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In this work, enhanced and selective photoelectrochemical (PEC) oxidation of atrazine was realized on molecular imprinted mesoporous TiO2 (MI-meso-TiO2). The investigation revealed that, for one hand, the surface MI sites could function as surface defects for accelerating the separation of photogenerated holes and electrons, leading to enhanced generation of hydroxyl radicals. For the other hand, the MI sites showed enhanced binding affinity toward atrazine, resulted from the formation of multiple hydrogen bonds and halogen bonds etc., which was testified by in situ ATR-FTIR spectra. It led to the enhanced adsorption and improved local concentration of atrazine on the electrode surface. Both the two factors contributed to the improved PEC oxidation activity for atrazine on MI-meso-TiO2 compared with that on meso-TiO2. Moreover, the high binding affinity between MI sites and atrazine resulted in the selective recognition ability toward atrazine in the presence of the coexisting pollutants, so that selective PEC oxidation of atrazine in complex polluted water samples was successfully achieved on MI-meso-TiO2 with the apparent rate constant of 0.25 h−1, whereas that on meso-TiO2 was only 0.08 h−1. This work provided something new for explaining the selective and enhanced PEC performance on molecular imprinting catalyst.

Refractory nitride plasmonics offer the potential to realize enhanced light–matter interactions for energy harvesting and photo-driven chemistry with materials systems that are thermally rugged, inexpensive, and potentially catalytic. Here, we have embedded commercial and in-house synthesized titanium nitride (TiN) nanoparticles (NPs) into matrices of titanium dioxide (TiO2) and compared their ability to enhance electrochemical oxidation reactions to that of conventional gold (Au) NPs. Although the photon-to-carrier conversion efficiencies were low (∼10–4%), the reaction rates were enhanced by a factor of 4 in the visible and near-infrared (IR) regions for both Au and TiN compared to a pure TiO2 control, with TiN showing an order of magnitude improvement over Au in the near-IR region. The spectral dependence of reaction rate enhancement followed the NP extinction spectra, and a linear power dependence identifies a photoexcited carrier mechanism (i.e., decaying plasmons excite carriers that participate in ...

It is highly profitable to transform glycerol – the main by-product from biodiesel production to high value-added chemicals. In this work, we develop a photoelectrochemical system based on nanoporous BiVO4 for selective oxidation of glycerol to 1,3-dihydroxyacetone – one of the most valuable derivatives of glycerol. Under AM 1.5G front illumination (100 mW cm−2) in an acidic medium (pH = 2) without adscititious oxidant, the nanoporous BiVO4 photoanode achieves a glycerol oxidation photocurrent density of 3.7 mA cm−2 at a potential of 1.2 V versus RHE with 51% 1,3-dihydroxyacetone selectivity, equivalent to a production rate of 200 mmol of 1,3-dihydroxyacetone per m2 of illumination area in one hour., The selective conversion of inexpensive precursors to high-value chemicals presents valuable academic and industrial consequences. Here, the authors show bismuth vanadate photoanodes to utilize light and photoelectrochemically oxidize glycerol selectively to valuable industrial products.

Conductive polymers are widely used as active and auxiliary materials for organic photovoltaic cells due to their easily tunable properties, high electronic conductivity, and light absorption. Several conductive polymers show the cathodic photogalvanic effect in pristine state. Recently, photoelectrochemical oxygen reduction has been demonstrated for nickel complexes of Salen-type ligands. Herein, we report an unexpected inversion of the photogalvanic effect caused by doping of the NiSalen polymers with anionic porphyrins. The observed effect was studied by means of UV-Vis spectroscopy, cyclic voltammetry and chopped light chronoamperometry. While pristine NiSalens exhibit cathodic photopolarization, doping with porphyrins inverts the polarization. As a result, photoelectrochemical oxidation of the ascorbate proceeds smoothly on the NiSalen electrode doped with zinc porphyrins. The highest photocurrents were observed on NiSalen polymer with o-phenylene imine bridge, doped with anionic zinc porphyrin. Assuming this, porphyrin serves both as a catalytic center for the oxidation of ascorbate and an internal electron donor, facilitating the photoinduced charge transport and anodic depolarization.

Here, we report the immobilization of Co-protoporphyrin IX (Co-PPIX) substituted cytochrome c (Co-cyt c) on Antimony-doped Tin Oxide (ATO) as a catalyst for photoelectrochemical oxidation of water. Under visible light irradiation (λ &gt, 450 nm), the ATO-Co-cyt c photoanode displays ~6-fold enhancement in photocurrent density relative to ATO-Co-PPIX at 0.25 V vs. RHE at pH 5.0. The light-induced water oxidation activity of the system was demonstrated by detecting evolved stoichiometric oxygen by gas chromatography, and incident photon to current efficiency was measured as 4.1% at 450 nm. The faradaic efficiency for the generated oxygen was 97%, with a 671 turnover number (TON) for oxygen. The current density had a slow decay over the course of 6 h of constant irradiation and applied potential, which exhibits the robustness of catalyst-ATO interaction.

Recirculating air purification technologies are employed as potential means of reducing exposure to aerosol particles and airborne viruses. Toward improved testing of recirculating air purification units, we developed and applied a medium‐scale single‐pass wind tunnel test to examine the size‐dependent collection of particles and the collection and inactivation of viable bovine coronavirus (BCoV, a betacoronavirus), porcine respiratory coronavirus (PRCV, an alphacoronavirus), and influenza A virus (IAV), by a commercial air purification unit. The tested unit, the Molekule Air Mini, incorporates a MERV 16 filter as well as a photoelectrochemical oxidating layer. It was found to have a collection efficiency above 95.8% for all tested particle diameters and flow rates, with collection efficiencies above 99% for supermicrometer particles with the minimum collection efficiency for particles smaller than 100 nm. For all three tested viruses, the physical tracer‐based log reduction was near 2.0 (99% removal). Conversely, the viable virus log reductions were found to be near 4.0 for IAV, 3.0 for BCoV, and 2.5 for PRCV, suggesting additional inactivation in a virus family‐ and genus‐specific manner. In total, this work describes a suite of test methods which can be used to rigorously evaluate the efficacy of recirculating air purification technologies.

Photoelectrochemical approaches are finding use in the transformation of organic molecules beyond water oxidation and CO2 reduction. Among the different reactions that can be performed, the selective oxidation of alcohols to aldehydes is a transformation of great interest, as aldehydes are the starting materials for the preparation of more complex organic molecules with high added value. In order to develop efficient photoelectrochemical methodologies for this reaction, it is crucial to reveal all the different parameters that are involved in such light-driven processes. Herein we analyse in detail the effect of the light wavelength and atmosphere on the photoelectrochemical oxidation of benzyl alcohol to benzaldehyde using BiVO4 electrodes. Our studies demonstrate that an important contribution to the oxidation of alcohol is due to UV light-induced production of singlet oxygen, which is also responsible for the formation of hydrogen peroxide in the reaction media. These findings are key for identifying and evaluating the underlying mechanism involved in this type of photoelectrochemically induced oxidation, in order to avoid misinterpretations of the efficiencies.

Heterogeneous photocatalytic water oxidation is a promising system for sustainable and competitive solar fuel production since 1972, discovered by Fujishima and Honda using TiO2 semiconductor (SC). Despite the good stability issue of the TiO2 material, it can separate the charge carriers only under UV light from the valence band (VB) to the conduction band due to high bandgap energy. Visible light–active n-type Bi-based metal oxides are considered as stable, efficient SCs to oxidize water and degrade pollutants because of the favorable band energy positions: particularly the VB energy as well as visible light activity of the material. These metal oxides are of low production cost, less toxicity, and easily soluble with other elements, resulting in a large family of solid solution compounds. In this chapter, the synthesis and characteristics of Bi-based simple oxides obtained through various routes for different photoelectrochemical applications is being explored. Effects of different synthetic routes, structure, surface morphology, modifying agents, etc. on their performance are being discussed in detail.

Abstract Dye-sensitized photoelectrochemical cells represent an appealing solution for artificial photosynthesis, aimed at the conversion of solar light into fuels or commodity chemicals. Extensive efforts have been directed towards the development of photoelectrodes combining semiconductor materials and organic dyes; the use of molecular components allows to tune the absorption and redox properties of the material. Recently, we have reported the use of a class of pentacyclic quinoid organic dyes (KuQuinone) chemisorbed onto semiconducting tin oxide as photoanodes for water oxidation. In this work, we investigate the effect of the SnO2 semiconductor thickness and morphology and of the dye-anchoring group on the photoelectrochemical performance of the electrodes. The optimized materials are mesoporous SnO2 layers with 2.5 μm film thickness combined with a KuQuinone dye with a 3-carboxylpropyl-anchoring chain: these electrodes achieve light-harvesting efficiency of 93% at the maximum absorption wavelength of 533 nm, and photocurrent density J up to 350 μA/cm2 in the photoelectrochemical oxidation of ascorbate, although with a limited incident photon-to-current efficiency of 0.075%. Calculations based on the density functional theory (DFT) support the role of the reduced species of the KuQuinone dye via a proton-coupled electron transfer as the competent species involved in the electron transfer to the tin oxide semiconductor. Finally, a preliminary investigation of the photoelectrodes towards benzyl alcohol oxidation is presented, achieving photocurrent density up to 90 μA/cm2 in acetonitrile in the presence of N-hydroxysuccinimide and pyridine as redox mediator and base, respectively. These results support the possibility of using molecular-based materials in synthetic photoelectrochemistry. Graphic abstract

Metal–organic frameworks (MOFs) provide a suitable platform for stable and efficient heterogeneous photoelectrochemical oxidation catalysis due to their highly ordered structure, large surface area, and synthetic tunability. Herein, a mixed-linker MOF comprising of a photosensitizer [Ru(dcbpy)(bpy)2]2+ (bpy = 2,2′-bipyridine, dcbpy = 5,5′-dicarboxy-2,2′-bipyridine) and catalyst [Ru(tpy)(dcbpy)Cl]+ (tpy = 2,2′:6′,2′′-terpyridine) that were incorporated into the UiO-67 framework and grown as thin films on a TiO2-coated, fluorine-doped tin oxide (FTO) electrode (RuB-RuTB-UiO-67/TiO2/FTO). When used as an electrode for the photoelectrochemical oxidation of benzyl alcohol, the mixed-linker MOF film showed a faradaic efficiency of 34%, corresponding to a 3-fold increase in efficiency relative to the RuB-UiO-67/TiO2/FTO control. This increase in catalytic efficiency is ascribed to the activation of RuTB moieties via oxidation by photogenerated RuIIIB. Transient absorption spectroscopy revealed the delayed appearance of RuIIITB* or RuIIITB formation, occurring with a lifetime of 21 ns, due to energy and/or electron transfer. The recovery kinetics of the charge separated state was increased (283 μs) in comparison to single-component control experiments (105 μs for RuB-UiO-67/TiO2/FTO and 7 μs for RuTB-UiO-67/TiO2/FTO) indicating a cooperative effect that could be exploited in chromophore/catalyst MOF motifs.

Photoelectrochemical oxidation of water presents a pathway for sustainable production of hydrogen peroxide (H2O2). Two-electron water oxidation toward H2O2, however, competes with the popular four-electron process to form oxygen and one-electron water oxidation to form OH radical. To date, bismuth vanadate (BiVO4) has been shown to exhibit promising selectivity toward H2O2, especially under illumination, but it suffers from high overpotential and notoriously poor stability. Herein, using density functional theory calculations, we predict that doping BiVO4 with optimal concentrations of gadolinium (Gd) not only enhances its activity for H2O2 production but also improves its stability. Experimentally, we demonstrate that intermediate amounts of Gd doping (6–12%) reduce the onset potential of BiVO4 for H2O2 production by ∼110 mV while achieving a Faradaic efficiency of ∼99.5% under illumination and prolonging the catalytic lifetime by more than a factor of 20 at 2.0 V vs RHE under illumination.

In this research, by means of electrochemical cyclic voltammetries (CVs), the pathways of charge carrier interfacial transfer (IT) from TiO2 and Au/TiO2 rutile nanorod (NR) arrays to electrolyte were studied. For pure TiO2, the electron IT to O2 takes place via both the conduction band (CB) states and the surface states (SS). The UV light illumination increases the electron IT via CB states, but inhibits that via SS pathway. The CV results also evidenced that the Au nanoparticles (NPs) on TiO2 surface play dual roles of electron storage and electron IT pathway. Our results showed that the Au-induced defects, locating at Au/TiO2 perimeter, form an important additional pathway for electron IT to O2. UV light illumination increases the electron IT via Au NPs and Au-induced SS. In addition, we also revealed a special IT pathway of hot holes via the Au/TiO2 perimeter contributes to the full water oxidation under visible light illumination. Therefore, the Au/TiO2 perimeter region plays dual roles in the IT of both electrons and holes. Basing on these results, the IT pathways of charge carriers in Au/TiO2 were illustrated from the viewpoint of energy band diagram. The photocatalytic degradation of methyl orange, photoelectrochemical oxidation of water, and photogeneration of free hydroxyl radicals ( OH) were studied under UV and visible light illuminations. The association between the charge carrier IT pathways and the photocatalytic properties was also discussed.

The photoelectrochemical removal of phenol from aqueous solution under solar light with polyaniline-modified TiO2 electrodes has been investigated. Nanotubular TiO2 electrodes (NTs) have been obtained by anodization of Ti; the coating with polyaniline (PANI) has been obtained with a three-step approach: (i) functionalization of NTs by electroreduction of 4-nitrobenzendiazonium salt, (ii) electrochemical reduction of the nitro group to amine, (iii) galvanostatic electropolymerisation of aniline. The results of galvanostatic electrolyses under simulated solar light are presented, degradation of phenol with TiO2 was achieved and the trends of concentration with time follow a pseudo-first order kinetics. As a comparison, also unmodified NTs have been tested. The results depend on the initial concentration of reactant, with 300 mg dm−3 of phenol and applying a current density i = 0.18 mA cm−2, the reaction rate with NT-PANI was more than double of that obtained with NTs. Moreover, the presence of PANI increases the conductivity of the electrode, which in turn depolarizes the cell. Hydroquinone and oxalic acid have been detected as main intermediates, which are distributed depending on the experimental conditions and kind of electrodes: the relevant data have been modelled assuming an in-series reaction scheme and pseudo first order kinetics.

This work focuses on the scale-up of irradiated-assisted electrochemical processes with diamond anodes for the removal of clopyralid from washing soil wastes. In particular, it is studied the influence of the ratio electrochemical power/total power in the performance of conductive diamond photoelectrochemical oxidation (CDPEO) and conductive diamond sonoelectrochemical oxidation (CDSEO) at high and low ultrasounds frequencies. The comparison is carried out in terms of mineralization, clopyralid decay, reaction intermediates and inorganic speciation. The CDPEO-7.7 W tests carried out in a single cell and in a stack of cells show that the stack seems to be less efficient in terms of clopyralid removal and mineralization than the single cell. The ratio electrochemical energy/photoelectrochemical energy is more favorable in small devices, where the photolytic energy is not only a complement but a primary treatment. Regarding inorganic speciation, chloro-species show a similar behavior in absence and presence of US or UV irradiation. Opposite, irradiation seems to inhibit the reduction of nitrate to ammonium, independently on the irradiation power used. In terms of energy efficiency, an increase of the radiation power does not entail a high efficiency/energy consumption ratio, and CDPEO-7.7 W and CDSEO-24 kHz-100 W show efficiency/energy consumption ratios 3.7 and 2.3 times higher than that of CDSEO-10 MHz-450 W.

A method for the preparation of film coatings of titania doped with bismuth (Bi3+) and lead (Pb2+) ions, separately and simultaneously, has been developed based on sol–gel synthesis. According to X-ray phase analysis, the films represent a single-phase system of titania in anatase modification. It has been shown that doping of titania with bismuth and lead leads to a shift of the absorption maximum to the visible light region; in this case, the largest shift is observed in the sample containing 2.5 wt % bismuth and lead. The film coatings have been studied as catalysts of photoelectrooxidation of methanol, formic acid, and phenol. It has been shown that the highest catalytic effect is observed for the samples containing simultaneously bismuth and lead; however, doping of titania with bismuth has the greatest effect on the rate of organic substrates oxidation. It has been assumed that photoelectrochemical oxidation of the model systems with visible light is due to a decrease in the band gap of doped titania to 2.7 eV.

We report the photoelectrochemical (PEC) oxidation of glucose at tungsten trioxide nanoplate (WO3NP) electrode for glucose sensing application and photo fuel cell (PFC) application. The WO3-based PEC sensor shows high sensitivity of 68.15 μA cm−2 mM−1 in glucose detection for the concentrations in the range of 0.1~0.5 mM and displays good selectivity toward the interferents of ascorbic acid (AA) and uric acid (UA). Moreover, electricity can be extracted from photo-oxidizing of glucose on WO3NP electrode in a PFC device and the output strongly depends on the concentration of glucose fuel. In addition, the power performance of PFC obtained under irradiation shows 60-fold higher than that of achieved in the dark, indicating that photo-oxidation of glucose on the WO3NP anode is the essence for this fuel cell electricity generation. The work expands the application of WO3 in the field of glucose analysis and provides a possible way to detect glucose without inputting external power.

Developing new methods to use visible light is important for TiO2 photocatalysis. This research reported that the TiO2 rutile nanorod (NR) array shows high sub-band gap visible light response. By means of electrochemical cyclic voltammetries, the intrinsic occupied gap states of TiO2 NR array were identified. It was seen that the gap states can be switched from filled states to empty states by visible light illumination, which play the role of relay in promoting electrons from the valence band to the conduction band of TiO2 NRs after absorbing two visible photons. In a consequence, the TiO2 NR array shows the obvious anodic photocurrents for water photoelectrochemical oxidation and the photocatalytic degradation of methyl orange under visible light illumination. This study revealed the significance of the deep occupied gap states of TiO2 NR arrays, which are usually considered as recombination centers. Different from conventional photocatalysis arising from inter-band electron transition, the present research shows a different pathway to use visible light in TiO2 photocatalysis effectively, which should be highly meaningful for designing visibly-active TiO2 photocatalysts.

A novel polishing method, photoelectrochemical mechanical polishing (PECMP), is proposed for finishing the n-type gallium nitride semiconductor wafers. The method applies the ultraviolet-light irradiation to a wafer surface to generate unpaired electron-holes during a mechanical polishing process. The free-holes facilitate photoelectrochemical oxidation so as to accelerate material removal in the polishing process. The novel method achieves a material removal rate of 1.2 μm/h which is one order of magnitude higher than that of a conventional technique. In addition, the method removes the surface and subsurface damages induced in a previous machining process and obtains an atomically flat and damage-free wafer surface.

Here we report on an advanced photoelectrochemical (PEC) oxidation of 22 phenolic pollutants based on modified nanoporous TiO2, which was directly grown on a titanium substrate electrochemically. Their degradation rate constants were experimentally determined and their physicochemical properties were computaionally calculated. The quantitative structure–property relationship (QSPR) was elucidated by employing multiple linear regression (MLR) method. A supervised machine learning approach was employed to build QSPR models. The high predictive abilities of the QSPR model were validated via leave-one-out (LOO) method and a strict regimen of statistical validation tests. The significant descriptors identified in the QSPR Model for the phenolic compounds were also assessed using a typical dye pollutant Rhodamine B, further confirming the high effectiveness and predictability of the optimized model. Our study has shown that the integrated effect of the structural, hydrophobic and topological properties along with electronic property should be considered in order to design an efficient PEC catalytic approach for environmental applications.

Herein, we report shape-dependent photoelectrocatalytic activity of Ag/Ag2O nanostructures supported on pristine or nitrogen-doped TiO2 (NTiO2). Isotropic (spherical) and anisotropic (cubic and triangular) nanocrystals of Ag/Ag2O nanocrystals were fabricated using complexing and surface directing agents. Microscopic images confirmed the formation of nanospheres (∼ 50–60 nm), nanocubes (∼ 50–70 nm), triangular nanoplates (∼ 40–60 nm). The X-ray photoelectron spectroscopy indicated the presence of metallic silver (Ag0) and oxidized silver (Ag+). The as-prepared photoelectrodes were illuminated by Ultraviolet–Visible (λ = 300–600 nm) or visible radiations (λ = > 420 nm), and photoelectrochemical oxidation of water was examined. The findings indicate a significant correlation in the shape of Ag/Ag2O nanostructures, the incident wavelength, and the photoelectrochemical performance. In addition, different performance trend was discerned under Ultraviolet–Visible and visible excitations with respect to the amount of deposited Ag/Ag2O. The variation in activity observed with different shapes of Ag/Ag2O was correlated to enhanced optical property, arising due to the anisotropic structure, and electrical conductivity.

Small-molecule organic semiconductors exhibit great potential for the photoelectrochemical oxidation of water because of their n-type semiconductor nature and their tunable bandgaps. In this work, several head-to-tail bis-coumarins were synthesized and their photophysical properties characterized. Their characteristics as n-type semiconductors were modified by varying the electronic character of substituents at positions 1 and 7, which enabled the energy level of the LUMO and the photoinduced charge-carrier-transfer efficiency to be modulated. X-Ray absorption near-edge structure (XANES) spectroscopy confirmed that the charge transfer is a crucial factor contributing to the resulting activity of the photoanode. The photoactivity of the photoanodes towards water oxidation was revealed to be governed by both the LUMO energy level and transfer efficiency of the photoinduced charge carriers. Among the studied molecules, a bis-coumarin with benzothiophenyl substituents showed the greatest potential as light absorber for photoelectrochemical water oxidation.

Zinc lanthanum tantalum oxynitride [ZnLaTaON2] powders were synthesized by conventional solid state reaction. ZnLaTaON2 photoelectrodes were prepared by electrophoretic deposition of ZnLaTaON2 suspension in acetone onto ITO substrate. The photoelectrodes of ZnLaTaON2 were established to reveal photoelectrochemical properties for water oxidation reaction. Moreover, a cobalt phosphate (Co-Pi) was loaded on ZnLaTaON2 photoelectrodes via photodeposition method to enhance the photoelectrochemical water oxidation performances. Photocurrent voltage characteristics of the Co-Pi/ZnLaTaON2 photoelectrodes were enhanced with its effect which is more evidenced at lower water oxidation potentials. A relatively stable photocurrent density of 5 mA/cm2 at 1.5 V vs RHE was attained with the support of electron donor in alkaline phosphate solution. Comparatively, in Co-Pi/ZnLaTaON2 photoelectrodes, approximately threefold enhancement was noticed at 1.8 VRHE in assessment with parent photoelectrode. On the other hand, Co-Pi/ZnLaTaON2 photoelectrodes have been shown as an alternative pathway to improve the photoelectrochemical current gain through the PEC water oxidation reaction.

The photoelectrochemical oxidation of bovine serum albumin (BSA) at a cadmium sulfide/titanium dioxide (CdS/TiO2) electrode and its influences on the photoelectrocatalytic oxidation of ascorbate (AA) have been investigated by combining a photocatalytic fuel cell. The UV-excited BSA/CdS/TiO2 electrode exhibits direct oxidation peaks related to tryptophan (Trp) and other amino acid residues. The oxidation products of Trp on CdS/TiO2 electrode exhibit a pair of well-defined quinonyl/hydroquinonyl-based redox peaks at the formal potential of 0.025 V (vs. SCE) controlled by surface-confined electrochemical processes. The BSA oxidation photocurrent linearly increases with increasing BSA or O2 concentration. The AA oxidation is dependent on the UV irradiation, BSA concentration and photoanode materials. An appropriate amount of BSA leads to a 58% increase in the photocurrent response of AA oxidation on the CdS/TiO2 electrode, and a 0.5-fold increase in the maximum power density of the proposed photocatalytic AA/O2 fuel cell employing palladium(II) porphyrin Pd(II)TCPP (TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin) modified carbon felt cathode. The present results provide a new platform for evaluating the effects of serum albumin on the antioxidative action of AA in the absence and presence of UV irradiation.

We demonstrate for the first time the application of p-NiFe2O4/n-Fe2O3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe2O4/n-Fe2O3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe2O4 and Fe2O3) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe2O4/n-Fe2O3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured p-NiFe2O4/n-Fe2O3 device with equal molar 1:1 ratio of NiFe2O4 and Fe2O3 was found to be highly efficient for PEC water oxidation as compared with pure hematite, 1:2 and 1:3 molar ratios of composite. The photocurrent density of 1:1 composite thin film on planar substrate was equal to 1.07 mA/cm2 at 1.23 VRHE, which was 1.7 time...

Ti/TiO2-NTs/Sb-SnO2 electrode was prepared by gradient pulsed electrodeposition, and its electrochemical properties were evaluated. The catalytic activity and reusability of the electrode were tested by electrochemical oxidation (EO) and photoelectrochemical oxidation (PEO) of organics present in textile industry wastewater (TWW) and coffee bean processing industry wastewater (CWW). COD removal of ~ 41% was achieved after 5-h electrolysis under a constant applied current density of 30 mA cm−2 for TWW and 50 mA cm−2 for CWW. Nearly 14 and 18% increment in COD removal was observed under PEO for TWW and CWW, respectively. The turbidity of TWW reduced from 15 to ~ 3 NTU and the turbidity of CWW reduced from 27 to ~ 3 NTU by both EO and PEO. The % COD removal observed after 5-h electrolysis remained consistent for 7 repeated cycles; however, the catalytic activity of the electrode reduced gradually. These results suggested that the Ti/TiO2-NTs/Sb-SnO2 can be a potential electrode for the treatment of industrial wastewater.

In this paper, high performance quadruple gate-embedded T structured GaN-based metal–oxide–semiconductor high-electron mobility transistors (MOSHEMTs) were fabricated using laser interference photolithography method and photoelectrochemical oxidation method, in which polymethylmethacrylate was used as sacrificial layer. The associated drain-source saturation current was improved to 175 mA/mm and the gate leakage current at the gate-source voltage of −80 V was improved to $0.81~\mu \text{A}$ compared with the 125 mA/mm and $7.6~\mu \text{A}$ of the conventional single gate GaN-based MOSHEMTs, respectively. Moreover, the associated maximum extrinsic transconductance of the quadruple gate-embedded T structured GaN-based MOSHEMTs was enhanced from 97.3 mS/mm to 118.4 mS/mm. Besides, the associated unit gain cutoff frequency and the associated maximum oscillation frequency were improved from 7.6 GHz to 10.8 GHz and from 11.4 GHz to 27.4 GHz, respectively. The improved performances of the quadruple gate-embedded T structure GaN-based MOSHEMTs were attributed to the function of the gate length reduction and the gate resistance decrease.

In this paper, the multiple-submicron channel array gate-recessed AlGaN/GaN fin-metal-oxide-semiconductor high-electron mobility transistors (fin-MOSHEMTs) were fabricated using the photoelectrochemical oxidation method, the photoelectrochemical etching method, and the He-Cd laser interference photolithography method. The multiple-submicron channel array was formed using the He-Cd laser interference photolithography system. The gate-recessed structure and the directly grown gate oxide layer were performed using the photoelectrochemical etching method and the photoelectrochemical oxidation method, respectively. The subthreshold swing and the extrinsic transconductance were improved in the resulting devices with a narrower channel width. Furthermore, the unit gain cutoff frequency and the maximum oscillation frequency were also enhanced using a narrower channel width in the multiple-submicron channel array AlGaN/GaN fin-MOSHEMTs.

The modification of a BiVO4/WO3 photoelectrode with Al2O3 by a chemical vapor deposition (CVD) method significantly improved the faradaic efficiency for H2O2 production (FE(H2O2)) in the photoelectrochemical oxidation of H2O. The faradaic efficiency after passing 0.9 C (after photoirradiation for 15 min using simulated solar light) was 80% using a 2.0 M KHCO3 aqueous solution as an electrolyte. The initial FE(H2O2) (

From solutions of organic precursors, nanosized films of titanium dioxide with photoelectrochemical activity in the visible region are obtained. A possibility of photoelectrochemical oxidation of a number of organic compounds under illumination with monochromatic light at a wavelength of 464 nm is demonstrated, which may be due to a decrease in the n-TiO2 band-gap energy to 2.7 eV.

The SnO 2 -Sb 2 O 4 (MMO) and SnO 2 -Sb 2 O 4 -WO 3 (MMO-WO 3 ) electrodes were prepared by electrodeposition followed by dip coating and characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. The electrochemical (EC) and photoelectrochemical (PEC) degradation studies were carried out on trypan blue (TB) dye. These studies revealed that the characteristics and performance of MMO electrode improved significantly on nano-WO 3 modification. The oxygen evolution potential (OEP) increased from 2.07 V (vs Ag/AgCl) to 2.21 V and the accelerated service life increased by 1.7 times. 88 and 93% color removal was achieved on electrolysis for 240 min using MMO electrode; whereas, 100% color removal was achieved within 120 min by both EC and PEC using MMO-WO 3 . The percentage chemical oxygen demand (COD) removal achieved using MMO electrode by EC and PEC were only 60 and 63% respectively; whereas, it increased to 78 and 84% with MMO-WO 3 electrode. A probable pathway for TB degradation was proposed on the basis of liquid chromatography–mass spectrometry (LC–MS) analysis and quantum chemical calculations were performed on TB molecule to corroborate the proposed degradation pathway.

The photo-assisted electrochemical oxidation of benzylic alcohol derivatives was achieved with excellent yields up to 97% at low applied potential under visible light irradiation (>420 nm) using a BiVO₄/WO₃ photoelectrode in aprotic organic media. The faradaic efficiencies for oxidation of 1-phenylethyl alcohol was very high (>99%) in 0.1 M Bu₄NBF₄/MeCN. The applied potentials for the oxidation of benzylic alcohols (approximately +0.7 V vs. SHE) were considerably lower than those of the Pt electrodes (approximately +1.9 V vs. SHE). The turnover number of moles of oxidation product per moles of BiVO₄ was approximately 1200.

Sn x -W (100-x) -oxide coatings (x = 0, 20, 40, 60, 80 and 100) doped with Sb (∼3 at.%) were formed on a Ti substrate by a thermal deposition method in order to evaluate their potential use as electrodes for the photoelectrochemical oxidation of organic compounds. Surface microstructure/morphology and chemical composition of the coatings, as well as their photoelectrocatalytic activities were investigated using electrochemical and surface-characterization techniques. It was found that the surface roughness of the coatings depends on their composition, yielding an average value of R a = 1.1 ± 0.5 μm. The band gap energy was found to be independent on the coating composition up to the relative W/Sn at. ratio of 4/6, yielding an average value of 3.53 ± 0.05 eV (which corresponds to the band gap of doped SnO 2 ), but then it decreased for the three coatings with the highest W content, to an average value of 2.56 ± 0.10 eV (which corresponds to the value of pure WO 3 ). All the coatings were found to be photoactive under the anodic bias. Further, all the coatings were found to be photoelectrochemically active towards the degradation of phenol red dye solution under UV light irradiation. The intrinsic photoelectrocatalytic activity was found to be highest for the Sn 80% -W 20% -oxide electrode coating.

In this work, we study the role of nanotextured ZnFe2O4/Fe2O3composite thin films fabricated by ultrasonic spray pyrolysis (USP) on the photoelectrochemical water oxidation reactions. The ZnFe2O4/Fe2O3 composites with different molar ratios are deposited on three-dimensional nanospikes (NSP) substrate, and the results are compared with those for planar devices. It is observed that optical absorption and charge separation due to larger surface area is significantly enhanced in nanotextured photoactive ZnFe2O4/Fe2O3 films. After characterization of ZnFe2O4/Fe2O3 composite films with different molar ratios (ZF1, ZF2, and ZF3), we find that the nanotextured ZF1 composite with a molar ratio of 1:1 has the highest activity with photocurrent density of 2.19 mA/cm2 in photoelectrochemical oxidation of water. This photocurrent density is 3.4 and 2.73 times higher than the photocurrent density values of pure hematite on planar fluorine-doped tin oxide (FTO) coated glass and the highest reported value of ZnFe2O4/Fe2...

The present work has studied renewable hydrogen production by photoelectrocatalytic degradation of model organic substances representing biomass derived organic wastes. Its purpose was to show that renewable energy can be produced by consuming wastes. The study has been carried out by employing nanoparticulate WO3 photoanodes in the presence of ethanol, glycerol or sorbitol, i.e. three substances which are among typical biomass products. In these substances, the molecular weight and the number of hydroxyl groups increases from ethanol to sorbitol. The photocurrent produced by the cell was the highest in the presence of ethanol, smaller in the case of glycerol and further decreased in the presence of sorbitol. The photocurrent was roughly the double of that produced in the absence of an organic additive thus demonstrating current doubling phenomena. Hydrogen was produced only under illumination and was monitored at two forward bias, 0.8 and 1.6V vs Ag/AgCl. Hydrogen production rates followed the same order as the photocurrent thus indicating that hydrogen production by reduction of protons mainly depends on the current flowing through the external circuit connecting photoanode with cathode. The maximum solar-to-hydrogen efficiency reached by the present system was 2.35%.

Copper (II) tungstate (CuWO 4 ) has better light absorption and selectivity for a photochemical water-splitting reaction than those of its binary oxide counterpart. In this work, we report a facile single-step hydrothermal method to grow CuWO 4 with a bitter gourd shape directly on a transparent conductive substrate for the first time. CuWO 4 was synthesized via the condensation of a stable aqueous precursor solution of peroxopolytungstic acid and a copper precursor. The proposed method uniformly deposited CuWO 4 on fluorine-doped tin oxide with strong adhesion. The obtained CuWO 4 films showed a superior photocurrent density of 0.6 mA/cm 2 at 1.23 V vs. a reversible hydrogen electrode in a 0.1 M Na 2 SO 4 electrolyte, which was relatively higher than the values recently reported for CuWO 4 photoanodes. The optimized CuWO 4 exhibited an incident photon-to-current conversion efficiency of 30% at 350 nm for the photoelectrochemical oxidation of water. An X-ray photoelectron spectroscopy valence band edge analysis revealed an increase in the valence band edge position in the CuWO 4 , along with a decrease in the band gap compared to those in WO 3 . The procedure proposed here provides a promising approach for the design of an efficient CuWO 4 photoanode for water splitting.

Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe2 O3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm-2 ), a maximal photocurrent of 1.0 mA cm-2 is achieved with ZnO/Fe2 O3 core-shell NWs and 2.3 mA cm-2 was achieved for the PH3 -treated NWs at 1.23 V versus RHE. The PH3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe2 PO5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material.

A high-quality polycrystalline bismuth vanadate (BiVO 4 ) film was prepared on a fluorine-doped tin oxide substrate via a facile two-step strategy involving electrodeposition and annealing processes. The morphology and structural characterization of the resulting film were investigated by different methods including scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared, ultraviolet-visible (UV-vis) absorption, and Raman spectroscopies. XRD patterns as well as optical measurements revealed that BiVO 4 film crystallized with a pure monoclinic scheelite structure. The prepared BiVO 4 film was used for heterogeneous oxidation of chlorate ions in aqueous solution via electrochemical (EC), photochemical (PC), and photoelectrochemical (PEC) processes. The decrease in concentration of chlorate was monitored using UV-vis absorption spectroscopy. The results revealed that BiVO 4 could effectively perform chlorate oxidation under light irradiation through a PEC method. The kinetics of chlorate oxidation was consistent with a first-order reaction, and the rate constant for the PEC process was found to be much higher than those of EC and PC. Furthermore, a possible photocatalytic oxidation mechanism for chlorate mainly based on the formation of perchlorate ions is proposed.