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Developing efficient hole transport layers and water oxidation electrocatalysts is vital for improving the performance of photoelectrochemical (PEC) devices for water-splitting. In this work, we synthesized Co 3 O 4 nanoparticles/Ti 3 C 2 -MXene hybrid material and utilized it as a dual-function material to transport the photogenerated holes and catalyze the water oxidation reaction. It was found that the modification of BiVO 4 with Co 3 O 4 /Ti 3 C 2 -MXene prolonged the lifetime of the photogenerated holes by 13.7-fold (i.e. from 0.26 s for BiVO 4 to 3.56 s for Co 3 O 4 /Ti 3 C 2 /BiVO 4) and significantly reduced the charge transfer resistance. The modification of BiVO 4 with only Ti 3 C 2 -MXene resulted in significant surface recombination more likely due to the high concentration of the accumulated holes in the Mxene layer because of its low electrocatalytic activity toward water oxidation reaction. Employing the Co 3 O 4 /Ti 3 C 2 -MXene hybrid material significantly reduced the rate constant of surface recombination and dramatically enhanced the charge transfer efficiency (i.e. from 0.17% for BiVO 4 to 14.0% for Co 3 O 4 /Ti 3 C 2 /BiVO 4 at 0.65 V RHE). Under optimized conditions, the Co 3 O 4 /Ti 3 C 2 /BiVO 4 photoanode was able to deliver 5.05 mA cm−2 at 1.23 V RHE and outperforms Ti 3 C 2 /BiVO 4 and Co 3 O 4 /BiVO 4 photoanodes. Moreover, it showed high stability for over 50 hours and reached a Faradaic efficiency of 90%. An applied bias photo-to-current efficiency (ABPE) value of 1.71% at 0.62 V Pt was obtained for the overall water splitting. This work provides a facile method to reduce surface recombination and enhance the stability and PEC efficiency of BiVO 4 photoanodes via the modification with dual-function oxygen evolution catalyst/hole transport layer hybrid material. [Display omitted] [ABSTRACT FROM AUTHOR]

• Investigating excited hole transfer from n-type Si photoelectrode to Pt cocatalyst. • In situ ATR-SEIRAS for excited carrier transfer employing adsorbed CO as a probe. • Observation of excited hole migration from Si photoelectrode to Pt oxygen evolution cocatalysts. • Local potential shift of Pt cocatalyst contributes the photoelectrochemical water oxidation. The development of efficient photoelectrode material for water-splitting reactions has received considerable attention as it produces hydrogen gas from water using solar energy. Photoexcited holes migrate to the surface of an n-type photoelectrode oxidizing water to oxygen, and excited electrons migrate to the counter electrode reducing protons to hydrogen. However, there is limited knowledge of excited carrier transfer. Therefore, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) has been used to investigate the excited hole migration from n-type Si photoelectrode to Pt oxygen evolution cocatalysts by monitoring the frequency of CO adsorbed on the Pt cocatalysts. At the positive potential of Si photoelectrode under UV irradiation, the SEIRA spectrum of the CO adsorbed on the Pt cocatalyst shifted to higher wavenumbers owing to the excited hole transfer from n-type Si photoelectrode to the Pt cocatalyst attributed to band bending at the interface between the Si photoelectrode and Pt cocatalysts. It was successfully demonstrated that the regulation of photoexcited carriers was crucial for enhancing the photoelectrochemical activity of water splitting. [ABSTRACT FROM AUTHOR]

This work investigates the n-Si photoanodes corrosion protection by Atomic Layer Deposition (ALD) of a TiO2 film. A specific electrochemical experimental sequence (including successive rest potential measurements and voltammetries under illumination or not) has been established to study the stability of the electrodes in KOH. Depending on the deposition conditions (precursor composition and temperature), the electrochemical properties of the layers are different. The photoanodes coated using titanium tetraisopropoxide (TTIP) at low temperature exhibit a low photocurrent (jph) that is progressively enhanced during the electrochemical sequence and their stability decreases. When using tetrakis(dimethylamido)titanium (TDMAT), the jph is almost constant and the film prevents from corrosion. The characterizations show that the ALD parameters drive the microstructure of the layer that is found critical for the electrochemical response. A hydrogen doping occurring during the open circuit potential measurements under illumination is evidenced by IR spectroscopy. It is mainly localized at the grain boundaries and pores of the layers as well as in the n-Si and it modifies the charge transfer at the electrode/solution junction and the hydrogen diffusion weakens the film causing the Si corrosion. The different charge transfer mechanisms are finally proposed depending on the ALD conditions and the film thickness. [ABSTRACT FROM AUTHOR]

• Functional MoO 3 photoanode with self-photorechargeability was synthesized via AACVD. • Synergistic role of Pt cocatalyst was examined through experiments and DFT study. • Current and charge densities for Pt/MoO 3 photoanode were improved significantly. • DFT simulated and explained the slow decay in charge density observed in Pt/MoO 3. Here, we synthesize a functional MoO 3 photoanode with self-photorechargeability through aerosol-assisted chemical vapour deposition. The role of platinum co-catalyst in Pt-mediated MoO 3 photoanode (Pt/MoO 3) was investigated to improve and maintain its charge density to enable photoelectrochemical water oxidation under non-irradiated condition. Raman spectroscopy and X-ray diffraction analyses showed that the orthorhombic phase of MoO 3 was formed with significant Raman diffraction peaks and crystal planes were grown in the (0 k 0) crystallographic orientation for better charge storage capacity in MoO 3 photoanodes, respectively. Furthermore, the chronoamperometry measurements of the Pt/MoO 3 photoanode revealed that both current and charge densities were improved by 29 times and 94 times, respectively, than the bare MoO 3 photoanode. This is attributed to the presence of Pt co-catalyst, which acts as an effective electron sink in inhibiting the recombination of photogenerated charge carriers. A density functional theory simulation was then used to validate the experimental findings and fundamental mechanisms of self-photorechargeability in Pt/MoO 3 photoanodes. It was found that the distinct characteristic of slow decay in charge density of Pt/MoO 3 photoanode is due to the formation of alkali cation/metal layer, where the intercalated photogenerated electrons require a higher energy to overcome the energetic barrier of the alkali cation/metal layer. [Display omitted] [ABSTRACT FROM AUTHOR]

The current work investigates the morphology, crystallinity and photoelectrochemical (PEC) performance of bismuth sulfide/silver sulfide/zinc oxide nanorods (Bi 2 S 3 /Ag 2 S/ZnO NRAs) photoelectrodes as prepared at different annealing temperature. ZnO NRAs was initially grown hydrothermally, deposited in sequence with Ag 2 S and Bi 2 S 3 via successive ionic layer adsorption and reaction (SILAR) method before undergoing the annealing treatment. The optimised photoelectrode (Bi 2 S 3 /Ag 2 S/ZnO NRAs-400 °C) possesses an optical bandgap of 1.60 eV extending the absorption edge of ZnO to visible light spectrum. The current-voltage characterization of Bi 2 S 3 /Ag 2 S/ZnO NRAs photoelectrodes revealed that the photocurrent density and photoconversion efficiency were strongly dependent on the annealing temperature. The PEC study shows that the photoelectrode annealed at 400 °C achieved impressive photocurrent density of 12.95 mA/cm2 at +0.5 V (vs Ag/AgCl/saturated KCl) under 100 mW/cm2 illumination with superior photoconversion efficiency of 12.63%. This improvement is due to the cascade-designed band structure alignment of Bi 2 S 3 /Ag 2 S/ZnO/ITO and to the brilliant role of Ag 2 S as an intermediate layer that reduced random chance of electron-hole (e− - h+) pairs recombination and improved the electrons collection efficiency. This work is highly anticipated to give contribution on further utilisation of Bi 2 S 3 /Ag 2 S/ZnO NRAs as a promising semiconductor material in PEC related applications. [ABSTRACT FROM AUTHOR]

1 A facile method for preparing Cu(I) vanadate-BiVO 4 p-n heterojuction photoanode. 2 Role of Cu(I) vanadate in improving the kinetics of charge transport was uncovered. 3 Efficient interfacial charge transfer and high photostability was achieved. Bismuth vanadate (BiVO 4) has been identified as one of the promising photoanode materials for photoelectrochemical (PEC) water splitting. Nevertheless, the serious charge recombination and sluggish kinetics of oxygen evolution reaction (OER) are the main factors limiting its PEC performance. In this contribution, copper incorporated nanostructured BiVO 4 photoanodes (nanoCu:BiVO 4) were prepared by converting the electrodeposited BiOI nanosheets in the presence of copper and vanadium sources and subsequent thermal treatment. nanoCu:BiVO 4 prepared with a suitable amount of copper consists of well-interconnected BiVO 4 nanoparticles coated with p-type Cu(I) vanadate. The well-interconnected structure improved the kinetics of the charge transport, whereas n–p heterojunction formed between BiVO 4 and Cu(I) vanadate remarkably improved the efficiencies of charge separation and interfacial charge transfer. Further improvement in OER kinetics and photostability of nanoCu:BiVO 4 was demonstrated by interfacing nanoCu:BiVO 4 with nickel-iron oxyhydroxide based OER catalyst. [ABSTRACT FROM AUTHOR]

Ni/Si-doped TiO2 nanostructures were prepared by anodizing Ti-1Ni-5Si alloy. The electrochemical reduction in the aqueous solutions was a simple and effective method to self-dope Ti3+ into Ni/Si-doped TiO2 nanostructures. It was found that electrochemical reduction in neutral aqueous solution (pH 7) was more effective than that in either acidic aqueous solution (pH 3) and basic aqueous solution (pH 13). The stable reduced Ni/Si-doped TiO2 photoanode obtained in the neutral aqueous solution exhibited an excellent photoelectrochemical water splitting performance due to the increased Ti3+ and oxygen vacancies species, which not only extended the visible-light absorption range but also promoted the charge transfer and separation process. A remarkable photocurrent density of 2.41 mA cm−2 at 0 V vs Ag/AgCl was achieved, corresponding to a photoconversion efficiency of 1.12%, which was 5.9 times that of the undoped TiO2 photoanode (0.19%). [ABSTRACT FROM AUTHOR]

Using electrochemical anodization of tungsten foil in afluorinated-based electrolyte, the twisted WO3 nanorods (T-WO3NRs)were grown, and the film properties were controlled by post-annealing conditions. The anodized WO3 material was composed oftwo distinct layers; the T-WO3NRs which functions as an active layer for the PEC reaction and another compact WO3 (C-WO3) barrier which acts as a blocking layer for the charge transport. From more resistance of thicker C-WO3 layer, to minimize theformation of the C-WO3 layer under constant applied voltage, we performed rapid-thermal annealing under air ambient as a post-thermal treatment. As the post-annealing time increased, the thickness of T-WO3 NRs layer remained at approximately 680 nm, but the C-WO3 thickness gradually increased from about 91 nm at 1 min to 633 nm at 120 min. Unexpectedly, the anodic WO3 filmhaving a compact layer thickness of about 475 nm exhibited the highest PEC performance, corresponding to a photocurrent density of 0.75 mA cm−2 at 1.23 V vs reversible hydrogen electrode, subsequently followed by anodic WO3 films with less thick compact layers. This suggests that the C-WO3 layer promotes the charge separation/transfer events by formation of cascading band alignments between the T-WO3 NR and C-WO3layers. [ABSTRACT FROM AUTHOR]

The influence of surface treatment of as-synthesized Cu2ZnSnS4 (CZTS) thin films on the photocurrent response in the photoelectrochemical cell with Eu3+ contact has been studied. With our work we are the first, to our knowledge, to show that in order to achieve the maximal photocurrent response of CZTS, dissolution of copper sulfide in a KCN solution and subsequent dissolution of ZnS in a HCl solution is insufficient. An additional treatment in a KCN solution for only 10 s can results in the highest photocurrent density. XPS, photoelectrochemical and the Mott-Schottky measurements reveal a negatively charged layer of surficial chlorides on the CZTS film. This layer was captured during removal of the ZnS secondary phase from CZTS film surface in a HCl solution. It has been shown that this layer is the reason why it was impossible to reach the maximum photocurrent. XRD, SEM and XPS measurements demonstrated the dissolution of copper sulfide in a KCN solution, zinc sulfide in a HCl solution and removal of a thin layer of copper chloride during a short (10 s) additional treatment in a KCN solution. [ABSTRACT FROM AUTHOR]

We developed the multilayered fluorine doped SnO2 (abbreviated as FTO) inverse opal (IO)/WO3/BiVO4 film by sol-gel based spin coating, subsequently followed by facile electrodeposition. Above FTO IO template, both WO3 and BiVO4 layers were prepared by the electrodeposition methods in the variation of charge amount of 200–1,000 mC cm−2 and of 300–1,500 mC cm−2, respectively. On increasing the loaded charge amount of WO3 under the constant loaded amount of BiVO4, the light absorption in the near 400 nm is increased to steadily enhance PEC performance. In contrast, the further loaded WO3 layer of 800–1,000 mC cm−2 on FTO IO film degrades PEC activity, due to the increase of the intrinsic material and interfacial resistances. Meanwhile, on increasing the electrodeposited charge amount of BiVO4 under the constant charge amount of WO3, the light absorption toward the visible wavelength is sharply increased, and gives rise to the enhancement of PEC performance; and conversely, the more loaded BiVO4 of 1,200–1,500 mC cm−2 induced the decay of PEC performance. The optimum condition in FTO IO/WO3 (600 mC cm−2)/BiVO4 (600 mC cm−2) film was well established, and the function or role of each layer was confirmed using photoluminescence, charge separation/transfer efficiency, and photovoltage-time spectra. [ABSTRACT FROM AUTHOR]

• The conversion of carbon dioxide (CO 2) into fuels using solar energy. • Various materials improved the solar to energy conversion efficiencies for photocatalysts. • III-V semiconductors, oxide semiconductors and perovskites materials were highlighted. The conversion of carbon dioxide (CO 2) into fuels using solar energy have been studied extensively since it is very attractive in that this can provide a solution to both problems of the increasing carbon dioxide concentration in the atmosphere and the finding new energy sources. Various materials have been explored to improve the solar to energy conversion efficiencies for photocatalysts or photoelectrodes in light-assisted photoelectrochemical (PEC) systems. Although lots of progress have been, the efficiencies still need to be increased for future commercial applications. This review is focused on the recent works related to III-V semiconductors, oxide semiconductors and perovskites materials and the achievement by modifying the physical and chemical properties of these materials. Photovoltaic cell biased PEC system in which the absorption subsystem and the reduction subsystem can be optimized independently is described and a prospect in the CO 2 photoconversion systems is discussed. [ABSTRACT FROM AUTHOR]

N-type BiVO4 films coupled with p-type copper oxide nanoparticles were investigated as photoanodes for water oxidation. Compared with the BiVO4 film, the Cu2O/BiVO4, CuO/BiVO4 and CuxO/BiVO4 films all showed significantly improved photoelectrochemical water oxidation activity and stability. As expected, the radiative recombination of charge on the three kinds of copper oxide/BiVO4 films was decreased due to the p-n junction effect between copper oxide and BiVO4. However, our investigations indicated that the electrocatalytic water oxidation on the copper oxide could be initiated when the copper oxide/BiVO4 photoanodes were irradiated by solar light; therefore, the copper oxide-coupling resulted in a more obvious improvement in the water oxidation kinetics of BiVO4 than the thermodynamic improvement in the charge separation of BiVO4. Of the three kinds of copper oxide/BiVO4 films, the CuxO/BiVO4 film comprising BiVO4 film coupled with a combination of Cu2O/CuO nanoparticles showed the best solar water oxidation performance due to the better electrocatalytic activity for water oxidation of CuxO compared with Cu2O or CuO alone. The kinetic investigations and analyses in the present work provide comprehensive insight into the mechanism of the copper oxide/BiVO4 photoanodes for solar water oxidation. [ABSTRACT FROM AUTHOR]

• The amorphous TiO 2 granular nanodisks were prepared on porous Ti foam. • The TF-30 photoelectrode prepared with 30 V exhibited the outstanding photoelectric properties. • The PEC mechanism and active species for dye degradation were studied. Amorphous TiO 2 granular nanodisks were synthesized by the simple anodization of porous Ti foam, and the morphology and photoelectrochemical performance were significantly influenced by anodization voltages. The investigation results showed that TiO 2 nanotubes, nanodisks and nanospheres were fabricated at the anodization voltages between 15 V and 45 V, respectively, and TiO 2 granular nanodisks showed the excellent photoelectric conversion and photoelectrocatalytic (PEC) properties. Under solar irradiation, the photocurrent density and photovoltage achieved 417.45 µA/cm2 and −0.23 V/cm2, and the PEC removal of MO, MB dyes and Cr (VI) achieved 61.05%, 93.77% and 51.82%. The excellent photoelectrochemical performance could be ascribed to the high surface area of Ti foam and multiple active adsorption sites of TiO 2 granular nanodisks. The novel 3D photoelectrode would provide new insight in environmental remediation and solar energy conversion. [ABSTRACT FROM AUTHOR]

Cu2O based photoelectrodes have demonstrated an impressive photoelectrochemical (PEC) performance in solar hydrogen evolution. However, Cu2Ois prone to photo-corrosion in the electrolyte, and the limited electron diffusion length restrains the efficient collection of photogenerated charges. In this work, Cu2O nanowire (NW) arrays have been grown on Cu foam substrates. The performance and stability of Cu2O NW photoelectrode were further improved by adopting an additional Cu2O layer and a surface protection layer of carbon. This configuration, Carbon/Cu2O/Cu2O NW/Cu foam, showed a continuous photocurrent of ~ 4.2 mA•cm-2 in 3600 s in neutral Na2SO4 solution. [ABSTRACT FROM AUTHOR]

In this work, cobalt-phosphate (Co-Pi) cocatalyst is deposited on the surface of BiFeO3 (BFO) thin film photoanode for enhanced photoelectrochemical (PEC) performances. The prepared Co-Pi/BFO thin film is composed of irregular rhombohedral BFO nanoparticles which are uniformly coveredwith a layer of amorphous Co-Pi, and the corresponding PEC performance is remarkably improved with a negatively-shifted onset potential from -0.058 V (BFO) to -0.130 V (Co-Pi/BFO). The photocurrent density of Co-Pi/BFO thin film photoanode measured at 0 V (vs. Ag/AgCl) under visible light irradiation is as high as ~0.050 mA cm-2 (nearly 8 times that of the prepared BFO thin film photoanode), which rivals or exceeds those of state-of-the-art BFO-based thin film photoelectrodes. On the basis of PEC measurement results, the enhanced PEC performance of Co-Pi/BFO photoanode can be attributed to the higher carrier concentration, the more efficient separation and transfer process of photogenerated charges and the lower electron/hole recombination probability induced by Co-Pi cocatalyst. In addition, the possible PEC mechanism of the Co-Pi/BFO photoanode is also discussed. The present work validates the feasibility of Co-Pi cocatalysts coupled with other photoanode systems for pursuing highly efficient PEC performances of water oxidation. [ABSTRACT FROM AUTHOR]

• In 2 O 3 /CeO 2 /HATP hybrid photocatalysts were successfully prepared. • Cerium oxide defect state effectively promotes the charge separation. • The as-prepared photocatalysts exhibit excellent yields for CO and CH 4 production. A series of novel porous indium (III) oxide (In 2 O 3) and nanocubic cerium oxide (CeO 2) loading HCl treated attapulgite (HATP) ternary photocatalysts were successfully synthesized. Simultaneously, all photocatalysts were performed the CO 2 reduction under UV-light. To explore the crystal structures, morphologies and electrochemical characteristics of as-synthesized samples, the XRD, SEM and TEM, and transient photocurrent techniques were performed in this work. Besides, as an optimized In 2 O 3 /CeO 2 /HATP sample presents the highest activity for CO (32.03 µmol/g) and CH 4 (16.94 µmol/g) yields, which is 6.11-fold and 6.78-fold times higher than those of pure CeO 2 under UV-light (8 W) irradiation. Schematic illustration of 10In/Ce/HATP-20 heterostructure for CO 2 photoreduction under UV-light irradiation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Low intensity indoor lightings are often wasted and unutilized, when they could be harvested to produce electrical energy. Unfortunately there is currently no solar cells which could harvest low light intensity efficiently. Therefore, this work reports the synthesis of energy transfer redox couples (ETRCs) that aid in the harvesting of low light intensity for photoelectrochemical cells. Such ETRCs are excellent choices as electrolytes in solid-state photoelectrochemical cells owing to their multifunctional attributes like faster dye regeneration, more efficient light absorption and faster energy transfer kinetics. Electrochemical characterizations reveal that Forster Resonance Energy Transfer (FRET) is occurring between ERTC electrolyte (donor) and the N719 dye (acceptor). Photovoltaic efficiency of the reported device is 28% higher than the conventional silicon solar cells, tested under low light intensity. Additionally, the idiosyncratic design of this device makes it versatile to be used in indoor conditions or can be mounted at a wide range of incidence angle with an ability to retain a high efficiency of 21.08%. Superior ionic-conductivity imparted by the single-component electrolyte provides a platform for future directions in energy harvesting and storage. Image 1 • New organic-ionic redox couple based DSSCs with a unique property to harness low intensity indoor lights. • Single component organic ionic conductor owns dual nature; one as a redox mediator and other as a light harvester. • ETRC-1 based DSSC exhibited highest efficiency of 21.0% under low-light intensity owing to FRET mechanism. • FRET mechanism reported for the first time between electrolyte/photosensitizer without any secondary additive. [ABSTRACT FROM AUTHOR]

Ni3S2/CdS nanocomposites based on zero-dimensional Ni3S2 nanoparticles (NPs) and one-dimensional CdS nanowires (NWs) were synthesized via a two-step solvothermal approach. These nanocomposites were characterized using a combination of experimental techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, and photoelectrochemistry method. The Ni3S2/CdS nanocomposites exhibit much higher photocatalytic hydrogen evolution activity than individual CdS NWs or Ni3S2 NPs under visible light irradiation (λ ≥ 400 nm) from water. Photoelectrochemical (PEC) and photocatalytic properties of the Ni3S2/CdS nanocomposites were investigated as a function of the molar ratio between Ni3S2 and CdS. In addition, ultrafast transient absorption (TA) spectroscopy was employed to probe the charge carrier dynamics, which is about four times shorter in 10%-Ni3S2/CdS than pure CdS NWs. These results suggest efficient charge transfer between CdS and Ni3S2 at the interface, which is desired for PEC and photocatalytic applications [ABSTRACT FROM AUTHOR]

The theory of intensity-modulated photocurrent spectroscopy (IMPS) is extended to consider the two-electron two-proton hydrogen evolution reaction at p-type semiconductor photocathodes. A generalized reaction scheme is described, and two limiting cases are analyzed. The first involves photoelectrochemical desorption of hydrogen by electron/proton transfer and the second chemical desorption by reaction of adsorbed hydrogen atoms. Expressions are derived for the IMPS responses in the two cases as well as for the modulated surface electron concentration, which is related to the quasi Fermi level at the interface. The surface electron concentration expressions can be used to interpret electrical, optical, or microwave experiments that detect the excess electron concentration. The IMPS responses calculated for the two limiting cases are fitted to a simplified IMPS model that gives rate constants kt nd kr for charge transfer and recombination respectively.kt and kr are then related to the rate constants describing the two limiting schemes for the light-driven hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting has the potential to significantly reduce the costs associated with electrochemical hydrogen production through the direct utilization of solar energy. Many PEC cells utilize liquid electrolytes that are detrimental to the durability of the photovoltaic (PV) or photoactive materials at the heart of the device. The membrane-electrode-assembly (MEA) style, PEC cell presented herein is a deviation from that paradigm as a solid electrolyte is used, which allows the use of a water vapor feed. The result of this is a correspondent reduction in the amount of liquid and electrolyte contact with the PV, thereby opening the possibility of longer PEC device lifetimes. In this study, we demonstrate the operation of a liquid and vapor-fed PEC device utilizing a commercial III-V photovoltaic that achieves a solar-to-hydrogen (STH) efficiency of 7.5% (12% as a PV-electrolyzer). While device longevity using liquid water was limited to less than 24 hours, replacement of reactant with water vapor permitted 100 hours of continuous operation under steady-state conditions and diurnal cycling. Key findings include the observations that the exposure of bulk water or water vapor to the PV must be minimized, and that operating in mass-transport limited regime gave preferable performance. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) characteristics of GaN grown by hydride vapor-phase epitaxy (HVPE) with different polarizations were studied and compared. The polar GaN used a (0001)-oriented plane and the semipolar GaN used a (20-21)-oriented plane. The photocurrent density of polar GaN exhibited a two-fold increase over that of semipolar GaN. Bulk GaN sustained water splitting up to 400 h at 0 V versus the reference electrode. To the best of our knowledge, this is the highest value reported for PEC water-splitting stability. This demonstrates the potential of GaN thin films grown by HVPE for application in large-scale solar-fuel conversion. [ABSTRACT FROM AUTHOR]

CdS quantum dot and ZnS quantum dot as passivation layers were deposited on the surface of TiO2/C-TiO2/TiO2 multilevel structure photoanode. And solar cells were assembled by using the photoanode. The photoanodes were characterized by X-ray diffraction, transmission electron microscope, fourier transform infrared and ultraviolet-visible adsorption spectra. Photoelectrochemical properties of devices were tested by electrochemical workstation. The results show that the optimum conditions for the photoelectric performance of the device are cadmium acetate as the cadmium source and sensitization 9 times, and the TiO2 film layer is 3 layers. Under such process conditions, the short-circuit current density (Jsc) is 2.28 mA/cm2, open-circuit voltage (Voc) is 0.30 V, fill factor (FF) is 0.45, and photoelectric conversion efficiency (η) is 0.14%. After introducing carbon quantum dots, the filling factor is increased by 100% to 0.40, and the all-optical conversion efficiency is improved by 28%, to 0.18%. [ABSTRACT FROM AUTHOR]

Achieving highly effective water splitting based on conventional TiO 2 photoanode is challenging due to its poor visible light response and low electrical conductivity. Herein, a Bi 2 MoO 6 /TiO 2 heterojunction with a suitable band structure is constructed to broaden light absorption and accelerate oxidation kinetics. In particular, the highest photocurrent density (0.35 mA cm−2 at 1.23 V vs. RHE) of Bi 2 MoO 6 /TiO 2 is 2.1 times higher than that of pristine TiO 2. The integrated Bi 2 MoO 6 nanoflakes enrich more reactive sites and charge transfer tunnels. The surface hole injection efficiency and electron lifetime of Bi 2 MoO 6 /TiO 2 are 1.4 and 5.5 times larger than those of bare TiO 2 , respectively. Additionally, the activation energy and charge transfer resistance of Bi 2 MoO 6 /TiO 2 electrodes are decreased remarkably, dramatically promoting the separation of electron-hole pairs. This work offers a novel strategy for TiO 2 -based heterojunction with great potential for application in photoelectrochemical water splitting. [Display omitted] • Bi 2 MoO 6 /TiO 2 heterojunction prolongs electron lifetime and enlarges surface hole injection efficiency. • Bi 2 MoO 6 nanoflakes broaden light absorption, enrich reactive sites, and provide charge transfer tunnels. • The charge transfer resistance of Bi 2 MoO 6 /TiO 2 photoanode is decreased remarkably. • Twice enhancement on photocurrent density achieved by Bi 2 MoO 6 /TiO 2 heterojunction. [ABSTRACT FROM AUTHOR]

Potential synthesis of ternary chalcogenide nanocomposite to showcase a practical electronic pathway to improve photocatalytic efficiency was carried out. In the present study, AgBiS 2 nanorod-shaped with remarkably visible-light absorption was prepared using solvothermal techniques. This material was employed in photocatalytic degradation of amoxicillin (AMX) under visible light irradiation. The results indicated more than 90% degradation of AMX under 60 min having a corresponding bandgap of ∼2.19 eV. In the verge of understanding the photogenerated separation of electron-hole pair, VB and CB potentials were calculated to be 2.06 eV and − 0.76 eV, proposing a possible pathway for the degradation study. The photogenerated intermediates were identified using LC-MS analysis and the mineralization was followed using TOC analysis. A scavenging experiment showed a potential reactive oxygen species involved in the oxidation of organics that proved effective in three consecutive trials.In addition, antibacterial and antibiofilm activity showcased fair efficiency of the material, especially the presence of Ag+ in AgBiS 2 improves antimicrobial activity. In case of antibiofim activity, 4 × 107 CFU/mL were seen to be most effective for the biomass formation of the biofilms. [Display omitted] • A photocatalytic degradation system was assembled using AgBiS 2 catalyst. • AgBiS 2 via photocatalysis is efficient in the degradation of amoxicillin. • The catalyst proves to be an efficient antibacterial agent for the destruction of bacterial cell walls and cell lysis. • AgBiS 2 proves to be bi-functional, stable, efficient, non-toxic, and efficient in water/wastewater treatment. [ABSTRACT FROM AUTHOR]

Fe 2 O 3 , as a substance that exists in nature in large quantities, has been widely paid close attention by many scholars because of its excellent properties. Fe 2 O 3 can be divided into four phases depending on the crystal structure. As a narrow band gap semiconductor, β-Fe 2 O 3 has a band gap of about 1.77–1.83 eV, which is much lower than the average band gap of Fe 2 O 3 (2.1 eV), and its theoretical saturated photocurrent density is 35% higher than that of α-Fe 2 O 3 , showing excellent light absorption characteristics and water oxidation capacity, which is a promising photoanode material. As the only polycrystalline phase of iron oxide that exhibits paramagnetism at room temperature, it also has a very bright prospect in the field of magnetic resonance. This paper focuses on the review of rare phase β-Fe 2 O 3. Firstly, the crystal structure, magnetism of β-Fe 2 O 3 and the mature methods for preparing pure β-Fe 2 O 3 are summarized. Secondly, the conversion relationships between β phase and other phases of Fe 2 O 3 is reviewed, and the important factors affecting this process are summarized. As for the improvement and applications, it points out a variety of improvement methods such as heterojunction, element doping and morphology control, and discusses the applications of β-Fe 2 O 3 in many fields such as photocatalysis, Fenton oxidation, photochemical hydrogen production, biomedicine and toxic gas detection. Finally, the application prospect and challenges of β-Fe 2 O 3 are prospected. This paper aims to further demonstrate the latent capacity of β-Fe 2 O 3. It also provides ideas for the application of this substance in other environmental remediation fields. [Display omitted] ● The crystal structure and magnetism of rare phase β-Fe 2 O 3 are discussed in detail. ● Principle of β-Fe 2 O 3 conversion to other phases and the key factors are proposed. ● The methods of β-Fe 2 O 3 performance improvement are proposed. ● The applications of β-Fe 2 O 3 in different fields of environmental governance. [ABSTRACT FROM AUTHOR]

A simple "on-off-on" photoelectrochemical (PEC) thrombin (TB) aptasensor has been constructed with the assistant of the elaborately designed matrix prepared by 3,4,9,10-perylene tetracarboxylic acid (PTCA), gold nanoparticles (Au NPs) and cadmium sulfide quantum dots (CdS QDs). PTCA, Au NPs and CdS QDs are used as the photoactive material, photosensitizer, and postpositive photoelectric material respectively. The preparation process of the matrix was characterized via photoelectrochemical and electrochemical technologies. The dynamic concentration monitor of TB via PEC. The results show that the sensitive TB detection can be observed on the proposed "on-off-on" aptasensor with a linear range from 1.0 × 10-6 to 1.0 × 10-14 mol · L-1 and the detection limit of 3.3 fmol · L-1. Through the synergistic effect of the matrix, the obtained signal intensity is 1.6-fold higher than the initial one. The aptasensor also possesses high selectivity to the target TB over other interfering proteins or amino acid, it can be employed to detect TB in human serum samples. This approach reveals a promising avenue for increasing photocurrent efficiently by bringing in postpositive photoelectric material. [ABSTRACT FROM AUTHOR]

The recent surge of alternative clean energy with minimal environmental impact in a cost-effective way has attracted great interest in the exploration of new materials and/or structures as efficient electrodes for industry-level (photo)electrochemical water splitting. Delafossites with a general formula of ABO2 as a type of earth-abundant materials are expected to serve as ideal alternatives for water electrolysis. In this work, by fine-tuning the synthesis procedure of delafossite CuGaO2 via surfactant assisted hydrothermal route, we investigated the dependence of their (photo)electrochemical properties on geometry factors. More specifically, the synthesized CuGaO2 samples were characterized by powder XRD, SEM, EDX, XPS, FT-IR, UV-Vis, and BET surface area measurements. Moreover, their electrocatalytic and photoelectrocatalytic performance were tested and compared toward oxygen evolution reaction (OER). Based on cyclic voltammetry and electrochemical impedance spectroscopy, their onset potential, current density, Tafel slope, charge transfer resistance, and stability were investigated. It was found that the synthesized delafossite CuGaO2 nanoflakes with the smallest dimensions exhibited the best (photo)electrocatalytic performance and could serve as a potential candidate for cost-effective and active electrode material. [ABSTRACT FROM AUTHOR]

Themechanism of the photoelectrochemical (PEC) effect of the corrosion products with semiconductor properties on the initial NaClinduced atmospheric corrosion of pure copper was studied in this work. The effect of UV illumination on the initial NaCl-induced atmospheric corrosion of pure copper was quantitatively studied using microgravimetry. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to identify the corrosion products and corrosion morphologies. Mott-Schottky methods were used to characterize the semiconductor type of the corrosion products. The photoinduced variations of the open circuit potentials, current densities, i-V curves and the polarization curves were used to analyze the PEC effect of the corrosion products with semiconductor properties on the corrosion of copper. UV illumination significantly increased the NaClinduced atmospheric corrosion rate of copper. The photoinduced electrons did not transfer to the copper substrate, on the contrary, the photogenerated holes captured the electrons from the copper substrate, thus accelerating the atmospheric corrosion process of pure copper. The detailed influencing mechanism of the PEC effect on the NaCl-induced atmospheric corrosion of copper was suggested in this paper. [ABSTRACT FROM AUTHOR]

The long-term photoelectrochemical cathodic protection by Co(OH)2-surface modified TiO2 of anatase nanotubes and rutile type, prepared by anodic oxidation has been studied in aqueous 3.5 wt% NaCl solution. Electrochemical measurements have been used to evaluate the photoelectrochemical protective properties of both Co(OH)2-modified TiO2 coupled with 304 stainless steel in 3.5 wt% NaCl solution under illumination and in the dark. Morphologies, crystal structures, surface compositions, and light response range of both Co(OH)2-surface modified TiO2 films before and after immersion were characterized, respectively, by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometry. The results show that the photogenerated electrode potential of both types of TiO2 films modified with Co(OH)2 is more negative affording protection of 304 stainless steel than that of the non-modified TiO2 under illumination. These TiO2 films provide a long period (12 h) of protection. The anatase-TiO2 nanotube film always shows a better protection performance than rutile-TiO2 film. [ABSTRACT FROM AUTHOR]

Colloidal core/shell quantum dots (QDs) have emerged as a promising light absorber for hydrogen (H 2) production in photoelectrochemical (PEC) cells due to their attractive optoelectronic properties. However, the unfavorable band alignment and lattice mismatch of core/shell materials lead to the sluggish separation/transfer of interfacial charges, challenging the large-scale utilization of QDs-based PEC systems. Herein, we report a unique synthetic approach that incorporates metal ions (Mn2+) into the lattice of heterostructured QDs in the process of shell growth, which is verified by the combined spectroscopic and electrochemical characterizations. The PEC cell based on the optimized QDs (Mn 0.03 -CdSe/CdS) exhibits a superior saturated photocurrent density (∼ 18.7 mA cm−2) to that of undoped CdSe/CdS QDs (∼ 9.6 mA cm−2) under one sun illumination. The introduced intragap states (4T 1) from Mn2+ ions not only reduce the conduction band offset between CdSe and CdS, but also suppress the non-radiative recombination process of photogenerated charges. This work provides a well-grounded guide to utilize metal ions for improving the transfer dynamics of photogenerated charges of heterostructured QDs in other optoelectronic devices. [Display omitted] • Mn2+ dopants are incorporated into the lattice of heterostructured CdSe/CdS QDs in the process of shell growth. • By controlling the concentration of Mn2+, the Mn 0.03 -CdSe/CdS QDs exhibits a superior saturated photocurrent density. • Utilize Mn2+ to improve the transfer rate of photogenerated charges between the core and shell interface. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL) in perovskite-based solar cells (PSCs) is attractive from the perspective of photon-to-electron conversion efficiency. TiO2thin film is preferred in situations where microstructure, stability and charge transport characteristics are important. In this regard, we illustrate an approach that involves the synthesis of TiO2–pepsin thin film that can be used either as a mesoporous or compact layer depending on the device architecture of PSC devices. It was observed that pepsin acts as organic glue to TiO2nanoparticles and facilitates in controlling morphology of the thin film. The addition of pepsin did not have any adverse effect on TiO2anatase phase. Thickness and roughness of mesoporous and compact TiO2thin film suggested that controlled agglomeration can be achieved by tuning the concentration of pepsin in the precursor colloidal solution. The spin-coated thin films indicated high bulk mobility (205 cm2V−1 s−1) and good thermal stability over a wide range temperature (25–700°C). Furthermore, in the presence of pepsin group in TiO2thin film, the inherent optical properties were retained, as confirmed by UV–vis analysis. [ABSTRACT FROM PUBLISHER]

In this article, we report the preparation of a novel 1D/2D TiO2NRs/BiOI NSs photoanode via a simple hydrothermal method followed by SILAR method. This facile synthesis route can simultaneously achieve uniform TiO2NRs/BiOI NSs composite nanostructures and obtain varied thick of BiOI NSs by controlling the SILAR cycles. The TiO2NRs/BiOI-3 (SILAR cycles of 15 cycles) heterojunction photoanode enhanced highest photocatalytic activity with a photocurrent density of 0·40 mA cm–2at 1·23 V versus RHE compared to pristine TiO2NRs photoanode at the same condition. It is demonstrated that the presence of BiOI NSs has played an important role in expanding the spectral response region and reduced photogenerated charges recombination rate. More importantly, the results provide new insights in the 1D/2D NRs/NSs composite structure served as photoanodes for PEC water splitting. [ABSTRACT FROM PUBLISHER]

TiO2 nanorod (TNR) arrays have been sensitized by CdS, PbS, CdS/PbS, and PbS/CdS quantum-dots (QDs). The TNR arrays were synthesized by a hydrothermal treatment, and QDs were deposited on the arrays by a successive ionic layer adsorption and reaction (SILAR) technique. The morphology, structure, composition, optical, photoelectrochemical (PEC), and photocatalytic (PC) properties were systematically investigated. The results demonstrate that TNR/QDs can effectively facilitate photoinduced carrier transport, suppress the recombination rate of electron-hole pairs, and improve the visible light absorption, PEC, and PC properties. The TNR/CdS(7)/PbS(3) sample shows the maximal photocurrent density (0.91 mA/cm²) and photodegradation efficiency (97.3%), which is nearly 37.9 and 2.89 times higher than those of bare TNR, respectively. The enhanced properties are attributed to the narrow band gaps and high absorption coefficients of QDs, and the type-II nanoheterostructures with a staggered alignment of band edges at the hetero-interface that can facilitate the spatial separation of electron-hole pairs. [ABSTRACT FROM AUTHOR]

Porous 4H-SiC layers were prepared from monocrystalline samples applying photo-electrochemical etching in hydrofluoric acid. The influence of both current and voltage controlled mode during photo-electrochemical porosification was investigated. It was found that the resulting degree of porosity, the homogeneity in porosity as well as the pore morphology mainly depend on the applied voltage, whereas the current level has an almost negligible impact on these important parameters. Based on these results, it is proposed that the formation of porous SiC during photo-electrochemical etching can be described by fractal growth. Finally the gathered knowledge allowed to detach the porous 4H-SiC layers, which comprised several sub-layers of alternating degree of porosity, from the 4H-SiC substrate. Such layers of tailored porosity are key components for several advanced device concepts such as optical filters or membranes for biological applications. [ABSTRACT FROM AUTHOR]

Global warming presents an ever-rising challenge to humans today, caused by an unprecedented rise in the carbon dioxide levels in the atmosphere over the past decade. This study proposes a way to fix this problem in a sustainable way using sunlight to convert CO2 into useful fuels through a novel device. A Simulink model of photo-voltaic cell, CO2 electrochemical reduction and photoelectrochemical reduction cell is developed and integrated together to model the device. The photo-voltaic cell model takes solar irradiation and temperature as inputs, giving electrical power as output. The CO2 electrochemical reduction cell model consists of three blocks, anode, cathode and voltage. Mole balances on anode and cathode give the product flow-rates. Nernst and Butler-Volmer equations calculate the voltage required to operate the CO2 reduction cell. The CO2 photo-electrochemical reduction cell calculates product flow rates and voltage required to operate the cell using continuity, charge balance and Butler-Volmer equations. The model of the integrated device calculates i-V characteristics of the photovoltaic, electrochemical reduction and photo-electrochemical reduction cell under different environmental conditions, the product flow rates, contribution of various cell over-voltages. The model developed predicts photo-electrochemical route to be more energy and area efficient as compared to the electrochemical route. [ABSTRACT FROM AUTHOR]

In this study, Cu-Ni/TiO 2 photocatalyst was synthesized using sol-gel coupled with hydrothermal followed by calcination. The effect of variation in calcination durations (60, 90, and 120 min) on solar hydrogen production was studied over Cu-Ni/TiO 2 photocatalyst in a photoelectrochemical (PEC) cell, connecting to a dye sensitized solar cell (DSSC) in series. The various techniques used for characterization of physicochemical and photoelectrochemical properties of photocatalysts. The 120 min calcined photocatalyst was the most effective photocatalyst with total produced hydrogen of 376.4 μmol/cm 2 compared to others. The physicochemical studies revealed that a better photocatalytic performance of 120 min calcined photocatalytic attributed to its high crystallinity, more absorbance in the visible region, reduction of grain boundaries, less bulk trapping center and surface state, and high Cu + :Cu 2+ ratio on the surface of the photocatalyst. This enhanced physicochemical properties reduced charge transfer resistance and increased the electron lifetime and photocurrent density as confirmed by electrochemical impedance spectroscopy (EIS) analysis. Furthermore, Mott-Schottky (M-S) analysis showed that the increase in calcination duration improved the flat band potential which facilitated efficient charge separation at the electrode/electrolyte interface with large carrier densities. [ABSTRACT FROM AUTHOR]

In this paper, the concept of using solid oxide photoelectrochemical cells (SOPCs) to split water at high temperature using visible sunlight was experimentally investigated, in order to search for the appropriate semiconductor materials. High temperature photoelectrochemical water splitting physically broadens the selection of potential applicable semiconductor materials and enables more visible sunlight absorption. This newly conceived concept provides a unique pathway for solar hydrogen production, compared to conventional photoelectrochemical cells (PECs) that require aqueous environments, though experimental validation is needed. The main focus of this study was on the fabrication and evaluation of high temperature diodes suitable for use as the photocatalytic/oxygen electrodes of SOPCs. The rectifying characteristics of TiO2based diodes, including Ag/TiO2, LSM/TiO2, LSC/TiO2, and LSCF/TiO2, were investigated at elevated temperatures. Among those diodes, only LSM/TiO2demonstrated acceptable rectifying properties up to 450°C, indicating that such configuration may be applicable to the proposed SOPC. The results also excluded Schottky diodes from the candidates due to their rapidly degrading rectifying behaviors at elevated temperatures. Candidate semiconductors for the photovoltaic (PV) part of the cell and electrolytes for the electrolysis part were also identified and summarized in this paper for future investigations. [ABSTRACT FROM AUTHOR]

Capability of reducing the overpotential and also increasing the current density of hydrogen evolution reaction, HER, through exposure to light can be aid in the development of effective HER driven by sunlight. With this in mind, herein, the hybrid electrode based on polypyrrole –CuS composite, PPyCuS, is fabricated with the aim to form an electrode photo-electrocatalyst for HER. Therefore, an in situ sonoelectrochemical method was employed to synthesis of hybrid nanocomposite film on copper substrate. The photoelectrochemical performance of PPyCuS@GOPt hetrostructure was investigated in acidic solution under visible light irradiation by linear sweep voltammetry, electrochemical impedance spectroscopy, EIS, and Tafel slopes evaluation. Actually, we could prepare the PPyCuS@GOPt nanocomposite film on Cu 2 O nano particles exhibited a much smaller onset overpotential with high current density for photo-HER. It was proven that GO, and Pt can act as effective dual co-catalysts to enhance the photocatalytic H 2 production activity of PPyCuS. The higher photoactivity is attributed to the fact that the photoinduced interfacial charge transfer in the heteronanostructures follow by further transfer in GO sheets. This work is expected to provide a new concept for development of highly efficient polymer-sulfide compounds photoelectrocatalysts for HER under simulated sunlight. [ABSTRACT FROM AUTHOR]

We report on the growth of porous Bi2MoO6 electrodes by first electrochemically depositing bismuth oxyiodide (BiOI) films and then thermally annealing the BiOI films with a molybdate solution. These Bi2MoO6 electrodes were tested as photoanodes for photoelectrochemical water oxidation. We found that the photoactivity of Bi2MoO6 electrode was largely improved after conducting a cyclic voltammetry treatment in 0.1 M phosphate buffer solution (pH 7.0). Through designed control experiments, XPS, FTIR and isoelectric point analyses, it was confirmed that phosphate anions (PO43-) modified the surface of Bi2MoO6 electrode during the cyclic voltammetry process and played a critical role in the enhancement of PEC performance. The performance improvement was attributed to the formation of a negative electrostatic field on the surface of Bi2MoO6 electrode after phosphate modification which resulted in the enhanced efficiency of charge separation. [ABSTRACT FROM AUTHOR]