Photoelectrochemical Behavior Research Articles

Sequence-Controlled Electrochemical Immobilization of Catalyst-Photosensitizer Oligomers for Tuning Photoelectrochemical Behaviors

Sequence-Controlled Electrochemical Immobilization of Catalyst-Photosensitizer Oligomers for Tuning Photoelectrochemical Behaviors

(Vittorio de Nora Award) When Solid State Semiconductor Physics and Devices Meet Photoelectrochemistry: From Growth and Interfacial Processes to Photovoltaics

I joined the CNRS solid-state physics laboratory near Paris in 1978, to work on the preparation of CdTe solar cells using close space sublimation (CSS) growth process. Thanks to some original discoveries, we were able to achieve a record yield of 10.5% for the time, but this research was gradually abandoned in France and in Europe. Yet it was this method that formed the basis of the technology developed with such success by first solar. So I was on the right track.However, it was in a different direction that I decided to go: semiconductor photoelectrochemistry, a rapidly developing field at the time. Here too, solar energy remained the backdrop, with the field opened up by Honda’s work on the photoelectrolysis of water. I thus began research into the mechanisms of charge transfer at semiconductor-electrolyte interfaces, keeping CdTe as my study material, enabling me to draw on my knowledge of solid-state devices to guide the analysis of its photoelectrochemical behavior in an original way. Our studies have focused on highlighting the energetic changes at interfaces under illumination during charge transfer reactions towards redox species in competition with corrosion reactions. We have demonstrated the role of adsorption and surface chemistry in these phenomena, with the result that photoelectrochemical properties can be optimized. Photoelectrochemistry is once again a highly topical field with artificial photosynthesis.In 1980 I discovered that CdTe layers could be deposited electrochemically in a simple beaker, as theorized by F.A. Kröger, without having to use much heavier vacuum processes.The electrochemical deposition of CdTe immediately became one of the major themes of my research, and remained so until the 2000s. The analysis of deposition mechanisms and their relationships to film properties were the subject of numerous publications and theses, with some outstanding results, in particular the synthesis of a new phase such as CdTe2, the study of as-grown semiconducting properties , the demonstration of epitaxial growth.This work gave rise to two major lines of research with far-reaching consequences. The first concerns the extension of electrochemical synthesis to other compound semiconductors of oxide type, with the discovery of the electrochemical synthesis of ZnO by cathodic reduction in the presence of oxygen, leading to materials of exceptional crystalline quality, suitable for epitaxial deposition. Depending on the experimental conditions, the forms obtained can range from nanocolumns to compact films. These results have opened a new avenue at international level. They led us to introduce them into the photovoltaic field for the formation of TCOs or hybrid matrices for dye cells. The second concerns the electrochemical synthesis of CuInGaSe2 (note CIGS), a ternary semiconductor of major industrial importance to photovoltaics. Initiated in the early 90s, this work involved both fundamental research and the creation of an industrial outlet. It led to the creation of a laboratory dedicated to photovoltaics with EDF in 2002, which succeeded in the creation of a start-up in 2009, NEXCIS, which achieved world-class performance in the field. This adventure has been the subject of a book chapter. Today, it continues with the creation of a new start-up, that I founded in 2021, that is using the electrodeposition technology to manufacture ultra-light, flexible, high-efficiency photovoltaic modules for new applications.This vision of the fundamental and underestimated interest of solution growth methods (electrochemistry or CBD) for the development of high-quality functional materials, particularly for photovoltaic conversion, has guided my entire scientific approach to date. The emergence of halogenated perovskite cells, also prepared in solution, has recently reinforced this approach as a way forward.Selected references:RECOMBINATION AND CHARGE-TRANSFER AT THE ILLUMINATED N-CdTe ELECTROLYTE INTERFACE - SIMPLIFIED KINETIC-MODEL ,LINCOT, D; VEDEL, J, JOURNAL OF ELECTROANALYTICAL CHEMISTRY 220 (1987) 179MECHANISM OF CHEMICAL BATH DEPOSITION OF CADMIUM-SULFIDE THIN-FILMS IN THE AMMONIA-THIOUREA SYSTEM - IN-SITU KINETIC-STUDY AND MODELIZATION, ORTEGABORGES, R; LINCOT, D, JOURNAL OF THE ELECTROCHEMICAL SOCIETY 140 (1993)3464.SOLAR-CELLS WITH IMPROVED EFFICIENCY BASED ON ELECTRODEPOSITED COPPER INDIUM DISELENIDE THIN-FILMS, GUILLEMOLES, JF; COWACHE, P; MASSACCESSI, S; THOUIN, L; SANCHEZ, S; LINCOT, D; VEDEL, J., Advanced Materials 6 (1994)379Mechanistic study of cathodic electrodeposition of zinc oxide and zinc hydroxychloride films from oxygenated aqueous zinc chloride solutions, Peulon, S; Lincot, D , JOURNAL OF THE ELECTROCHEMICAL SOCIETY 145 (1998)864Solution growth of functional zinc oxide films and nanostructures, Lincot, D., MRS BULLETIN 35(2010) 778From the Lab to Scaling-up Thin Film Solar Absorbers. Hariklia Deligianni, Lubomyr T. Roamnkiw, Daniel Lincot, Pierre-Philippe Grand. Book Chapter in Advances in Electrochemical Science and Engineering,XVIII (2018)

Enhancing efficiency of photoelectrochemical water splitting using zinc vanadate nanosheets (ZV) on manganese vanadate needle flowers (MV) supported by carbon nanofibers

Zinc and Manganese vanadates are highly regarded as potential photoanode materials for photoelectrochemical (PEC) water splitting due to their limited bandgap, varying optical and electrical characteristics based on their composition, and robust nature. To advance the practical use these materials, it is essential to creating precisely composed and structured Zinc and Manganese vanadates to enhance their overall effectiveness. In this work, we employed various morphologies, such as nanobelt flower like Zinc vanadate (ZV), nano-needle like Manganese vanadate (MV), a composite with ZV and MV, and a ZV-MV@CNF ternary composition. These novel morphologies grown on ITO substrate using a simple, hydrothermal approach without using any seed layer. The structural, surface, and optical examinations confirmed that the ZV-MV@CNF catalyst had superior visible light absorption, accelerated charge transfer, heterojunction interface between ZV and MV, and increased electron mobility, leading to outstanding photoelectrochemical performance. The photocurrent density of the ZV-MV@CNF photoanode reached 6.59 mA cm−2 at 1 V versus Ag/AgCl in a 0.25 M KOH solution under the illumination light. These results are ∼3.00, 3.52, and 1.28 times greater than the pristine ZV, MV, and ZV-MV, respectively. The fine-tuned ZV, MV, ZV-MV, and ZV-MV@CNF electrodes showed applied bias photon to current efficiency (ABPE) values of 0.09 %, 0.06 %, 0.14 %, and 0.18 %, respectively. The improved photoelectrochemical behavior of the ZV-MV@CNF electrode is credited to the excellent light absorption, and the remarkable catalytic and charge transport capabilities of CNFs. Therefore, these experimental results and characterization analysis suggested that advanced hierarchical nanostructures hold significant promise for water splitting applications.

Enhanced photoelectrochemical water splitting and photocatalytic decomposition performance of visible light active MgMnO3 perovskite nanostructure

Clean energy production and environmental remediation are imperative for sustainable future. Specially, exploration of multifunctional catalyst, for production of low-cost and eco-friendly hydrogen (H2) fuel as well as efficient decomposition of emerging pollutants are certainly needed. This study investigates magnesium manganese oxide (MgMnO3), a perovskite oxide, synthesized by simple citrate sol–gel technique, and its structural, morphological, optical, and photoelectrochemical properties were analyzed for the photodegradation of ciprofloxacin (CIP) antibiotic, methylene blue (MB) dye, and photoelectrochemical (PEC) water splitting. The cubic spinel crystal structure of MgMnO3 was confirmed through powder X-ray diffraction (XRD) analysis. FE-SEM images of the MgMnO3 material revealed a cauliflower-like morphology, consisting of an assembly of microspherical grains of varying sizes. UV–Vis spectroscopy exhibited broad absorption in the UV–Visible region, and the Tauc plot estimated a band gap of 1.54 eV. The MgMnO3 catalyst showed 88% and 96% for photodecomposition of CIP (10 mg/L) and MB (10 mg/L), respectively, using 35 mg and 30 mg of catalyst quantity over 90 min. In addition, MgMnO3 photoelectrode showcases superior photoelectrochemical behavior, exhibiting maximal photocurrent density of 13.21 mA cm−2 measured at 1.2 V vs. RHE and achieving a solar-to-hydrogen conversion efficiency of 2.45% compared to MgO and MnO2 photoelectrode. EIS measurements of MgMnO3 show enhanced charge transfer and recombination kinetics. Notably, the MgMnO3 electrode reveals outstanding photoelectrochemical durability, maintaining its stability even after continuous illumination for 9 h. Improved PEC properties could be attributed to wider light absorption, enhanced photo-induced charge-separations, and electron mobility. Thus, present study established an efficient and enduring multifunctional catalyst, catering photocatalytic degradation and PEC H2 generation.

Enhanced solar-driven photoelectrochemical water splitting of H/N co-doped TiO2: Role of defect states in a band gap reduction and promotion of charge transfer

Photoelectrodes based on reduced TiO2 are being extensively studied in the search for photocatalytic materials that can perform solar-driven water splitting and renewable hydrogen production. To date, substantial efforts have been devoted to understanding the microscopic mechanisms that underlie their photoelectrochemical (PEC) behavior, but this is a critical missing input to the Ti 3d carriers that govern the PEC activity. In this study the single and co-doping (N, H) in anatase TiO2 are prepared for PEC hydrogen production. The codoped photocathode delivers much better PEC performance from the enhanced solar light response and a fast electron pathway. Soft x-ray spectroscopy including x-ray absorption (XAS) and photoelectron spectroscopy (XPS) has been used to investigate the location and occupation of the defect levels from doping, through which the relevant engineered electronic properties in doped TiO2 are determined. It is shown that co-doping effectively produce the substitutional nitrogen in comparison with single doping. The Ti3+ defect states promoted by doping introduces localized Ti 3d-derived states below Fermi level (EF), resulting in a large reduction (approximately 1 eV) in the band gap of co-doped TiO2. The progressive production of oxygen vacancies eventually causes a surface band upward-bending induced electron transfer mechanism critical for charge separation. The present insights into defect chemistry and its determination to the electronic structure of co-doped TiO2 provide important guidance for using TiO2 in electrocatalysis and optoelectronics.

A Visible Light-Responsive TiO2 Photocathode Achieved by a Rh Dopant.

Developing an efficient and stable photocathode material for photoelectrochemical solar water splitting remains challenging. Herein, we demonstrate the potential of rutile TiO2 as a photocathode by Rh doping with visible light absorption up to 640 nm and an onset potential of 0.9 V versus the reversible hydrogen electrode. The dopant transforms the rutile host from an n-type semiconductor to a p-type one, as confirmed by the Mott-Schottky curve and kelvin probe force microscopy. Physical and photoelectrochemical analyses further suggest that the doping mechanism is dependent on concentration. Lower levels of dopants generate localized Rh3+, while higher levels favor Rh4+ that interacts more strongly with the O 2p orbitals. The latter is found not only to extend the visible light absorption range but also to facilitate charge transport. This work elucidates the role of the Rh dopant in adjusting the photoelectrochemical behavior of TiO2, and it provides a promising photocathode material for solar energy conversion.

Unveiling the critical role of crystallinity in photogenerated hole transfer behavior of TiO2 with an aminoxyl radical mediator

Integrating aminoxyl radical mediators (ARMs) with titanium dioxide (TiO2) based photoelectrochemical (PEC) processes presents a promising approach for achieving mild and sustainable chemical transformations. However, a comprehensive understanding of the interaction between ARMs and PEC processes remains elusive. This study investigates the PEC behavior of photoelectrodes fabricated from single- and polycrystalline TiO2 in the presence of a representative ARM, 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl radical, in acetonitrile. Interestingly, we observe contrasting PEC behavior: photocurrent enhancement for single-crystalline TiO2 and photocurrent suppression for polycrystalline TiO2. We attribute this difference to subtle variations in surface properties arising from the material’s crystallinity. Photoelectrochemical impedance spectroscopy (PEIS) is employed to gain deeper insights into the influence of surface defects on charge transfer and recombination mechanisms. The PEIS results suggest that an anomalous hole transfer mechanism mediated by surface trap states governs the PEC performance of polycrystalline TiO2.

Dual Functionality of Surface States in Dictating Photocurrent Generation of Au Nanocluster-Sensitized TiO2 Electrodes.

Gold nanoclusters (Au NCs), composed of only a few atoms, exhibit molecule-like behavior due to their distinct electronic structures arising from quantum confinement effects. Unlike their plasmonic nanoparticle counterparts, these nonplasmonic Au NCs possess unique properties with significant potential for photosensitizer applications. While traditional and NC-based electrodes share architectural similarities, the photoelectrochemical (PEC) behavior of the latter diverges significantly. Sensitizing TiO2 with Au NCs introduces additional surface trap states. In contrast to conventional photosensitizers, where surface states typically have a negligible impact on hole transfer, these trap states actively mediate the charge transfer process in Au NC-sensitized TiO2 electrodes. In this study, we employed impedance spectroscopy to elucidate the role of surface trap states in photocurrent generation. Our investigation revealed that these states are critical in determining PEC performance, presenting a dichotomy: they facilitate charge transfer (enhancing PEC performance) while simultaneously promoting carrier recombination (limiting efficiency). We demonstrated that the judicious control of otherwise deleterious surface trap states can significantly boost photocurrent. Our findings highlight that the dual nature of surface trap states demands a comprehensive investigation to fully understand their intricate impact on PEC performance.

Effect of annealing temperature on physical properties and photoelectrochemical behavior of electrodeposited nanostructured NiO thin films for optoelectronic applications

Our paper used a low-cost electrodeposition technique to grow Nickel Oxide (NiO) thin films on fluorine-doped tin oxide (FTO) substrate. As-deposited films were annealed at different temperatures (350, 400, 450, and 500 °C). X-ray diffraction (XRD), Raman spectroscopy (RAM), scanning electron microscopy (SEM), UV–vis spectrophotometer, photoluminescence (PL), Cyclic voltammetry (CV), photocurrent (PC), electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis (MS) were used to study and investigate the effect of annealing temperatures on the structural, morphological, electrical, and optical properties of prepared thin films. XRD patterns proved the cubic phase of all NiO samples with the preferential orientation in (111) direction. SEM results showed that the grain size increased with increasing annealing temperature. The optical transmission was studied by a UV–vis spectrophotometer, where high transmittance for NiO thin films was found to vary in the range of 73–84 % in the visible wavelength region, depending on the annealing temperatures. At the same time, UV–visible measurements indicate an absorption band edge at 311 nm, mainly recognized as a characteristic direct band gap for prepared NiO. The optical gap calculated from the Tauc relation showed a decreasing trend from 3.97 to 3.86 eV with increasing annealing temperature from 300 °C to 500 °C. PL spectra of synthesized samples revealed two distinct emission peaks at around 400 nm and 490 nm. RAM analysis confirmed the presence of three characteristic peaks related to the vibration of Ni–O bonds. The NiO film annealed at 500 °C displays the highest specific capacitance value by CV analysis. The P-type conductivity of manufactured arrays and enhanced electrical properties were confirmed by PC, EIS, and MS analysis. The highest carrier concentration values (9.19 × 1018 cm−3) and flat band potential (0.82 V) were obtained for samples annealed at 500 °C. Our outcomes proved that NiO-500 °C thin films are ideal candidates for optoelectronic applications.

New insights into the photoassisted anodic reactions of n-type 4H SiC semiconductors

This study aims to investigate the photoelectrochemical behavior of the n-type 4H-SiC, focusing on aqueous, hydroxide-based electrolytes. Despite its high stability, this wide-bandgap semiconductor material undergoes electrochemical reactions, such as anodic oxidation or etching, under specific conditions. Since electrons are the majority charge carriers in n-type semiconductors, oxidation processes require above-bandgap illumination. Then, the reaction rate is influenced by the number of electron holes available for an oxidation process and the velocity of the transport of hydroxide ions to/from the surface. The goal is to focus on the essential reaction parameters (i.e., potential and electrolyte concentration) to clarify the reaction mechanism in aqueous (alkaline) electrolytes. Methods with controllable hydrodynamic conditions are required to investigate the transport processes in the electrolyte. Even though the rotating disk electrode (RDE) is a commonly used and powerful method, it is not well suited for our purpose. Photoelectrochemical etching of SiC is extraordinary because it involves both mass transfer phenomena and gas evolution but also needs high-intensity illumination from an appropriate light source. Hence, a new concept for an inverted rotating cell was developed and implemented. This setup was used to study the effect of the mass transport of hydroxide ions on the photoelectrochemical behavior of SiC in each potential region at varying rotation speeds. In order to interpret the experimental findings, a distinct electrical network model was formulated for simulating the results, aiding in unraveling the underlying reaction mechanism. Electrochemical measurements were complemented by surface-sensitive analytical techniques. XPS was the method of choice to investigate the composition of the sample surface before and after etching. SEM and AFM allow the characterization of the surface morphology in the initial stages of etching. The totality of this information provides a complete picture of the complex processes in the vicinity of the semiconductor electrode.Graphical abstract

Selective additions of dopants, Co-catalyst and surfactant on the hydrothermally synthesized BiVO4 semiconductors for outstanding photoelectrochemical water oxidation behavior

The present study describes the significant improvement of the PEC performance through modifications via co-doping of Mo/W and optimizing the level of surfactant (Triton-X 100; TX-100) addition to the hydrothermally synthesized BiVO4 photoanode. The photoelectrochemical performance is improved when the precursor solution contains an optimized 5 % TX-100 surfactant level. The visible light responsiveness of the semiconductor photocatalyst has been confirmed using linear sweep voltammograms under periodic chopped illumination of UV–vis and visible irradiation for H2O → O2 oxidation. Adding an optimized level of Mo and W to the precursor solution leads to modifications of the crystallites, which facilitates the water oxidation reaction and exhibits the highest photo-current of ∼0.61 mA cm−2. Selective loading of oxygen evolution catalyst (OEC) in the surface boosts the PEC performance to 1.05 mA cm−2 and significantly increases photon current conversion efficiency.

Nickel porphyrin/ZnIn2S4 heterojunction with Ni-S highway for boosting charge separation and visible-light-driven H2 production

Due to the exceptional potential to retard the charge recombination, semiconductor-based heterojunctions as photocatalysts have attracted extensive attention. Herein, nickel(II) 5,10,15,20-tetraphenyl-21H,23H-porphyrin (NiTPP) and ZnIn2S4 (ZIS) floriated microspheres are used to construct a novel inorganic-organic heterojunction (NiTPP/ZIS). Compared with the NiTPP and ZIS, the resultant NiTPP/ZIS exhibits enhanced optical absorption, charge separation and photoelectrochemical behavior. Further investigations demonstrate that a type II heterojunction mechanism proceeds in the NiTPP/ZIS heterojunction to boost the charge separation via the Ni-S highway formed between the NiTPP and ZIS components. No need of additional cocatalyst, the NiTPP/ZIS heterojunction with an optimal mass ratio delivers a superior apparent quantum yield of 64.0% at 400 nm and a remarkable H2 evolution activity of 2305 μmol h−1 under visible light (λ ≥ 400 nm) irradiation, 10 and 256 times higher than that of the ZIS and NiTPP alone, respectively. This work presents a new concept for constructing inorganic-organic heterojunctions for high-performance artificial photosynthesis systems.

Synthesis of lead-free Cu/CuFeO2/CZTS thin film as a novel photocatalytic hydrogen generator from wastewater and solar cell applications

The sewage water is tested as a source of hydrogen production with a high efficiency value of 25.44% using Cu/CuFeO2 (delafossite)/CZTS (Cu2ZnSnS4, kesterite) as an investigated photocatalyst. The X-ray diffraction (XRD) analysis of the investigated photocatalyst (Cu/CuFeO2/CZTS) revealed a compact crystalline material, as witnessed by the diffraction peaks with high intensities. From the optical characterization, the recorded band gap values of Cu/CuFeO2/CZTS, Cu/CuFeO2, and CZTS are 1.15, 1.97, and 1.43 eV, respectively, inferring an obvious enhancement in the optical properties of the investigated photocatalyst, Cu/CuFeO2/CZTS. The photoelectrochemical (PEC) performance of the investigated photocatalyst for hydrogen (H2) generation was examined in wastewater. The current–time characteristic and the PEC behavior of Cu/CuFeO2/CZTS in dark and under light illumination using various power densities, monochromatic wavelengths, and different temperatures were studied. The current densities (JPh) under light illumination and (Jo) in the dark were − 8.0 and − 0.7 mA cm−2, respectively. The H2 generation rate for the Cu/CuFeO2/CZTS electrode was 0.049 mA/h. The thermodynamic parameters, respectively, ΔS*, ΔE, and ΔH* were 28.76 kJ mol−1 K−1, 21.0, and 18.28 kJ mol−1 at 390 nm. The findings of the work hold great promise for addressing energy production and the hindrances of sewage treatment at the same time.

Exploring the photoelectrochemical process through surface states of plasmonic Ag-loaded NiFe-LDH-modified CuWO4 photoanode

Optimizing the interfacial action of photoanode for photoelectrochemical (PEC) behavior to facilitate charge transport is essential for enhancing solar-to-fuel efficiency. Herein, a typical CuWO4/NiFe-LDH/Ag photoanode was reported and an alternative pathway for charge transfer in the PEC process through surface states mechanism was elucidated. In particular, the layer double hydroxides (NiFe-LDH) acted as charge-transfer agents to facilitate the transfer of photogenerated carriers; while the surface plasmon resonance (SPR) effect of the Ag provided hot electrons, which increased the carrier concentration and promoted the charge separation. The influence of presence of surface states on the PEC process was systematically illustrated. Experimental results indicated that the optimized CuWO4/NiFe-LDH/Ag photoanode displayed a photocurrent that was more than an order of magnitude larger than that of the pure CuWO4 (increasing from 0.30 mA cm−2 to 1.45 mA cm−2 at 1.23 V vs. RHE), accompanied by favorable electrochemical impedance and stability (maintaining 92.4%). Importantly, increasing the available filled surface states could be beneficial in enhancing the PEC behavior. This work provided additional insights into photoanode charge transport in PEC processes.

Electrolyte Effect on Photoetching of Gallium Nitride

The limited material removal rate of conventional chemical mechanical polishing (CMP) significantly hinders the fabrication efficiency and surface quality, thereby preventing the development of gallium nitride (GaN)-based devices. Moreover, the incorporation of photoelectrochemistry in CMP has garnered increasing attention because of its potential to enhance the quality and efficiency of the GaN process. However, a considerable gap still exists in the comprehensive understanding of the specific photoelectrochemical (PEC) behavior of GaN. Here, we report the influence of the electrolyte on the PEC etching of GaN. Various acids and bases were tested, with their pH being carefully adjusted. The concentrations of the cations and anions were also examined. The results showed that photocorrosion/photoetching was more pronounced in sulfuric acid, phosphoric acid, and nitric acid environments than in alkaline environments, but it was less pronounced in hydrochloric acid. Furthermore, the effects of pH and anion concentration on photoetching were investigated, and the results revealed that photoetching in acidic environments weakened with increasing pH levels and diminished with increasing sulfate concentration. The underlying reasons contributing to this observation were explored. These findings provide ideas for improving the photoetching efficiency of GaN, thereby enriching the photoelectrochemical mechanical polishing (PECMP) technology of GaN.

Enhancing the solar hydrogen generation performance of nickel-oxide nanostructured thin films doped with molybdenum

Using technology to store solar energy as hydrogen fuel (H2) on a scale corresponding to global energy use is a viable way to alleviate the energy crisis and environmental deterioration. This research deals with the manufacture of thin films prepared from nickel oxide (NiO) and their use in the photoelectrochemical (PEC) water-splitting process to produce green H2 as a clean energy fuel. Herein, pure and Mo-doped NiO thin films were successfully prepared using a straightforward sputtering method at different radio frequency (RF) power for the Mo target from 0 to 50 watt. x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDX), and UV–vis spectroscopy techniques were used to analyze the structural, morphological, chemical composition, and optical characterization of the prepared films. The PEC behaviours for green H2 production and the impedance spectroscopy measurements were also investigated for all samples. In PEC measurements, the 50 W sample showed the highest PEC performance. At −0.4V versus RHE, the 50 W sample verified the highest value for the photocurrent density of about 1.7 mA cm−2 which was approximately four times more than the pure NiO sample. The applied biased photon-to-current conversion efficiency and incident photon-to-current conversion efficiency were also estimated. This research provided a fresh viewpoint on the design of highly active NiO-based photo-catalysts for the production of green H2 powered by solar light.

Deciphering the photoelectrochemical behaviour of MoSe2-decorated BiVO4 as a dual system for concurrent degradation of methylene blue and hydrogen generation

Green hydrogen production through photoelectrochemical (PEC) water splitting offers a sustainable energy solution, but the utilization of low-quality water is essential to conserve freshwater resources. Repurposing industrial wastewater, a substantial global issue, for PEC water splitting remains underexplored due to challenges in photoelectrode efficiency and stability. In this study, we present a MoSe2-decorated BiVO4 heterostructured photoelectrode (MoSe2/BiVO4 or BM) for green hydrogen production and efficient wastewater treatment. The optimized system yields a hydrogen production rate of 0.113 mmol from synthetic textile water (utilizing methylene blue as a model pollutant) while achieving a 94.74% degradation of pollutants. Synthesized via a hydrothermal route, BM demonstrates a high photocurrent density of 2.57 mA/cm2 at 1.23 V vs RHE, surpassing BV alone (0.14 mA/cm2). Further, BM shows incident photon to current efficiency (IPCE) of 12.24% and applied bias to photocurrent efficiency (ABPE) of 0.59%. Scavenger studies elucidate the role of holes in MB degradation. Tested in textile wastewater treatment outlets, BM exhibits a hydrogen production rate of 6.155 μmoles alongside reduced COD, BOD, TOC, and microbial load, showcasing its dual capability for hydrogen generation and simultaneous wastewater treatment. Thus, the efficiently designed type-II heterostructure formed between BV and MS behaves as a dual system with demonstrated usage in low-quality water for hydrogen generation with its simultaneous treatment.

Structural, optical and photoelectrochemical behavior of facile electrodeposition of organic/inorganic hybrid film

Structural, optical and photoelectrochemical behavior of facile electrodeposition of organic/inorganic hybrid film

Time Constant Estimation and Alleviation of Interior Charge Recombination for Photocatalytic Reaction Guided by Correlation with Photoelectrochemical Behaviors.

Interior charge recombination that inherently competes with the separation of photogenerated charges is crucial to the photocatalytic utilization of incident photons. We here propose to simultaneously promote both the desired hole extraction and semiconductor-cocatalyst interfacial electron transfer and suppress the undesired interior charge recombination by shifting the equilibrium potential of the semiconductor in an actual photocatalytic reaction. By correlating with these interfacial electronic processes, we estimate the time constants for the occurrence of interior charge recombination, which range from several milliseconds to several deciseconds in the actual photocatalytic reaction. This time scale estimated from photoelectrochemical behaviors not only provides a substantial guide to photocatalytic reaction design but also avoids relying on a very dense photon beam that greatly deviates from actual working conditions to generate discernible optical signals in certain common methods.

Effect of the Heterovalent Sc3+ and Nb5+ Doping on Photoelectrochemical Behavior of Anatase TiO2

In this study, we explored the effect of either Nb or Sc doping at a concentration range of 0.0–1.0 at.% on the physical–chemical and photoelectrochemical behavior of TiO2 anatase electrodes. This behavior was characterized by work function, flat band potential, donor density, spectral dependence of photocurrent and stationary photocurrent measurements. All experimental results are interpreted in terms of the formation of the shallow delocalized polaron states in the case of Nb doping and deep acceptor states induced by Sc doping on TiO2 anatase.