacuum particle transfer method for fabricating photoelectrodes on a conductive carbon substrate, addressing the challenges associated with the high costs and vacuum deposition processes of traditional methods. Utilizing a p‐type CuFeO2 powder semiconductor, a unique substrate is developed by applying a graphene oxide layer mixed with a small amount of silica binder on the particle layer's backside through ultrasonic atomization spraying. This layer is converted into multilayered reduced graphene oxide (ML‐rGO) via wet chemical reduction, resulting in a substrate boasting a high work function (4.8 eV), alongside remarkable chemical stability, mechanical strength, and conductivity. The fabricated CuFeO2 photocathode demonstrated an onset potential of 0.97 V versus RHE and a photocurrent density of 1.5 mA cm−2 at 0.6 V versus RHE for H2O2 reduction. Further enhancement is achieved by depositing Pt as a cocatalyst, which ensured stability for over 20 h in an alkaline medium for water splitting. This study sets a new benchmark for developing CuFeO2‐based photocathodes, paving the way for broader particle transfer method applications. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu2O) is a promising photocathode material for unbiased solar water splitting cells. To improve the onset potential of Cu2O photocathodes, numerous efforts have been devoted to exploring a suitable n-type buffer layer material. However, previous studies mostly focused on optimizing the band alignment between the absorber and buffer layer, ignoring the role of surface states as reaction intermediates. Moreover, the high cost of Ga element and complicated multilayer process in current Ga2O3-based devices impede their large-scale application. In this work, the photoelectrochemical (PEC) performance of Cu2O photocathodes was investigated by coating an amorphous and crystalline WO3 buffer layer with an annealing temperature of 100 and 200 °C, respectively. It is found that the onset potential of the Cu2O photocathode anodically shifts from 0.7 to 0.95VRHE with an amorphous WO3 coating, while a poorer PEC performance is observed on the electrodes with crystalline WO3 coating. Further analysis indicates that the porous structure and photocapacitive surface states on the amorphous WO3 layer provide a special electron-transfer pathway into the electrolyte, which is eliminated in the crystalline WO3 layer. Our study offers a strategy for enhancing the photovoltage of photocathodes instead of optimizing band alignment. [ABSTRACT FROM AUTHOR]

This research presents a non-traditional method for surface modification. a Cu2O/CuO heterostructure was prepared on Cu foil by a dielectric barrier discharge (DBD) plasma and used as a photocathode for photoelectrochemical (PEC) water splitting. Cu2O/CuO heterostructure was prepared at 1 min, 3 min, and 6 min exposures of the Ar/O2 gas mixture using DBD plasma, followed by the calcination process at 200 °C for 2 hours. The samples were applied toward PEC water splitting. The samples' X-ray diffraction (XRD) pattern confirmed the cubic phase of Cu2O and the monoclinic phase of CuO. The field emission scanning electron microscope (FE-SEM) images show that the sample after 1 min of plasma exposure consists of a broccoli-like microstructure, and by increasing the duration time to 3 min and 6 min, the microwire structure was prepared. The presence of minuscule nanoparticles on the surface of all microstructures leads to an elevation in aspect ratio and charge carrier density, resulting in improved performance in photoelectrochemical (PEC) properties. The highest photocurrent of 6.53 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) was recorded for Cu2O/CuO heterostructure prepared at 3 min exposure plasma under AM 1.5G irradiation. A longer exposure time of DBD plasma causes more thickness and increases the recombination of charge carriers, which decreases the photocurrent density to 4.32 mA/cm2 at 1.23 VRHE. This study demonstrates the development of a Cu2O/CuO heterostructure on Cu foil with a high aspect ratio as a promising method for enhancing the photoresponse of the Cu2O/CuO photocathode in the context of photoelectrochemical (PEC) water splitting. [ABSTRACT FROM AUTHOR]

Greenhouse gases released into the atmosphere cause climate change on a global scale, therefore, it is urgently necessary to switch to energy production systems using renewable energy sources. Hydrogen gas production with solar energy, one of the renewable energy sources, is promising because it is sustainable and environmentally friendly. The n-type/p-type semiconductors are used for photo-electrochemical hydrogen production and their photocatalytic and photostability properties need to be improved. Cr2O3, a p-type semiconductor, has the advantages of being photostable and showing absorption in the visible region. In this study, p-type Cr2O3 semiconductor was deposited on fluorine-doped tin oxide (FTO) by hydrothermal methods with and without glucose (G) and KCl. The photocatalytic performance of the electrodes was investigated in the hydrogen evolution reaction (HER) as a photocathode for photoelectrochemical water splitting. The electrode characterization of the crystalline structure of the photoelectrodes was carried out by X-ray diffraction (XRD), surface topography by field emission scanning electron microscopy (FESEM), sunlight absorption by UV-vis spectrometry. The photocatalytic performance in the HER process was performed by linear sweep voltammetry (LSV). Resistance and capacitance values of the electrical double layer were determined by electrochemical impedance spectroscopy (EIS) and photostability tests were performed by chronoamperometric measurement. FESEM images showed that the deposition bath containing G/KCl by hydrothermal method improved the surface homogeneity and synthesized smaller nanosized Cr2O3 compared to those without glucose. XRD pattern measurement showed that Cr2O3 electrodes were synthesized with hexagonal structure in all media and conditions. LSV measurement shows that the G/KCl electrode exhibits higher photocatalytic performance as a p-type semiconductor. [ABSTRACT FROM AUTHOR]

Micropyramid Si/In 2 O 3 /CuO/ZnO photocathode and Ni/BiVO 4 photoanode have been synthesized using a magnetron sputtering method with different conditions and characterized for a photoelectrochemical water-splitting process. The as-designed heterojunction of Si/In 2 O 3 /CuO/ZnO photocathode successfully induces a facile electron transfer to generate hydrogen in 0.5 M H 2 SO 4. Similarly, Ni/BiVO 4 photoanode evolves oxygen in 0.1 M Na 2 B 4 O 7. Both photoreactions are done under concentrated solar-light irradiation (AM 1.5G, 500 mA/cm2). The analysis shows that IPCE values of photocathode and photoanode reached 40 and 60 % at 300 and 400 nm wavelengths, respectively. Furthermore, the ABPE of photocathode and photoanode achieved 14.9% and 0.8% at 0.21 and 1.15 V RHE , respectively. Photoelectrochemical analysis indicates that half cells of the photocathode and photoanode can reach photocurrents of ∼120 and ∼20 mA/cm2 at 0 and 1.23 V RHE , respectively. The outstanding performances indicate a facile charge transfer during redox reactions at the photocathode and photoanode. In addition, combining the photoelectrodes to form a cell configuration of Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 with a proton exchange membrane generates an unbiased photocurrent of 0.26 mA/cm2 at 0.55 V RHE. The combined cell has been tested for its stability in splitting water molecules into hydrogen and oxygen, indicating a promising result to overcome energy and environmental issues. [Display omitted] • Micropyramid Si/In 2 O 3 /CuO/ZnO and Ni/BiVO 4 thin-film photoelectrodes are successfully synthesized. • Si/In 2 O 3 /CuO/ZnO photocathode can induce ∼120 mA/cm2 at 0 V RHE under light illumination. • Ni/BiVO 4 photoanode delivers ∼20 mA/cm2 at 1.23 V RHE under light illumination. • The combine cell of Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 generates ∼37 mA/cm2 at 1.23 V RHE. • Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 cell shows a stability in water-splitting process. [ABSTRACT FROM AUTHOR]

A nanocomposite thin film with a moon-like structural configuration, comprised of dichalcogenides (CoS2)-CoO/Poly-2-aminothiophenol (CoS2-CoO/P2ATP), is synthesized utilizing a Co(NO3)2 and K2S2O8-driven oxidation polymerization reaction. This nanocomposite boasts impressive morphological characteristics, coupled with a noteworthy optical feature characterized by a bandgap of 1.95 eV. Hydrogen generation tests are conducted using eco-friendly, cost-effective, and readily available Red Sea water, without the need for any additional electrolytes. These experiments are conducted under various optical conditions, and the resulting Jph values are employed as an indicator of hydrogen generation efficiency. The Jph value experiences a substantial increase, transitioning from − 0.092 to − 0.13 mA/cm2 when moving from darkness to light conditions. Furthermore, under monochromatic light, the Jph values exhibit a discernible pattern, declining from − 0.175 to − 0.122 mA cm−2 as the wavelength increases from 340 to 540 nm. The consistent stability of the photocurrent for a duration of 1200 s underscores the exceptional stability and reproducibility of this photocathode in facilitating the hydrogen generation reaction. Moreover, elevating the temperature from 30 to 50 °C leads to a notable augmentation in the generated Jph, with values rising from − 0.13 to − 0.2 mA/cm2, respectively. This variation allows for the estimation of the reaction's heat, revealing a ΔH value of − 15.2 kJ/mol, indicating a spontaneous reaction and high hydrogen generation efficiency. This groundbreaking study paves the way for industrial applications of the polymer nanocomposite, enabling efficient, cost-effective, and environmentally friendly green hydrogen generation from Red Sea water. [ABSTRACT FROM AUTHOR]

In this paper, three structures (cylinder, square column, and hexagonal prism) of InGaAsP nanowire arrays are designed based on the excellent light trapping effect of nanostructures. The effects of nanowire aperture, array period, and nanowire height on the light absorption properties are simulated and analyzed using the finite-domain time-difference (FDTD) method. The photoelectron emission capacity of the nanowire arrays was also calculated using MATLAB. The results show that the cylindrical nanowire array has phenomenon of resonance enhancement (absorption peak) in the near-infrared band of 820–1000nm, and the shift of absorption peaks can be achieved by adjusting the geometric parameters. Meanwhile, the quantum efficiency is taken to 9.98%. These simulation results provide some reference for the photocathode design of InGaAsP in the near-infrared band. [ABSTRACT FROM AUTHOR]

An external electric field-assisted method is proposed to improve the electron collection capability of InGaN photocathode. We use the diffusion drift equation to calculate the photoemission performance of the nanowire arrays. The results show that nanowire array has better electron collection ability with the aid of external electric field. When the incidence angle is 88∘ and 70∘, the quantum efficiency and collection efficiency reach the maximum respectively. When the external electric field is 0.6 V/ μ m, the maximum collection efficiency is 34.2%. Compared with no electric field, the electron collection ratio increased by 69.4%. The external electric field- assisted InGaN photocathode can significantly improve the photoelectric emission performance, which is expected to be realized in future experiments. [ABSTRACT FROM AUTHOR]

Photoelectrochemistry is used to develop solar energy technologies for fuel production and chemical transformations. Semiconductor materials such as TiO2, WO3, BiVO4, Fe2O3, and Cu2O are often investigated in devices designed to convert light energy into chemical energy, including for the production of hydrogen by photoelectrochemical (PEC) water splitting. The oxide electrodes are of significant interest due to their potential for efficient PEC reactions with high durability and their relatively low costs compared to other semiconductor materials. This review highlights the roles played by macroporous photoelectrodes in the development of highly efficient photoelectrodes and advanced PEC systems using polymer electrolytes. Three‐dimensional conductive fiber substrates, such as titanium felt and carbon paper, outperform their two‐dimensional counterparts owing to their larger interfacial areas that enhance PEC properties. The macroporous structures facilitate mass‐transport‐limited reactions when integrated with polymer electrolytes in membrane electrode assemblies. Such configurations are promising for PEC splitting of pure water, and for transforming gaseous molecules such as water vapor, volatile organic compounds, and methane. Optimizing the configuration, including electrode materials selection and ionomer‐coating treatment, can potentially improve the performance of polymer electrolyte membrane PEC cells. Porous transport photoelectrodes integrated with proton/anion‐exchange membranes offer significant opportunities for advanced PEC applications. [ABSTRACT FROM AUTHOR]

A concept of solar energy convertible zinc-air battery (SZAB) is demonstrated through rational design of an electrode coupled with multifunction. The multifunctional electrode is fabricated using nitrogen-substituted graphdiyne (N-GDY) with large π-conjugated carbonous network, which can work as photoresponsive bifunctional electrocatalyst, enabling a sunlight-promoted process through efficient injection of photoelectrons into the conduction band of N-GDY. SZAB enables direct conversion and storage of solar energy during the charging process. Such a battery exhibits a lowered charge voltage under illumination, corresponding to a high energy efficiency of 90.4% and electric energy saving of 30.3%. The battery can display a power conversion efficiency as high as 1.02%. Density functional theory calculations reveal that the photopromoted oxygen evolution reaction kinetics originates from the transition from the alkyne bonds to double bonds caused by the transfer of excited electrons, which changes the position of highest occupied molecular orbital and lowest unoccupied molecular orbital, thus greatly promoting the formation of intermediates to the conversion process. Our findings provide conceptual and experimental confirmation that batteries are charged directly from solar energy without the external solar cells, providing a way to manufacture future energy devices. [ABSTRACT FROM AUTHOR]

Photoelectrochemical water splitting is a promising technology for H2 generation via water splitting reaction using the semiconductor material. In this research, the ZnFe2O4/Cu2O nanorod was investigated. The products were synthesized by the electrochemical deposition method. The characteristics of materials were investigated by X-ray diffraction, scanning electron microscopy, and UV-visible spectroscopy. All materials exhibited the ptype photoelectrode characteristic. The performance of photoelectrochemical electrodes was studied by linear swept voltammetry, electrochemical impedance spectroscopy, and Mott-Schottky analysis. The best condition deposition was by applying -0.4 V and 10 min. The highest photocurrent density was 0.8 mA.cm-2 at -0.5 (vs. Ag/AgCl) bias voltage. [ABSTRACT FROM AUTHOR]

A novel iridium (III) complex bearing boron dipyrromethene (Bodipy) as the light-harvesting antenna has been synthesized and is firstly employed as photosensitizer to assemble a dye-sensitized NiO photocathode. The assembled photocathode exhibits significantly improved photoelectrochemical (PEC) performance. Integrating the prepared photocathode with hybridization chain reaction (HCR)-­based signal amplification strategy, a cathodic PEC biosensor is proposed for the detection of microRNA-133a (miRNA-133a). In the presence of the target, HCR is triggered to form long duplex concatamers on the photocathode, which allows numerous manganese porphyrins (MnPP) to bind in the dsDNA groove. With the help of H2O2, MnPP with peroxidase-like activity catalyzes 4-­chloro-1-naphthol (4-CN) to produce benzo-­4-­chlorohexadienone (4­CD) precipitate on the electrode, leading to a significant decrease of photocurrent signal. The decreased photocurrent correlates linearly with the target concentration from 0.1 fM to 1 nM with a detection limit of 66.2 aM (S/N = 3). The proposed PEC strategy exhibits delightful selectivity, reproducibility and stability. [ABSTRACT FROM AUTHOR]

Abstract—The chemical state of MoSx catalytic layers and interfaces with p-type silicon (p-Si) and p–n-junction silicon (pn-Si) at various stages of preparation and operation of photocathodes is studied. The SiOx oxide layer formed at the interface noticeably suppresses the photocurrent for p-Si cathodes, but its removal in the HF solution provides high photocurrents exceeding the values characteristic of pn-Si cathodes at zero potential. Studies of the energy bands show that, at all stages (after the formation of the photocathode, pre- and post-processing in acid solutions), the configuration of the energy bands for p-Si and pn-Si photocathodes provides charge transfer for the evolution of hydrogen according to the Z-scheme. The difference in the characteristics of p-Si and pn-Si photocathodes is due to the possible dependence of the photovoltage in the surface layer of p-Si on the state of the interface with the catalyst film, which does not affect the photovoltage in pn-Si. [ABSTRACT FROM AUTHOR]

The results of the study on the impact of continuous visible laser irradiation on the field emission properties of point cathodes which are diamond needle-like microsized crystallites with a nanometer tip radius, are presented. The measurements were conducted in a vacuum diode configuration with a flat metal anode using DC voltage source. An increase in the field emission current was observed when the diamond needle was illuminated by laser radiation. The magnitude of the current changes directly proportional to the power of the radiation. At a maximum power density value of about 400 W/cm , the relative increase in current under the action of laser irradiation was 13 . The relative increase in current is determined by the parameters of the dark current–voltage characteristic and reaches its maximum value in the region corresponding to the minimal increase in dark current with voltage. It is shown that the most probable mechanism for the current increase is the change in the electrical resistance of the diamond microneedle as a result of the absorption of laser radiation with the involvement of electronic levels located in the bandgap of diamond, associated with impurities or structural defects in the near surface layer of the diamond microneedle. [ABSTRACT FROM AUTHOR]

Lead Sulfide (PbS) nanoparticle-decorated silicon (Si) pyramids array on Si-based photocathodes are fabricated by using pure chemical methods. The PbS thin layers were synthesized by chemical solution deposition onto flat Silicon (Si) and pyramidal textured Silicon (SiPY) obtained from alkaline Si substrate etching. Scanning Electron Microscopy (SEM) was used to carry out the morphological characterization, while UV–Vis-NIR Spectroscopy was used to study the optical properties. The Linear sweep voltammetry (LSV) was conducted to study the catalytic activity in dark and under white light irradiation using a potentiostat station. Cyclic voltammetry in the presence of and without purging CO2 was also investigated. The LSV investigations showed the synergy effect between PbS thin films and Si for the rising and transport of the charge carriers. The results showed a higher photocatalytic towards CO2 reduction of PbS/SiPY compared to Silicon substrate without surface texturization and sensitization. The photoelectrode based on PbS/SiPY could efficiently be used as a photocathode for the photoelectrochemical (PEC) reduction of CO2 to Methanol. [ABSTRACT FROM AUTHOR]

Lead Sulfide (PbS) nanoparticle-decorated silicon (Si) pyramids array on Si-based photocathodes are fabricated by using pure chemical methods. The PbS thin layers were synthesized by chemical solution deposition onto flat Silicon (Si) and pyramidal textured Silicon (SiPY) obtained from alkaline Si substrate etching. Scanning Electron Microscopy (SEM) was used to carry out the morphological characterization, while UV–Vis-NIR Spectroscopy was used to study the optical properties. The Linear sweep voltammetry (LSV) was conducted to study the catalytic activity in dark and under white light irradiation using a potentiostat station. Cyclic voltammetry in the presence of and without purging CO2 was also investigated. The LSV investigations showed the synergy effect between PbS thin films and Si for the rising and transport of the charge carriers. The results showed a higher photocatalytic towards CO2 reduction of PbS/SiPY compared to Silicon substrate without surface texturization and sensitization. The photoelectrode based on PbS/SiPY could efficiently be used as a photocathode for the photoelectrochemical (PEC) reduction of CO2 to Methanol. [ABSTRACT FROM AUTHOR]

The TiO2 thin film, Ag NP and three Ag‐NP/TiO2 composite thin films (COMP‐Agn;n = 20, 50, and 75 Ag mol%) were successfully fabricated on quartz glass. The optical properties of the composite electrodes were investigated, and the results indicate a surface plasmonic resonance peak at 410 nm while the electrical resistivity of the composite thin films improved up to 6.9 × 10−5 Ω cm. The photo‐response threshold of the Ag‐NP/TiO2 composite thin films was enhanced and shifted into the visible and near‐infrared when the chlorophyll dye was adsorbed onto them. The hall effect was performed on the fabricated thin films and the charge carrier concentrate value confirmed that the Ag/TiO2 with Ag concentrate >45% are found to be p‐type. The n‐types were observed till the Ag content in TiO2 was increased up to 45 mol%. COMP‐Ag75 has a charge carrier concentration of 1.3 × 10−19 cm−3 as a p‐type electrode was then employed to construct a p‐DSSC. Such enhancement on photovoltaic activity can be attributed to the generated Z‐scheme system in the anatase/rutile phase‐junction Ag/TiO2 photocathode enhances the separation, diffusion, and transformation of electron/hole pairs inside the structure. This p‐DSSC exhibits a photon‐electrical conversion efficiency (PCE) of 0.37%. The PCE recorded is equal to or greater than those of traditional high‐efficiency n‐DSSCs. This allows the creation of a new generation of photocathodic p‐DSSCs with previously unheard‐of unprecedentedly high concentrations of Ag (up to 80 mol%) evenly scattered in a TiO2 matrix, and this efficacy is the highest ever reported for a p‐type working Ag/TiO2/chlorophyll/iodine electrode. This may enable the use of this electrode as a component of photosensitizer tandem devices. Highlights: ▪The 75 mol% Ag/TiO2 composited higher conductive p‐type electrode was fabricated.▪The Electrode found to have a visible plasmon peak at 410 nm and electrical conductivity of 6.7 × 10−5 cm.▪This p‐type electrode was then employed as a working electrode to construct a p‐DSSC.▪This p‐DSSC exhibits a photon‐electrical conversion efficiency (PCE) of 0.37%.▪Although the PCE is lower, this electrode can be a component of photosensitizer tandem devices. [ABSTRACT FROM AUTHOR]

Hydrogen production from photoelectrochemical (PEC) water splitting has been regarded as a promising way to utilize renewable and endless solar energy. However, semiconductor film grown on photoelectrode suffers from numerous challenges, leading to the poor PEC performance. Herein, a straightforward sol-gel method with the ligand-induced growth strategy was employed to obtain dense and homogeneous copper bismuthate photocathodes for PEC hydrogen evolution reaction. By various characterizations, it was found that the nucleation and surface growth of CuBi2O4 layer induced by 2-methoxyethanol ligand (2-CuBi2O4) demonstrated a decent crystallinity and coverage, as well as a large grain size and a low oxygen vacancy concentration, leading to the good ability of light absorption and carrier migration. Consequently, under simulated sunlight irradiation (AM1.5G, 100 mW/cm2), the 2-CuBi2O4 photocathode achieved an enhanced photocurrent density of −1.34 mA·cm−2 at 0.4 V versus the reversible hydrogen electrode and a promising applied bias photon-to-current efficiency of 0.586%. This surface modification by ligand growth strategy will shed light on the future design of advanced photoelectrodes for PEC water splitting. [ABSTRACT FROM AUTHOR]

Oxide-free surfaces of polycrystalline Cu are prepared using acetic acid etching after chemical-mechanical polishing. UV ozone treatment is shown to increase the work function of the cleaned Cu by up to 0.5 eV. There is also a large reduction in quantum efficiency at 265 nm. Cu sheet can be easily masked from ozone exposure by Si or glass, meaning that selected-area oxi-dation is possible. Oxygen plasma treatment has a similar effect to the UV ozone but is more difficult to mask. There is no increase in surface roughness after oxidation, meaning that the larger work function could significantly re-duce dark current in accelerator photocathodes without affecting the desired photoemission region.

P‐type metal oxides, and in particular NiO, are typically used as hole accepting layers in dye‐sensitized photocathodes. Delafossites (CuMO2) with M=B, Al, Cr or Ga have recently been proposed as attractive substitutes for NiO, with theoretically a higher hole mobility than NiO, therefore allowing a higher efficiency when the photocathode is applied in solar to fuel devices. We have experimentally validated the photoelectrochemical performance of photocathodes consisting of nanoporous CuBO2 (CBO) on Fluorine‐doped Tin Oxide substrates, photosensitized with a light absorbing P1 dye. Femtosecond transient absorption and time‐resolved photoluminescence studies show that light‐induced hole injection occurs from the P1 dye into the CBO in a few ps, comparable to the time constant observed for NiO‐based photocathodes. Importantly, the CBO‐based photocathode shows significantly slower charge recombination than the NiO‐based analogue. These results illustrate the promise of CBO as a p‐type semiconductor in solar energy conversion devices. [ABSTRACT FROM AUTHOR]

The effectiveness of silicon (Si) and silicon-based materials in catalyzing photoelectrochemistry (PEC) CO2 reduction is limited by poor visible light absorption. In this study, we prepared two-dimensional (2D) silicon-based photonic crystals (SiPCs) with circular dielectric pillars arranged in a square array to amplify the absorption of light within the wavelength of approximately 450 nm. By investigating five sets of n + p SiPCs with varying dielectric pillar sizes and periodicity while maintaining consistent filling ratios, our findings showed improved photocurrent densities and a notable shift in product selectivity towards CH4 (around 25% Faradaic Efficiency). Additionally, we integrated platinum nanoparticles, which further enhanced the photocurrent without impacting the enhanced light absorption effect of SiPCs. These results not only validate the crucial role of SiPCs in enhancing light absorption and improving PEC performance but also suggest a promising approach towards efficient and selective PEC CO2 reduction. [ABSTRACT FROM AUTHOR]

The impact of the generation of conduction electrons due to the laser-induced photoelectric effect on the charge dynamics of the semiconductor layer of the photocathode is considered. Qualitative and quantitative agreement between the dependence and the data of a numerical experiment has been achieved. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu2O) has been intensively in the limelight as a promising photocathode material for photoelectrochemical (PEC) water splitting. The state-of-the-art Cu2O photocathode consists of a back contact layer for transporting the holes, an overlayer for accelerating charge separation, a protection layer for prohibiting the photocorrosion, and a hydrogen evolution reaction (HER) catalyst for reducing the overpotential of HER, as well as a Cu2O layer for absorbing sunlight. In this review, the fundamentals and recent research progress on these components of efficient and durable Cu2O photocathodes are analyzed in detail. Furthermore, key strategies on the development of Cu2O photocathodes for the practical PEC water-splitting system are suggested. It provides the specific guidelines on the future research direction for the practical application of a PEC water-splitting system based on Cu2O photocathodes. [ABSTRACT FROM AUTHOR]

The results of calculations of electric fields, potentials, and trajectories of photoelectrons calculations of single-channel dual-spectral thermal imager, implemented in the IIT architecture are presented. The values of the optimal potentials on the control electrodes (microchannel plate, reading electrode, and photocathode) that form a picture of the images of objects and ensure the correct reading of the potential relief from the surface of the sensor-converter pyroelectric film of the image thermal receiver under discussion are determined. [ABSTRACT FROM AUTHOR]

Time-resolved measurements in transmission electron microscopy (TEM) offer the possibility of revealing ultrafast phenomenon with nanometer spatial resolution, allowing the analysis of nonuniform materials, functional materials, and advanced nano-devices. A high-quality pulsed electron beam, with high brightness, narrow energy width, and high spinpolarization, was realized by installing a semiconductor-type photocathode having a negative electron affinity surface to an electron gun in the TEM system. We conducted time-resolved measurements of electron energy-loss spectrum with picosecond pulsed electron beam in the TEM, and elucidated electron-phonon and phonon-phonon relaxation processes in photo-excited gold nanoparticles. Furthermore, the intensity interference of charged fermions was realized by temporally modulated spin-polarized electrons. The coherent spin-polarized electron beam facilitates the extraction of intrinsic quantum interference. These application results pave the way for a new analytical method for the ultrafast dynamics of electrons and lattices in materials, in addition to quantum measurements in electron microscopes. [ABSTRACT FROM AUTHOR]

The possibilities of controlling the structure and type of conductivity of WSe2 films formed on p-type silicon by thermal treatment of a thin-film precursor, which was preliminary obtained using pulsed laser deposition, are studied. Pulsed laser ablation of WSe2 and rhenium targets make it possible to obtain amorphous films WSex (x > 2) containing rhenium atoms and inclusions of β-W nanoparticles. During heat treatment at 450°C, the amorphous matrix crystallization occurs, and a layered shell of 2H-WSe2 is formed around the metal nanoparticles. Doping with rhenium leads to the production of n-type WSe2 semiconductor films, which, in terms of their combination of properties (band gap ~1.2 eV, high catalytic activity, and low resistance to current flow), represent a promising material for creating p-Si photocathodes for efficient light-activated production of hydrogen in an acid solution. Theoretical calculations are carried out, which make it possible to identify local areas of the surface of the formed WSe2 films with enhanced catalytic activity in the reaction of hydrogen evolution. [ABSTRACT FROM AUTHOR]

Abstract Photoelectrochemistry is used to develop solar energy technologies for fuel production and chemical transformations. Semiconductor materials such as TiO2, WO3, BiVO4, Fe2O3, and Cu2O are often investigated in devices designed to convert light energy into chemical energy, including for the production of hydrogen by photoelectrochemical (PEC) water splitting. The oxide electrodes are of significant interest due to their potential for efficient PEC reactions with high durability and their relatively low costs compared to other semiconductor materials. This review highlights the roles played by macroporous photoelectrodes in the development of highly efficient photoelectrodes and advanced PEC systems using polymer electrolytes. Three‐dimensional conductive fiber substrates, such as titanium felt and carbon paper, outperform their two‐dimensional counterparts owing to their larger interfacial areas that enhance PEC properties. The macroporous structures facilitate mass‐transport‐limited reactions when integrated with polymer electrolytes in membrane electrode assemblies. Such configurations are promising for PEC splitting of pure water, and for transforming gaseous molecules such as water vapor, volatile organic compounds, and methane. Optimizing the configuration, including electrode materials selection and ionomer‐coating treatment, can potentially improve the performance of polymer electrolyte membrane PEC cells. Porous transport photoelectrodes integrated with proton/anion‐exchange membranes offer significant opportunities for advanced PEC applications.

A large category of nuclear radiation detection systems are based on scintillation detectors. One of the most important and effective subsystems in performance of scintillation detectors is photomultiplier tube. The photomultiplier tubes with plasmonic photocathodes have higher efficiency and lower dead time compared to the regular tubes. In this research, in order to improve the efficiency and optical response of the photocathode, the plasmonic phenomenon has been used and a new photocathode has been designed and simulated. By periodic circular nanocavities on the surface of aluminum metal, a structure is presented that by making it possible to pair the incoming light to an electron density wave on the surface, plasmonic intensification is created in the desired wavelength range and the field intensity increases greatly. In this way, the quantum efficiency of the photocathode is improved and the detection efficiency is increased up to 15 times compared to the previous cases.

The effectiveness of silicon (Si) and silicon-based materials in catalyzing photoelectrochemistry (PEC) CO2 reduction is limited by poor visible light absorption. In this study, we prepared two-dimensional (2D) silicon-based photonic crystals (SiPCs) with circular dielectric pillars arranged in a square array to amplify the absorption of light within the wavelength of approximately 450 nm. By investigating five sets of n + p SiPCs with varying dielectric pillar sizes and periodicity while maintaining consistent filling ratios, our findings showed improved photocurrent densities and a notable shift in product selectivity towards CH4 (around 25% Faradaic Efficiency). Additionally, we integrated platinum nanoparticles, which further enhanced the photocurrent without impacting the enhanced light absorption effect of SiPCs. These results not only validate the crucial role of SiPCs in enhancing light absorption and improving PEC performance but also suggest a promising approach towards efficient and selective PEC CO2 reduction.

Developing an efficient photocathode system from earth abundant materials is essential for effectual Photoelectrochemical (PEC) water splitting. Charge transfer between heterojunctions is important in fabricating a novel photocathode, keeping cost-effectiveness, abundance, and PEC performance in mind. The p-type narrow band gap photocathode, CuO (Eg = 1.5 eV) synthesized by hydrothermal method, was decorated with Sb2S3 Nanospheres (NSs) by adopting a facile chemical bath deposition (CBD) procedure to fabricate CuO/Sb2S3 NSs heterojunction. Fabricated heterojunction showed better PEC performance contrary to bare CuO, improvement in photocurrent density CuO/Sb2S3 NSs (J = −1 mA cm−2) than CuO (J = −0.3 mA cm−2) photoelectrode at 0 VRHE in 0.5 M Na2SO4 (pH 6.85) is due to enhanced charge carrier generation/separation. The photostability of CuO/Sb2S3 remains intact for 2.5 h with no degradation in photocurrent density. Sb2S3 works as a sensitizer, diminishing the recombination rate of the e−/h+ in CuO/Sb2S3 NSs. UV–Visible and photoluminescence(PL) emission spectra results suggested CuO/Sb2S3 enhanced absorption spectrum and reduced rate of recombination. Electrochemical impedance spectroscopy studies show less charge transfer resistance for CuO/Sb2S3 NSs than CuO. This finding will pave new path in developing novel photocathodic material configurations and heterojunction with Cu-based binary oxides/chalcogenides for solar harvesting.

The structure of a device designed to detect X-ray and optical photons ascending from a sample irradiated with synchrotron radiation or X-ray tube radiation and the principles of its operation are described. The operation of the device consists of determining the delay time of the specified optical photons relative to the X-ray photons. Block diagrams of the main components of the device, outlining the principles of their operation, are given: a monophoton X-ray sensor, a monophoton optical sensor, and a unit for determining the time delay. The areas of scientific and applied use of information obtained with the help of the considered device are indicated. [ABSTRACT FROM AUTHOR]

As the core component of the electron accelerator, the electron source is responsible for providing high-quality electron beams. GaN has a wide bandgap and must be driven by an ultraviolet laser, making it a strong candidate for photocathode electron source research. We established a theoretical model of photoemission for field-assisted negative electron affinity (NEA) AlGaN heterojunction tilted nanowire array photocathodes. The top-down built-in electric field facilitated the transport of photogenerated carriers within the nanowire. The inclination of the nanowires effectively improved the quantum efficiency of the photocathode. With the critical angle of incidence of ultraviolet, the quantum efficiency was up to 81.2%, and the collection efficiency was up to 51%. This work could provide theoretical support for the design and fabrication of high-quality photocathode electron sources.

Surface decoration with cesium on the photocathode is an effective method to reduce surface barriers and promote electron emission. In this study, we investigated the changes in surface properties of AlGaN nanowire coated with Cs atoms using first-principle calculations. The N bridge site is the most stable site for a single atom deposition. As more Cs atoms are deposited on the surface, the average adsorption energy increases along with the weakened ionization of Cs adatoms. The Bader charge of surface Al and Ga atoms undertake significant changes in comparison with tiny alteration of N atoms, especially for Al atom with a decrease of 0.41 |e|/atom. The variation in surface work function reaches a maximum of 2.3 ∼ 2.5 eV at Cs coverage of 0.5 ∼ 0.75 ML, which can be attributed to the synergistic effect of dipole length and charge redistribution. The donor states underneath CBM induced by the orbital overlap of Al-p, Ga-p and Cs-d electrons accompanied by the downward band bending in the band structures. This work provides theoretical insight into the surface evolution of Cs-decorated AlGaN nanowires and offers guidance for the development of state-of-the-art nanostructured vacuum devices.

Visible‐light‐driven semiconductor photoelectrodes are promising new devices for on‐demand photocathodic generation of hydrogen peroxide. Herein, the fabrication of organic polymeric photocathodes employing poly(4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole) (pThBTD), and comparatively seven other related derivatives is reported. The monomer dithienobenzodithiazole can be directly polymerized on an electrode via two methods: electropolymerization or iodine‐vapor‐assisted polymerization. Both give polymers with wide visible light absorption and suitable stability for photoelectrodes. These methods yield different active layer morphologies, with electropolymerization yielding photocathodes with better performance. Critical issues affecting oxygen reduction photocurrents are evaluated, namely thickness, wettability, and pH. Photocathodic oxygen reduction currents, as well as photovoltages, are among the highest reported for an organic photoelectrocatalyst, and pThBTD films can stably produce H2O2 with high faradaic yield over at least 8 h. This study shows that single‐component organic semiconductor devices can be highly competitive versus more complex heterostructures and that such low‐bandgap organic polymers can afford remarkable stability. [ABSTRACT FROM AUTHOR]

Converting solar energy into hydrogen by photo‐electrochemical cells is believed to be one of the most promising strategies to acquire clean energy. However, one barricade for further improving the performance of the photocathode system is flattening of the Schottky barrier formed at the interface between the p‐type photo‐absorber and metal co‐catalyst (e. g. Pt/p‐Si) due to the mismatch of their Fermi levels. Here, we present a facile way of making photocathodes by transferring high‐quality chemical vapor deposition (CVD) graphene onto p‐type Si as a buffer layer, which can effectively diminish the Pt/p‐Si interfacial barrier and promote charge separation efficiency, hence, improving the photo‐electrochemical performance of such a device for hydrogen generation. The measured photocurrent density is 3.9 times higher than that achieved without graphene buffer. This approach offers a novel route to decrease the Pt/p‐Si interfacial barrier for developing highly efficient solar conversion systems in the future. It can easily be extended to many other photocathode systems. [ABSTRACT FROM AUTHOR]

One of the promising methods to solve the current energy and environment issues is photoelectrochemical (PEC) water splitting and CO2 reduction reaction. Chalcopyrite copper indium gallium sulfide (CIGS) and CuIn0.3Ga0.7S2 nanocrystal thin films have been considered photovoltaic materials, and here, we demonstrated their potential to reduce CO2 into CO. A modified solution process affords to decrease the number of surface ligands, which triggers an increase in the crystal size and an improved reproducibility in performance and output current. After depositing gold nanoparticles on the surface of CIGS, the Faradic efficiency related to the CO2-to-CO conversion can reach 12.93% in aqueous electrolytes and 25% in nonaqueous electrolytes. Further investigation points out that in the range of applied potential between −0.1 and −0.2 V vs a reversible hydrogen electrode (RHE), the CIGS photocathode appears to display a stable photocurrent density for 1 h, but when applying a higher applied bias, such as of −0.3 V vs RHE, the degradation of the current is significant. Additionally, we found that coupling catalysts to the CIGS increases the selectivity toward CO and minimizes the competitive hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

High-efficiency photoelectrode played a significant role in photocatalytic fuel cell (PFC) systems. In this study, a zinc-based metal-organic framework modified by carbon quantum dots (N-Zn-MOF/CQDs) and the BiVO 4 were respectively presented as the photocathode and photoanode of the PFC system toward Cr(Ⅵ) reduction. Various analytical techniques were utilized to characterize the physicochemical, optical and photoelectrochemical properties of the as-prepared samples. With the addition of CQDs, the visible-light response and charge separation rate were remarkably enhanced. In the PFC system, the circuit current density of 58.04 mA cm−2 and max power density of 1.35 mW cm−2 were achieved, which was superior to other reported PFC systems. Under optimized conditions, 100% Cr(Ⅵ) can be removed within 120 min of visible-light illumination. This work provided a new method to decorate the zinc-based metal−organic framework cathode to dramatically improve the photocatalytic performance. • A novel N-Zn-MOF/CQDs photocathode was successfully constructed. • The introduction of CQDs enhanced visible-light response and charge separation rate. • The photocatalytic fuel cell was built with the fabricated N-Zn-MOF/CQDs. • The PFC showed higher power density and removal efficiency for Cr(VI). [ABSTRACT FROM AUTHOR]

Cu (OH)2 nanowire arrays were grown on the surface of copper sheets by electrochemical method, annealed under nitrogen atmosphere to obtain Cu2O nanowire arrays, and then Cu2O/CeO2 heterojunction photocathode materials were prepared by depositing Cu2O blocking layer and CeO2 on the electrode by electrodeposition method. The material is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for its morphology and chemical composition, and by ultraviolet-visible absorption spectroscopy (UV-Vis), linear scanning voltammetry (LSV) and Mott-Schottky plot (M-S) for its photoelectrochemical properties. The results of the experimental data show that the photocurrent density of the Cu2O/CeO2 photocathode reaches-6.55 mA/cm² at 0V vs. RHE（reversible hydrogen electrode), which is 1.78 times higher than that of Cu2O (-3.67 mA/cm²). Subsequently, TiO2 was prepared by ALD (atomic layer deposition) as a protective layer and loaded with Pt as a co-catalyst for the hydrogen evolution reaction (HER) . The final photocurrent density of the Cu2O/CeO2/TiO2/Pt photocathode reached-10.9 mA/cm² and the applied bias photon-to-current conversion efficiency (ABPE) reached 2.02%. The results of the experiments are of great importance for the wide application of Cu2O-based photocathode materials in the field of photoelectrochemical water splitting. [ABSTRACT FROM AUTHOR]

This work discusses the influence of different cleaning procedures on p‐gallium nitride (GaN) grown on sapphire by metal–organic chemical vapor deposition. The cleaned p‐GaN surface was transferred into an ultrahigh vacuum chamber and studied by an X‐ray photoelectron spectrometer, revealing that a cleaning with a so‐called "piranha" procedure results in low carbon and oxygen concentrations on the p‐GaN surface. Contrary, a cleaning that solely uses ethanol represents a simple cleaning but leads to an increase of carbon and oxygen contaminations on the surface. Afterward, the cleaned p‐GaN samples underwent a subsequential vacuum thermal cleaning at various temperatures to achieve an atomically clean surface. X‐ray photoelectron spectroscopy (XPS) measurements revealed residual oxygen and carbon on the p‐GaN surface. Thus, a thermal treatment under a vacuum did not entirely remove these organic contaminations, although the thermal cleaning reduced their peak intensities. The complete removal of carbon and oxygen contaminants was only achieved by argon ion sputtering, which is accompanied by a strong depletion of the nitrogen on the p‐GaN surface. The treatments cause a large number of surface defects preventing the formation of a negative electron surface when the p‐GaN is activated with a thin layer of cesium. [ABSTRACT FROM AUTHOR]