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Neodymium and ytterbium sulphide transparent photoactive electrode was fabricated through the spin coating technique for a photoelectrochemical cell. The photoelectrode's optical and electrical responses were studied along with its crystal structure and elemental makeup. In composite, NdYbS 3 was found using X-ray diffraction analysis, and compact structures were found utilising SEM examination. The composite contained neodymium, ytterbium, and sulfur, as determined by EDX and XPS. Tauc's figure was used to establish the optical band gap. Fourier transform infrared spectroscopy was employed to analyze and identify distinctive functional groups present in the sample. Photoelectrochemical properties of the electrode were investigated by applying several electrochemical techniques in a three electrode photocell system. The photocurrent density exhibited by the electrode was consistently higher compared to its performance under dark conditions, according to every experiment. The specific capacitance of the photo-electrode amplified at all sweep speeds in the presence of illumination. Under illumination, the highest specific capacitance was found to be 851 Fg-1 in comparison to 787 Fg-1 when there was no light source. It can be presented that a practical photo-electrode that can be engaged in sustainable energy arrangements has been introduced by this work. [ABSTRACT FROM AUTHOR]

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

Biochar has been obtained by pyrolysis of spent malt rootlets under limited oxygen supply and further activated by mixing with KOH and pyrolyzed again at high temperature. The total specific surface area of such activated biochar was 1148 m2 g−1, while that of micropores was 690 m2 g−1. This biochar was used to make a functional electrode by deposition on carbon cloth and was combined with a photoelectrochemical cell. The biochar electrode functioned as a supercapacitor in combination with the electrolyte of the cell, reaching a specific capacity of 98 Fg−1, and it was capable of storing charges generated by the cell, proving current flow both under illumination and in the dark. The same electrode could be used as an air-cathode providing oxygen reduction functionality and thus demonstrating interesting electrocatalyst properties. [ABSTRACT FROM AUTHOR]

Efficient charge transfer between organic semiconductors and electrode materials at electrode interfaces is essential for achieving high-performance organic optoelectronic devices. For efficient charge injection and extraction at the electrode interface, an interlayer is usually introduced between the organic active layer and electrode. Here, a simple and effective approach for further improving charge transfer at the organic active layer–interlayer interface was presented. Treatment of the zinc oxide (ZnO) interlayer, a commonly used n-type interlayer, with a fullerene-based self-assembled monolayer (SAM) effectively improved electron transfer at the organic–ZnO interface, without affecting the morphology and crystalline structure of the organic active layer on the cathode interlayer. Furthermore, this treatment reduced charge recombination in the device, attributed to the improved charge extraction and reduction of undesirable ZnO-donor polymer contacts. The photocurrent density and power conversion efficiency of organic solar cells employing the fullerene-SAM-treated interlayer were ~10% higher than those of the device employing the nontreated interlayer. This improvement arises from the enhanced electron extraction and reduced charge recombination. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) has been widely applied as a photoelectrode material. Its poor charge separation properties and utilization efficiency have been the major obstacles in its application to photoelectrochemical (PEC) water oxidation. Herein, a highly-efficient FeOOH/Y-BiVO4 photoelectrode was designed to overcome the limitations of pure BiVO4. The FeOOH/1%Y-BiVO4 photoelectrode shows an optimal photocurrent density of 3.84 mA cm−2 at 1.23 V vs. RHE, which is 1.3 times greater than a pure BiVO4 photoelectrode (0.93 mA cm−2). The photocurrent density enhancement is attributed to the promoting effects of Y-doping and the loading of FeOOH on the electrode surface, which improve the light responsiveness, charge separation and charge transfer efficiency of BiVO4. Furthermore, the composite electrode also exhibited efficient PEC degradation of tetracycline hydrochloride. The results of this work indicate that elemental doping and cocatalyst loading can be utilized to fabricate an efficient BiVO4 electrode for solar water oxidation and wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) usually shows a low photoelectrochemical (PEC) performance due to its poor conductivity. To improve the transfer of charge carriers generated by g-C3N4, a TiO2/g-C3N4 composite photoanode was prepared by a facile co-electrodeposition method. The composite photoelectrodes exhibit an improved PEC performance compared to TiO2 and g-C3N4. The PEC performance was optimized by varying the mass ratio of TiO2 to g-C3N4, and a ratio of 1:1 gave the best photocurrent density of 1.81 mA cm−2, which is 2.27 times larger than that of the pure TiO2 photoanode under full-arc xenon light. Furthermore, compared with pure g-C3N4, the photocurrent density is greatly improved. The incident photocurrent efficiency reached 4.14% under irradiation with 365 nm monochromatic light. TiO2/g-C3N4 exhibits a stable photocurrent density in a PEC reaction over 2 h. The enhanced PEC performance is attributed to the synergism between TiO2 and g-C3N4 semiconductors, which improves the interfacial charge transfer and inhibits the photogenerated electron–hole pair recombination. [ABSTRACT FROM AUTHOR]

In this research, TiO2/MoS2 nanocomposite electrodes were synthesized to investigate the photoelectrochemical performances. Firstly, TiO2 nanotubes were fabricated by anodic oxidation on Ti foil. Then, MoS2 nanostructures were synthesis by hydrothermal method on TiO2 nanotubes. The prepared nanocomposite films were characterized by using X-Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The transient photocurrent response was analyzed to investigate photoelectrochemical activity of electrodes. The results show that TiO2 nanotube arrays coated with MoS2 nanostructure homogeneously. Furthermore, TiO2/MoS2 nanocomposite electrode were shown better photoelectrochemical activity then bare TiO2 electrode. [ABSTRACT FROM AUTHOR]

Solar‐assisted photoelectrochemical (PEC) water splitting to produce hydrogen energy is considered the most promising solution for clean, green, and renewable sources of energy. For scaled production of hydrogen and oxygen, highly active, robust, and cost‐effective PEC electrodes are required. However, most of the available semiconductors as a PEC electrodes have poor light absorption, material degradation, charge separation, and transportability, which result in very low efficiency for photo‐water splitting. Generally, a promising photoelectrode is obtained when the surface of the semiconductor is modified/decorated with a suitable co‐catalyst because it increases the light absorbance spectrum and prevents electron–hole recombination during photoelectrode reactions. In this regard, numerous p‐ and d‐block elements, single atoms, and graphene‐based PEC electrodes have been widely used as semiconductor/co‐catalyst junctions to boost the performances of PEC overall water splitting. This review enumerates the recent progress and applications of p‐ and d‐block elements, single atoms, and graphene‐based PEC electrodes for water splitting. The focus is placed on fundamental mechanism, efficiency, cells design, and various aspects that contribute to the large‐scale prototype device. Finally, future perspectives, summary, challenges, and outlook for improving the activity of PEC photoelectrodes toward whole‐cell water splitting are addressed. [ABSTRACT FROM AUTHOR]

A hierarchical electrode consisting of a Ni foam substrate, an intermediate layer of a Mo-doped basic cobalt carbonate microwire array, and a surface layer of NiCoP was fabricated for hydrogen evolution. The introduction of the intermediate layer accounted for the low overpotential (45 mV, 10 mA cm−2) and high solar-to-hydrogen conversion efficiency (14.9%) in a PEC water splitting application. [ABSTRACT FROM AUTHOR]

Niobium-based oxide semiconductors face the problems of narrow photo-response range and fast carrier recombination in the field of photoelectrochemical (PEC) water splitting. Based on the above problems, we chose the idea of constructing a heterojunction and successfully loaded Ag 2 O onto Nb 2 O 5 photoanode by ion precipitation to effectively enhance the carrier separation efficiency and broaden its photo-response range. The results show that the composite electrode NA-3 exhibits excellent photoelectrocatalysis performance under illumination and bias voltage. The photocurrent density was increased to 0.481 mA/cm2, approximately 2.88 times that of the Nb 2 O 5 photoanode, and a negative onset potential shift of 139 mV was achieved. The higher ABPE and IPCE values of composite electrode indicate its higher catalytic conversion ability and quantum efficiency. The Mott-Schottky results reveal that the loading of Ag 2 O not only causes a negative shift of V fb , improves Faraday transfer efficiency, but also reduces W Dep at the electrode/electrolyte interface, effectively improving the photocatalytic performance of the photoanode. This work promotes the development of Nb 2 O 5 materials in the field of PEC water splitting through the idea of constructing heterojunctions, and provides an effective strategy for suppressing carrier recombination to achieve highly active photoanodes. [Display omitted] • Constructing heterogeneous structure to improve the redox ability of Nb 2 O 5 photoanode. • The Ag 2 O loading suppressed the photogenerated carrier recombination and optimizing the OER reaction. • The composite electrode Nb 2 O 5 /Ag 2 O exhibits excellent photoelectrocatalysis performance. [ABSTRACT FROM AUTHOR]

Cu2O/gas diffusion layer (GDL) electrodes prepared by electrodeposition were studied for the electrocatalytic reduction of CO2. The designed electrode was also tested in solar‐light‐induced CO2 conversion in combination with a CuO/NtTiO2 photoanode using a compact photoelectrocatalytic (PEC) cell. Both PEC cell electrodes were prepared using non‐critical raw materials and low cost, easily scalable procedures. In the PEC experiments, a total carbon faradaic selectivity of about 90 % to formate and about 75 % to acetate was obtained after 24 h of operations without application of potential/current or using sacrificial agents. In electrocatalytic tests of CO2 reduction at −1.5 V, the same electrode yielded high total faradaic selectivity (>95 %) but formed selectively formate (about 80 % selectivity) rather than acetate. The in situ transformation of the Cu2O/GDL electrode leads to the formation of a hybrid Cu2O–Cu/GDL system. Cyclic voltammetry data indicate that the potential and the presence of CO2 (not only of HCO3− species) are both important elements in this transformation. Data also indicate that the surface concentration of CO2 (or of its products of transformation) on the electrode is an important factor to determine performance in the conversion of CO2. [ABSTRACT FROM AUTHOR]

• A n–p heterojunction type photoanode composed with CuWO4 and Mn3O4 was synthesized. • The composite demonstrates the enhanced light harvesting, PEC performances and electron-hole separation. • H 2 and O 2 were successfully collected separately from each electrode in PEC cell. In this paper, we report a novel photoanode fabricated by spin-coating n-type CuWO 4 nano-ovoids on the surface of fluorine-doped tin oxide (FTO) glass and then modified with p-type Mn 3 O 4 nanospheres using a deposition-annealing method. A novel nanocomposite (CuWO 4 /Mn 3 O 4) with p/n heterojunction formed on the surface of FTO glass. The characterazation results of the nanocomposite indicate that the two moieties of the nanocomposite intimately contact with each other. The photoelectrochemical tests of the prepared CuWO 4 /Mn 3 O 4 photoanode reveal that the electrode can produce larger anodic photocurrent and show enhanced incident photon-to-current efficiency (IPCE) than the bare CuWO 4 photoanode does. Moreover, the PEC tandem cell assembled by using the CuWO 4 /Mn 3 O 4 electrode as photoanode and Pt plate as counter electrode demonstrates enhanced photocatalytic activity and stability for photoeletrochemical (PEC) water splitting. The amount of hydrogen and oxygen, collected from the counter chamber and the photoanode chamber, separately, reached to 5.0 μmol and 2.3 μmol, respectively, under 2 h simulated sunlight irradiation at 1.20V vs. RHE bias without any sacrificial agent. The remarkable performance of the nanocomposite anode owe to the formed heterojunction structure in the nanocomposite, leading to high photoexcited charge transfer and separation. [ABSTRACT FROM AUTHOR]

In this paper, nano-CuO films, fabricated using the simple "doctor blade" technique, are studied as photoelectrodes in a two-electrode PEC cell for water photolysis. SEM analysis confirm the nanometric size of film grains and the photoelectrode porosity. The photocurrent behavior is studied, particularly, photocurrent transients for non-assisted and assisted water photolysis. Existing defects acting as carrier traps explain the different transient behaviors found. The existence of defects is explored using X-ray diffraction technique and the Williamson-Hall method. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride materials (CNs) have emerged as suitable photocatalysts and heterogeneous catalysts for various reactions thanks to their tunable band gap, suitable energy‐band position, high stability under harsh chemical conditions, and low cost. However, the utilization of CN in photoelectrochemical (PEC) and photoelectronic devices is still at an early stage owing to the difficulties in depositing high‐quality and homogenous CN layer on substrates, its wide band gap, poor charge‐separation efficiency, and low electronic conductivity. In this Minireview, we discuss the synthetic pathways for the preparation of various structures of CN on substrates and their underlying photophysical properties and current photoelectrochemical performance. The main challenges for CN incorporation into PEC cell are described, together with possible routes to overcome the standing limitations toward the integration of CN materials in PEC and other photoelectronic devices. [ABSTRACT FROM AUTHOR]

Ta3N5 nanotubes (NTs) were obtained from nitridation of Ta2O5 NTs, which were grown directly on Ta foil through a 2-step anodization procedure. With Co(OH)x decoration, a photocurrent density as high as 2.3 mA cm−2 (1.23 V vs. NHE) was reached under AM1.5G simulated solar light; however, the electrode suffered from photocorrosion. More stable photoelectrochemical (PEC) performance was achieved by first loading Co(OH)x, followed by loading cobalt phosphate (Co–Pi) as double co-catalysts. The Co(OH)x/Co–Pi double co-catalysts may act as a hole storage layer that slows down the photocorrosion caused by the accumulated holes on the surface of the electrode. A “waggling” appearance close to the “mouth” of Ta2O5 NTs was observed, and may indicate structural instability of the “mouth” region, which breaks into segments after nitridation and forms a top layer of broken Ta3N5 NTs. A unique mesoporous structure of the walls of the Ta3N5 NTs, which is reported here the first time, is also a result of the nitridation process. We believe that the mesoporous structure makes it difficult for the nanotubes to be fully covered by the co-catalyst layer, hence rationalizing the remaining degradation by photocorrosion. [ABSTRACT FROM AUTHOR]

Abstract In this work, a photoactive material, Graphdiyne (GDY) loaded with AuNPs (AuNPs-GDY), was successfully synthesized. The fabricated material made use of the natural band-gap structure of GDY, which could produce hole-electron pairs and the plasmon resonance effect of AuNPs to obtain a high photoelectrochemical (PEC) response. AuNPs-GDY PEC response changed with the mass ratio of GDY to tetrachloroauric acid. When the mass ratio of GDY to tetrachloroauric acid was 1:2.5, AuNPs-GDY exhibited the best PEC performance. Thus, the best one was selected as the photoactive material to establish a PEC biosensor for microRNA detection. The PEC biosensor used the alkaline phosphatases as catalyzer to generate ascorbic acid in situ, which provided a low background signal and a high PEC response. The cancer marker, MicroRNA let-7a, was chosen as a target model. Under optimal condition, potential 300 mV and pH 8.0, the PEC biosensor had a detection limit of 3.3 × 10–19 M and a good linearity with microRNA let-7a concentration ranged from 1.0 × 10–18 M to 1.0 × 10−10 M. This PEC biosensor opened a promising platform using GDY to fabricate analytical method and detect microRNA at ultralow levels for diagnoses. Highlights • A novel material, AuNPs-GDY, was firstly synthesized. • SPR effect caused by the AuNPs played a key role in enhancing PEC signals. • A PEC biosensor based on AuNPs-GDY for the let-7a microRNA detection. • The detection limit of 3.3 × 10−19 M was achieved. [ABSTRACT FROM AUTHOR]

Photoelectrochemical cell composed of solution-processed nanoflower heterostructure of Au core and eight CdSe petals was investigated for enhanced photocurrent generation. The electrode of CdSe nanorods displayed photocurrent density of 2.1 mA/cm2 whereas the Au core CdSe nanoflower exhibited 4.6 mA/cm2 corresponding to a 119% increase during photoelectrochemical cell performance. Both electrodes showed prompt response to the on/off cycles of light, the photocurrent gain (IPhoton/Idark) in CdSe nanorods is 124.7, while the value is 223.3 for Au/CdSe nanoflower, calculated from the growth-decay curves. Photoresponse time was dramatically improved for Au/CdSe nanoflower samples due to increasing in 66% incident photon-to-current emission. Electron lifetime of 21.63 and 48.71 ns was observed for the electrode of CdSe nanorods and Au/CdSe nanoflowers respectively. The prolonged electron lifetime in the case of the electrode of Au/CdSe nanoflowers was responsible for improving charge separation and as a consequence, higher photocurrent generation. [ABSTRACT FROM AUTHOR]

Abstract The novel photoelectrochemical cell with very high photocurrent density (>35 mA/cm2) is demonstrated by nanoscale architecturing of TiO 2 /CdS/CdSe multi-core-shell nanorods. While dimensions of constituting layers, i.e. TiO 2 nanorod templates, CdS, and CdSe shell layers, are optimized by thorough investigation of optical and photoelectrochemical responses of each layer, high light absorption through the nanorod geometry and facile transport of the photo-generated electrons and holes along the high conduction path of CdSe and CdS result in the high photoelectrochemical performances. In addition, the microscopic model for the electron and hole transport in the core-shell nanorod is elaborated using the energy band diagram. The demonstration of the high performance PEC electrode as well as the platform to optimize PEC electrodes are highlighted in the current work. Graphical abstract Image 1 Highlights • Design of the TiO 2 /CdS/CdSe double-sheath core-shell nanorod array. • Superior photoelectrochemical properties (high photocurrent density). • Fundamental understanding about the charge transport mechanism of the core-shell nanorod. [ABSTRACT FROM AUTHOR]

Composite Ti/TiO2/Cu2O electrodes were produced by electrodeposition of p-Cu2O nanoparticles over the surface of TiO2 nanotubes generated by one-step electrochemical anodization of titanium. The effect of electrodeposition potential and duration of the electrodeposition experiments on size and morphology of the Cu2O nanoparticles was evaluated by FE-SEM analysis. In order to evaluate the photo-catalytic activity of the composite electrodes, photo-degradation experiments with methylene blue and photo-electrochemical tests were performed. An anodic current was generated by photo-electrochemical tests under visible light and zero bias, confirming the transfer of photo-generated electrons from Cu2O to TiO2. However, in both the photodegradation and the photo-electrochemical experiments, the photo-catalytic activity of the composite electrodes under simulated solar irradiation (UV + visible) was lower as compared to the application of the bare TiO2 nanotubes electrodes. The mechanisms that could justify such results are thoroughly discussed. [ABSTRACT FROM AUTHOR]

In photoelectrochemical (PEC) water oxidation, a low onset potential and a high photocurrent are desired and a cocatalyst on the photoanode could improve the performance. For better use of a NiFe layered double hydroxide (LDH) cocatalyst, concept of exfoliation is applied. Exfoliation gives higher electrochemical surface area and better water oxidation kinetics, which is reflected in improved charge injection efficiency at low bias potentials. Exfoliated NiFe LDH shows increased photocurrent density by 50 % at 1.0 VRHE and reduced onset potential by 140 mV relative to those of stacked bulk LDH under 1 sun illumination, making it a much more effective cocatalyst for α‐Fe2O3 photoanode. The intensity modulated photocurrent spectroscopy shows that the improved photocurrents and early onset potentials of exfLDH/α‐Fe2O3 photoanode are attributed to fast charge transfer and, more importantly, suppressed charge recombination due to passivation of α‐Fe2O3 surface by the LDH monolayer sheet. Double trouble catalysis: Exfoliated NiFe LDH accelerates photoelectrochemical water splitting as a cocatalyst for α‐Fe2O3 more effectively than stacked LDH in terms of onset potential and photocurrent generation. The effects originate from fast charge transfer and suppressed charge recombination due to passivation of α‐Fe2O3 surface by LDH monolayer sheet. [ABSTRACT FROM AUTHOR]

A pn junction based on the black Si wafer has been prepared for the photoelectrochemical (PEC) applications by a facile chemical etching method combined with thermal diffusion process. And also in this work, a black Si wafer were fabricated by using a commercial multicrystaline Si (mc-Si) wafer as the raw. It was demonstrated that pn junction was beneficial to enhance the PEC performance of a Si photoanode. The mechanism was further clarified by an electrochemical impedance analysis. The improved PEC activity was attributed to a more efficient charge separation inside the solid electrode. Besides, the p-type Si wafer displayed a characteristic of n-type semiconductor, which was explained through a simple energy band model. [ABSTRACT FROM AUTHOR]

Abstract The photoelectrochemical electrode has been intensively studied in recent years as a means of generating electricity from light through the use of intact thylakoid membranes or highly purified photosystem II. PSII-enriched thylakoid membrane fragments (PSII-BBY), also have the potential to construct the photoelectrochemical anode. In this study, we examined the feasibility of utilizing PSII-BBY preparations to construct a relatively inexpensive photoelectrochemical anode with a comparable current density and a reasonable stability. Intact thylakoid membrane based photoelectrochemical electrode was also constructed to compare with the PSII-BBY based photoelectrochemical electrode with respect to the protein activity and current density. In addition, the practicability of replacing the popular gold nanoparticle modified gold slide with multi-walled carbon nanotube modified indium tin oxide coated slides was tested. In order to understand the surface change during slide surface modification, an atomic force microscope (AFM) was used to image the topography of the slide. Above all, we observed a current density of 20.44 ± 1.58 μA/cm2 when PSII-BBY was used to construct the photoelectrochemical anode. Moreover, the PSII-BBY based photoelectrochemical anode showed high stability over time with the current decreasing at a rate of 0.78%/h. Highlights • Thylakoid, multi-walled carbon nanotubes, and indium tin oxide coated glass used • The photoelectrochemical probe showed high current density of 20.44 ± 1.58 μA/cm2. • Current density decreased by 0.78%/h over 20+ min of continuous testing. [ABSTRACT FROM AUTHOR]

A plasmonic WO 3 /Au photocatalyst was successfully synthesized by a reversible charging and discharging mechanism. The photocatalyst showed much higher photocatalytic activity and photoelectrochemical (PEC) performance than pure WO 3 , due to the localized surface plasmonic resonance (LSPR) enhancement of Au nanoparticles (Au NPs). In addition, Au NPs also could enhance the absorption of visible light and suppress the recombination of photogenerated electron-hole pairs. Hg 2+ ions could make the effects of Au NPs weak through forming amalgam with Au at WO 3 /Au surface, thus the photocurrent response of the resulting WO 3 /Au/ITO electrode decreased. Hence, the electrode could be used for the selective detection of Hg 2+ although no special recognition element was introduced. The wide linear range of 4.2 pM‒840 pM and quite low detection limit of 2.0 pM made it suitable for the detection of ultra-micro Hg 2+ in real samples. Thus, the WO 3 /Au based PEC sensor had active effect on solving some tough issues, such as complicated operation and rigorous measurement conditions, in the detection of ultra-micro Hg 2+ . [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The bio-catalyst, hydrogenase, has been immobilized on a ZnO protected Cu 2 O photoelectrode for the first time, showing light driven hydrogen generation in a photoelectrochemical cell. • The strong binding between hydrogenase and ZnO has been proved in solution system as well as on the electrode. • The formation of nano-sticks between ZnO and hydrogenase under light illumination has been monitored. Abstract A Cu 2 O-ZnO-hydrogenase photocathode possessed enzyme/semiconductor junction has been constructed by immobilizing a biological protein catalyst, hydrogenase-CrHydA1 enzyme on the ZnO protected Cu 2 O electrode. With light illumination, a photocurrent of 0.8 mA/cm2 at 0.15 V vs. RHE was obtained and hydrogen was successfully detected from the photocathode in photoelectrochemical measurements with Faradaic efficiency of ca. 1%. The construction as well as the stability of the system are also reported. The result shows that this biohybrid photocathode is capable of photocatalytic proton reduction under mild conditions. [ABSTRACT FROM AUTHOR]

The pyrite iron disulfide thin films are regarded as suitable candidates for construction of low-cost photoelectrochemical (PEC) solar cells. Iron oxide hematite has attracted much attention as possibly convenient material for hydrogen production via PEC water splitting. We refer on preparation of pyrite thin films via thermal sulfidation of hematite films synthetized by a physical methodology of high power impulse magnetron sputtering (HiPIMS) and purely chemical approach of sol-gel. We studied for the first time the correlation between PEC functionality of hematite films and after their sulfidation into pyrite. The highest PEC activity of hematite films of 560 μA cm −2 at 700 mV vs. Ag/AgCl was achieved with the HiPIMS photoelectrodes. The photoefficiency dropped dramatically to 4 μA cm −2 at 600 mV vs. Ag/AgCl after the sulfidation. A significant increase of grains‘ size, residual unreacted hematite, surface defects were the main reasons for the poor photoactivity. The sol-gel produced hematite yielded photocurrent of 30 μA cm −2 and a slight increase to 40 μA cm −2 (recorded at 500 mV vs. Ag/AgCl) of the corresponding pyrite version. Both these electrodes showed also similar morphological characteristics. The structural, electronic and optical properties of the deposited films were determined using various methods e.g. Raman spectroscopy, SEM, and PDS. [ABSTRACT FROM AUTHOR]

Strontium titanate (STO) is an oxide that has found application in several technological areas and is a candidate electrode for photoelectrochemical cells (PECs). In this study, STO thin films were prepared via pulsed laser deposition to function as PEC electrodes. Effects of post-deposition annealing in a reducing environment on the photocatalytic activity of these electrodes are characterized by measurements of optical and electrochemical properties of the films. These observations are used to obtain insight into how the crystal and electronic properties of these electrodes are affected by the annealing process. Low annealing temperatures produce non-crystalline STO films that exhibit low photocatalytic activity. Annealing at 500 °C and higher allowed the formation of crystalline STO, which showed substantially higher ultraviolet-driven photocurrent densities. Electrochemical impedance spectroscopy reveals large decreases in charge transfer resistance that is associated with improved performance of these films. Oxygen evolution at these electrodes was confirmed with a rotating ring-disk electrode setup. Porous versions of the STO films were investigated to evaluate the effect larger surface area can have in enhancing the water oxidation performance. [ABSTRACT FROM AUTHOR]

In this study, we describe the design and operation of a temperature-controlled photoelectrochemical cell for analysis of gaseous and liquid products formed at an illuminated working electrode. This cell is specifically designed to quantitatively analyze photoelectrochemical processes that yield multiple gas and liquid products at low current densities and exhibit limiting reactant concentrations that prevent these processes from being studied in traditional single chamber electrolytic cells. The geometry of the cell presented in this paper enables front-illumination of the photoelectrode and maximizes the electrode surface area to electrolyte volume ratio to increase liquid product concentration and hence enhances ex situ spectroscopic sensitivity toward them. Gas is bubbled through the electrolyte in the working electrode chamber during operation to maintain a saturated reactant concentration and to continuously mix the electrolyte. Gaseous products are detected by an in-line gas chromatograph, and liquid products are analyzed ex situ by nuclear magnetic resonance. Cell performance was validated by examining carbon dioxide reduction on a silver foil electrode, showing comparable results both to those reported in the literature and identical experiments performed in a standard parallel-electrode electrochemical cell. To demonstrate a photoelectrochemical application of the cell, CO2 reduction experiments were carried out on a plasmonic nanostructured silver photocathode and showed different product distributions under dark and illuminated conditions. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis of cuprous oxide (Cu 2 O) nanoparticles modified vertically oriented aligned titanium dioxide (TiO 2 ) nanotube arrays through wet chemical treatment of TiO 2 nanotubes and their multi-functional application as enhanced photo electrochemical and hydrogen generation. The synthesized samples were characterized by X-ray diffraction, SEM, TEM, and UV–Vis spectroscopy. The structural characterization revealed that the admixed Cu 2 O nanoparticles on the TiO 2 surface did not alter its crystalline structure of vertically oriented aligned TiO 2 nanotube. The photocatalytic performance and hydrogen generation of as synthesized Cu 2 O nanoparticles modified aligned TiO 2 nanotube was found to highly depend on the Cu 2 O content. The optical characterizations reveal that the presence of Cu 2 O nanoparticles extends its absorption into the visible region which improves the photocurrent density in comparison to pristine aligned TiO 2 nanotubes electrodes due to enhanced photoactivity and better charge separation. The optimum photocurrent density and hydrogen generation rate has been found to be 3.4 mA cm −2 and 127.5 μmole cm −2 h −1 in 1 M Na 2 SO 4 electrolyte solution under 1.5 AM solar irradiance of white light with illumination intensity of 100 mW cm −2 . [ABSTRACT FROM AUTHOR]

Electrospun tungsten oxide/nickel tungstate (WO/NiWO) composite nanofibers were tested for photoelectrochemical (PEC) performance under visible light irradiation under three voltages, 1.6, 1.8 and 2.0 V with reference to Ag/AgCl electrode in 0.5 M HSO. It was found that the photocurrent density of this novel nanostructure fiber is about 70% higher than the pristine electrospun WO fibers under similar conditions. WO/NiWO heterojunction was identified within the fiber through high-resolution transmission electron microscopy imaging. The fibrous form is expected to provide greater exposure to the WO/NiWO heterojunctions for the photocatalytic reaction. This heterojunction within the fibrous form is expected to provide a higher photoanode performance due to a lower charge-transfer resistance than the pristine WO fibers as also confirmed through the electrochemical impedance spectra. Interestingly, calcination of these composite fibers at 800 °C instead at 550 °C increased the percentage of NiWO phase, yet with a contemporaneous increase in larger crystallites of metal tungstate. The latter was responsible for giving lower photocurrents which helped in understanding the PEC performance with respect to material structure for the composite fiber under the current study. [ABSTRACT FROM AUTHOR]

Gallium phosphide (GaP) nanowire film electrodes have been prepared via solid sublimation of GaP powder using both gold (Au) and tin (Sn) nanoparticles as the vapor-liquid-solid (VLS) catalysts on Si(1 1 1) and GaP(1 1 1)B substrates. The resultant GaP nanowires are compared and contrasted in terms of structures and photoactivity in photoelectrochemical half cells. Raman spectra implicated a difference in the surface condition of the two types of nanowires. Complete wet etching removal of metallic VLS catalysts from the as-prepared GaP nanowires was possible with Sn catalysts but not with Au catalysts. The photoresponses of both Sn- and Au-seeded GaP nanowire films were collected and examined under 100 mW cm −2 white light illumination. Au-seeded nanowire films exhibited strong n-type characteristics when measured in nonaqueous electrolyte with ferrocene/ferricenium as the redox species while Sn-seeded nanowires showed behavior consistent with degenerate n-type doping. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides are of interest for energy applications, including energy generation in photoelectrochemical cells and as electrodes for next-generation electrochemical energy storage. Synthetic routes for such chalcogenides typically involve extended heating at elevated temperatures for multiple weeks. We demonstrate here the feasibility of rapidly preparing select sulfide compounds in a matter of minutes, rather than weeks, using microwave-assisted heating in domestic microwaves. We report the preparations of phase pure FeS 2 , CoS 2 , and solid solutions thereof from the elements with only 40 min of heating. Conventional furnace and rapid microwave preparations of CuTi 2 S 4 both result in a majority of the targeted phase, even with the significantly shorter heating time of 40 min for microwave methods relative to 12 days using a conventional furnace. The preparations we describe for these compounds can be extended to related structures and chemistries and thus enable rapid screening of the properties and performance of various compositions of interest for electronic, optical, and electrochemical applications. [ABSTRACT FROM AUTHOR]

The onset potential for H2 production from neutral water (pH 7) catalyzed by a platinum(ii) porphyrin (PtP-py) modified TiO2 electrode positions very close to the standard water reduction potential (less than 50 mV). H2 production is driven by the conduction band edge potential of TiO2 at the PtP-py-modified TiO2 cathode. [ABSTRACT FROM AUTHOR]

The onset potential for H2 production from neutral water (pH 7) catalyzed by a platinum(ii) porphyrin (PtP-py) modified TiO2 electrode positions very close to the standard water reduction potential (less than 50 mV). H2 production is driven by the conduction band edge potential of TiO2 at the PtP-py-modified TiO2 cathode. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) technology for the conversion of solar energy into chemicals requires cost-effective photoelectrodes to efficiently and stably drive anodic and/or cathodic half-reactions to complete the overall reactions for storing solar energy in chemical bonds. The shared properties among semiconducting photoelectrodes and photovoltaic (PV) materials are light absorption, charge separation, and charge transfer. Earth-abundant silicon materials have been widely applied in the PV industry, and have demonstrated their efficiency as alternative photoabsorbers for photoelectrodes. Many efforts have been made to fabricate silicon photoelectrodes with enhanced performance, and significant progress has been achieved in recent years. Herein, recent developments in crystalline and thin-film silicon-based photoelectrodes (including amorphous, microcrystalline, and nanocrystalline silicon) immersed in aqueous solution for PEC hydrogen production from water splitting are summarized, as well as applications in PEC CO2 reduction and PEC regeneration of discharged species in redox flow batteries. Silicon is an ideal material for the cost-effective production of solar chemicals through PEC methods. [ABSTRACT FROM AUTHOR]

Photoelectrochemical properties of ZnO nanorods (ZnO NRs) and poly(3-hexylthiophene) (P3HT) polymer hybrid photoanodes have been studied. The hybrid photoanodes demonstrated higher photoconversion efficiency, incident photon to current conversion efficiency (IPCE) and lower interfacial resistance compared to pristine ZnO nanorods and P3HT based electrodes. The origin of superior photoelectrochemical properties of ZnO/P3HT photoanodes has been explained using carrier transport mechanism at semiconductor/electrolyte junction. The stability of ZnO NRs/P3HT photoanode has been demonstrated. [ABSTRACT FROM AUTHOR]

Mesoporous metal oxide film electrodes consisting of derivatized 5.5 μm thick SnO2 films with an outer 4.3 nm shell of TiO2 added by atomic layer deposition (ALD) have been investigated to explore unbiased water splitting on p, n, and p+n type silicon substrates. Modified electrodes were derivatized by addition of the water oxidation catalyst, [Ru(bda)(4-O(CH2)3PO3H2)-pyr)2], 1, (pyr = pyridine; bda = 2,2'-bipyridine-6,6'-dicarboxylate), and chromophore, [Ru(4,4'-PO3H2-bpy) (bpy)2]2+, RuP2+, (bpy = 2,2'-bipyridine), which form 2:1 RuP2+/1 assemblies on the surface. At pH 5.7 in 0.1 M acetate buffer, these electrodes with a fluorine-doped tin oxide (FTO) back contact under ~1 sun illumination (100 mW/cm²; white light source) perform efficient water oxidation with a photocurrent of 1.5 mA/cm² with an 88% Faradaic efficiency (FE) for O2 production at an applied bias of 600 mV versus RHE (ACS Energy Lett., 2016, 1, 231-236). The SnO2/TiO2-chromophore-catalyst assembly was integrated with the Si electrodes by a thin layer of titanium followed by an amorphous TiO2 (Ti/a-TiO2) coating as an interconnect. In the integrated electrode, p+n-Si-Ti/a-TiO2-SnO2/TiO2|-2RuP2+/1, the p+n-Si junction provided about 350 mV in added potential to the half cell. In photolysis experiments at pH 5.7 in 0.1 M acetate buffer, bias-free photocurrents approaching 100 μA/cm² were obtained for water splitting, 2H2O → 2H2 + O2. The FE for water oxidation was 79% with a hydrogen efficiency of ~100% at the Pt cathode. [ABSTRACT FROM AUTHOR]

In this study, a non-enzymatic hydrogen peroxide photoelectrochemical (PEC) sensor based on nanoporous BiVO4 film electrode is fabricated by electrodeposit of nanoporous BiOI film on fluorine-doped tin oxide glass (FTO) and subsequent conversion to BiVO4 by annealing at elevated temperature. The electrode exhibits excellent visible light photoelectrochemical activity, and H2O2 works as a hole scavenger to react with light-induced electron holes on the valence band of BiVO4. Upon illumination and at applied bias potential of +0.2 V, the photocurrent density is linearly correlated to the concentration of H2O2. The linear determination range of H2O2 is 9.54-764.76 μM with a corresponding correlation coefficient of 0.9997, a detection limit of 1.59 μM (S/N=3), and sensitivity of 182.6 μA mM−1 cm−2. The optimum bias potential, most suitable film thickness, anti-interference performance, and impedance are also explored. The sensor shows good response towards H2O2 and displays a promising prospect for non-enzyme PEC H2O2 sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The substrate/photocatalyst interface determines the photoelectrode performance. • Ti/TiO x substrate forms type I heterojunction with the SnO 2 /SnS 2 photocatalyst. • In 2 S 3 transition layer blocks electron transfer from SnS 2 to the ITO substrate. • SnO 2 /SnS 2 form S-scheme heterojunction, beneficial for photoactivity and stability. • The growth mechanism of 3D-2D flower-like SnS 2 depends on the substrate material. In photoelectrochemical cells (PECs), the water-splitting process requires a directed electron flow. Therefore, the interface structure between the photoelectrode components is crucial for its photoelectrochemical activity. In the presented work, we performed studies to determine the effect of the heterojunctions formed between the applied photocatalysts (SnO 2 /SnS 2) and the substrate/photocatalyst. To this end, we prepared electrodes on three different substrates (ITO, Ti etched, and Ti covered with TiO x) composed of SnS 2 , SnO 2 , and SnO 2 /SnS 2 flower-like (3D-2D) structures. The layers were obtained via the chemical bath deposition method. The results revealed that depending on the applied substrate, the formed intermediate phases may block (In 2 S 3) or support (Ti n O 2n-1) the electron transfer via the substrate/photocatalyst interface. Among all samples, the SnO 2 /SnS 2 -based electrode obtained on Ti/TiO x substrate showed the best photoelectrochemical performance due to the formed type I (substrate/SnO 2) and S-scheme (SnO 2 /SnS 2) heterojunctions. This work demonstrates the effect of photoelectrode structure on its electrochemical activity. Based on the analysis of the (micro)structural, surface, optical, and photoelectrochemical properties, we have proposed: (1) the substrate/photocatalyst interface structures, (2) a band diagram with charge transfer mechanism, and (3) the growth mechanism of the nanostructured layers, explaining the formation of surface defects. [ABSTRACT FROM AUTHOR]

Compared to rigid CdS/glass electrodes, flexible pristine CdS electrodes have not been described in photoelectrochemical (PEC) based light-to-electricity conversions, despite wide descriptions of their preparations and characterizations. CdS film electrodes, deposited on flexible tin-doped indium oxide/polyethyleneterephthalate (ITO/PET) substrates, have been prepared here by both chemical bath deposition (CBD) and electrochemical deposition (ECD). The film PEC characteristics have been investigated here. With a very low thickness, the flexible ECD-CdS electrode fails to show measurable PEC performance. On the other hand, with higher film thickness, the CBD flexible electrode shows soundly high PEC performance. To further improve PEC characteristics of the flexible CBD-CdS/ITO/PET electrodes, various parameters have been varied, such as number of deposition cycles, annealing temperature, cooling rate and type of redox couple. Among the studied films, the four-layered CBD-CdS/ITO/PET film, annealed at 125 °C and quickly cooled, exhibits highest PEC performance and stability, with conversion efficiency higher than 1.2% in polysulfide redox couple. The results show that the flexible CBD-CdS/ITO/PET electrode may compete with earlier rigid CdS film electrodes deposited on fluorine doped tin oxide/glass substrate. Annealing and quick cooling, of flexible pristine CdS/ITO/PET electrode, speed up charge transfer and consequently improve PEC performance. [Display omitted] • Flexible pristine CdS films are deposited onto ITO/PET substrates by CBD and ECD methods. • Films are optimized by deposition time & layer, annealing temperature and cooling rate. • Flexible CBD-CdS/ITO/PET electrode competes with rigid CdS systems in PEC performance. • High PEC efficiency and stability are achieved by film 125 °C annealing and quick cooling. [ABSTRACT FROM AUTHOR]

The alarming energy and environmental crisis of our modern era necessitates scientists to propose alternatives to replace the scarce and harmful fossil fuels. The Sun, as a free, and abundant clean energy resource, presents a motivation for researchers to convert the sunlight to electrical power and store the H 2 as an energy carrier by developing solar cells as well as water splitting devices, respectively. One of the fundamental parts of a solar energy convertor (solar cell/photoelectrochemical device), where the reduction reaction occurs, is the counter electrode (CE); the CE is commonly based on rare Pt. It is critical to substitute costly CEs with efficient, low-cost replacements, which would draw widespread attention to two-dimensional (2D) materials. Over the past few years, graphene and graphene-like materials, especially transition metal dichalcogenides (TMDC), and also their hybrid systems have been suggested to be new path to electronic/optoelectronic devices for their unusual properties. The growing number of studies and research articles published on 2D counter electrodes call for a comprehensive outlook on new approaches to electrode fabrications and optimization methods, along with a clear classification of 2D material-based counter electrodes. Essentially, reviewing the most accredited papers, much light is shed on a global energy research roadmap accelerating scientists’ efforts in this area. In this review, we have focused on 2D materials used as CEs; mainly graphene sheets in pure, doped, or composite forms; as well as TMDC-based CEs. In each section, the most common syntheses and characterization approaches are reviewed as well as introducing the most efficient systems. [ABSTRACT FROM AUTHOR]

Alleviating charge recombination at the electrode/electrolyte interface by introducing an overlayer is considered an efficient approach to improve photoelectrochemical (PEC) water oxidation. A WO3 overlayer with dual oxygen and tungsten vacancies was prepared by using a solution-based reducing agent, LEDA (lithium dissolved in ethylenediamine), which improved the PEC performance of the mesoporous WO3 photoanode dramatically. In comparison to the pristine samples, the interconnected WO3 nanoparticles surrounded by a 2-2.5 nm thick overlayer exhibited a photocurrent density approximately 2.4 times higher and a marked cathodic shift of the onset potential, which is mainly attributed to the facilitative effect on interface charge transfer and the improved conductivity by enhanced charge carrier density. This simple and effective strategy may provide a new path to improve the PEC performance of other photoanodes. [ABSTRACT FROM AUTHOR]

We fabricate photoelectrochemical cells ( PECs) using In2S3/ In2O3 double-layer composite as a working electrode in the presence of single-walled carbon nanotubes ( SWCNTs). Simple solution methods, such as spray-coating and chemical bath deposition, were used to assemble each layer in the PECs. We apply pristine SWCNTs, semiconducting SWCNTs (s- SWCNTs), and metallic SWCNTs (m- SWCNTs) to the PECs, and measure their solar performances, incident photon to charge carrier efficiency, and electro-impedance spectra. Field emission is also measured to explain the enhanced electric field of each cell. [ABSTRACT FROM AUTHOR]