Successive Ionic Layer Adsorption Reaction Research Articles

Z-scheme BiOBr/WS2 heterojunction with integrated photocatalytic degradation and photothermal water evaporation for effective dye wastewater purification

The restoration of water resources and the optimization of solar energy use are critical challenges. In this study, hydrophilic BiOBr/WS2 Z-scheme heterojunctions were prepared using a series of reactions for solar interface water evaporation and photocatalytic degradation of RhB. WS2 nanoparticles were deposited on the surface of titanium mesh using a hydrothermal method, and BiOBr nanosheets were further modified on WS2 using a successive ionic layer adsorption reaction (SILAR) method and solvothermal method. The relatively broad absorption range of WS2 in the full spectrum resulted in enhanced light absorption and improved light utilization of BiOBr/WS2. The formation of Z-scheme heterojunction between BiOBr and WS2 improved the hydrophilicity of the material, enhanced the photocatalytic degradation of organic pollutants in BiOBr/WS2 composite materials, and improved the solar interface water evaporation performance. The degradation rate of RhB by BiOBr/WS2 could reach 95.6% under one solar irradiation, and the photothermal water evaporation rate could reach 1.81 kgꞏm-2ꞏh-1. This study solved the problem of dye enrichment on solar absorber and provided a new way to construct an efficient solar interfacial water evaporation-photocatalytic system to treat dye wastewater.

Fabrication and Characterization of Aluminum-Doped Nickel Oxide Thin Films for Optoelectronic Applications using the SILAR Method

Study’s Excerpt The effect of varying annealing times on 10% Aluminum-doped Nickel Oxide (ANO) thin films, deposited via the SILAR technique is presented. SEM and RBS analyses were used for detailed correlation between annealing time and the film's microstructural improvements. ANO thin films could be used for advanced technological applications. Full Abstract The effect of varying the annealing time of %10 aluminium-doped Nickel Oxide thin film was studied to understand the possible effect on the optical, structural, and electrical properties of %10 aluminium-doped Nickel Oxide (ANO) for possible application. The thin films were deposited on glass substrates using the successive ionic layer adsorption reaction (SILAR) deposition technique. The samples formed were annealed at 3000C, and the annealing time varied at 1.35 hrs., 1.45 hrs., 1.55 hrs., and 2 hrs, respectively. The deposited films were characterized to obtain the optical, electrical, and structural characteristics and the compositional constituent of the film using the double beam photo spectrometer, Four-Point Probe, Scanned electron Microscope, Energy Dispersion Spectroscopy, and X-ray Diffractometer. The films were observed to have low absorbance in the range of 0.1 to 0.01 and high % transmittance within the range of 80% - 98% in the visible region of the spectrum. The reflectance of the film was observed to decrease with an increase in annealing time in the range of 10% - 2.5%, all in the visible region of the spectrum. The crystallite size of the deposited films decreased with increased annealing time with the structural formation of simple cubic phase NiO thin film. SEM micrograph of the thin films reveals that an increase in annealing time improved the crystallinity of the films with the grain size evenly distributed. The EDS result of the deposited films revealed the presence of nickel, aluminum and Oxygen as the major constituent of the deposited films. The Ruther Ford Backscattering (RBS) analysis of the thickness of the films shows an increase in the thickness with an increase in annealing time. Clearer compositions of the films were also seen from the RBS analysis. Their electrical properties revealed that the films formed had low electrical resistivity and high conductivity, so they could be useful in making optoelectronics devices and corrosion resistance.

Improving photoelectrochemical performance of transferred TiO2 nanotubes onto FTO substrate with Mo2C and NiS as Co-catalyst

The photoelectrochemical (PEC) performance of titanium dioxide nanotube (TiO2 NT) photoelectrodes for sustainable hydrogen production has garnered significant research interest. Despite the advantages of TiO2 NT fabricated via anodization of titanium metal, such as their well-ordered vertical structure, challenges persist including the thick oxide barrier layer, limited optical transparancy, and the wide energy band gap (∼3.0 eV), which constrain their practical efficiency in PEC applications. This study addresses these limitations by introducing a novel approch to transfer TiO2 NT onto a fluorine-doped tin oxide (FTO) substrate. TiO2 NTs were synthesized with varying anodization times and steps to achieve optimal free-standing structures. To further enhance PEC performance, co-catalyst including molybdenum carbide (Mo2C) and nickel sulfide (NiS) were incorporated using immersion and successive ionic layer adsorption reaction (SILAR) methods, respectively. Comprehensive characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) provided insights into the crystal phase, morphological structure, band gap, and elemental composition of the photoelectrodes. Photoelectrochemical and photostability evaluations were conducted through linear scan voltammetry (LSV) and chronoamperometry under dark and light conditions. Results indicate that transferring TiO2 NTs onto FTO significantly enhanced photocurrent density, achieving a 2.5-fold increase at 0.7 V versus a TiO2 NT/Ti substrate. The incorporating of co-catalysts Mo2C, NiS and the combined NiS/Mo2C further enhanced the photocurrent density to 2.20, 3.00 and 8.00 mA cm−2 respectively, with a remarkable 31-fold enhancement compared to the TiO2 NT/Ti substrate. This findings underscore the potential of the TiO₂ NT/FTO photoelectrode with optimized co-catalyst integration for advanced photoelectrochemical applications.

Structural, morphological, and optical properties of CuO nanoblade-decorated TiO2 nanotubular photoelectrodes

Titania (TiO2) nanotubular photoelectrodes are a competitive component of titania-based photoelectrochemical water splitting systems. However, TiO2 actively absorbs light in the UV region, which limits its usefulness in solar water splitting, a fast-growing clean energy alternative. In this study, the structural, morphological and optical properties of CuO/TiO2 nanostructures on conductive transparent F-doped SnO2 (FTO) coated glass substrates are engineered for potential application in solar water splitting. The efficacy of a three-step anodization synthesis process to develop free-standing high-fidelity nanotubular TiO2 thin films (∼8μm) is demonstrated. CuO nanoblades were deposited on TiO2/FTO by a successive ionic layer adsorption reaction (SILAR). An increase in the precursor concentration and number of immersion cycles influenced the adsorption of CuO and the resultant red shift in the absorption range. SEM and TEM analyses confirm the formation of a heterostructure, with evidence of CuO nanostructures within the TiO2 nanotubular arrays and on the top of the tubes.

Deposition of CdSe Nanocrystals in Highly Porous SiO2 Matrices-In Situ Growth vs. Infiltration Methods.

Embedding quantum dots into porous matrices is a very beneficial approach for generating hybrid nanostructures with unique properties. In this contribution we explore strategies to dope nanoporous SiO2 thin films made by atomic layer deposition and selective wet chemical etching with precise control over pore size with CdSe quantum dots. Two distinct strategies were employed for quantum dot deposition: in situ growth of CdSe nanocrystals within the porous matrix via successive ionic layer adsorption reaction, and infiltration of pre-synthesized quantum dots. To address the impact of pore size, layers with 10 nm and 30 nm maximum pore diameter were used as the matrix. Our results show that though small pores are potentially accessible for the in situ approach, this strategy lacks controllability over the nanocrystal quality and size distribution. To dope layers with high-quality quantum dots with well-defined size distribution and optical properties, infiltration of preformed quantum dots is much more promising. It was observed that due to higher pore volume, 30 nm porous silica shows higher loading after treatment than the 10 nm porous silica matrix. This can be related to a better accessibility of the pores with higher pore size. The amount of infiltrated quantum dots can be influenced via drop-casting of additional solvents on a pre-drop-casted porous matrix as well as via varying the soaking time of a porous matrix in a quantum dot solution. Luminescent quantum dots deposited via this strategy keep their luminescent properties, and the resulting thin films with immobilized quantum dots are suited for integration into optoelectronic devices.

Facile preparation of CoFe-MnO2@titania nanotube array bifunctional electrodes for high-current-density water splitting at industrial temperatures

The development of bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at high current density under industrial temperatures is crucial for large-scale industrial hydrogen production from water splitting. In this work, M-MnO2@TNTA composite electrodes were prepared by depositing various metal ion-doped manganese oxide nanoparticles on the titania nanotube array (TNTA) by successive ionic layer adsorption reaction (SILAR) method, and their HER and OER electrocatalytic performances were investigated in 1 M KOH. Results show that the CoFe-MnO2@TNTA composite electrode prepared by simultaneous doping of Co3+ and Fe3+ in MnO2 exhibits optimal catalytic performance. Compared with MnO2@TNTA without ion doping, the overpotentials of CoFe-MnO2@TNTA at 10 mA cm−2 (η10) for HER and OER are reduced by 571 and 665 mV. In addition, the electrode performance can be significantly enhanced by increasing the test temperature, and the porous array structure enables CoFe-MnO2@TNTA to exhibit better performance at high current densities. At 50 °C, which is the common industrial electrolytic water temperature, the η10 of CoFe-MnO2@TNTA for HER is almost equal to that of the Pt/C electrode. The η100 of CoFe-MnO2@TNTA for HER is reduced by 35 mV compared with the Pt/C electrode. Moreover, η200 of CoFe-MnO2@TNTA for OER is significantly lowered by 111 and 184 mV compared with IrO2 and RuO2 electrodes. Utilizing CoFe-MnO2@TNTA as both the cathode and anode for overall water splitting, the electrolysis voltage is merely 2.33 V under the current density of 200 mA cm−2, much lower than that of IrO2 (+)||Pt/C (–) (2.68 V). The present work may provide a valuable reference for the development of self-supporting bifunctional electrodes suitable for high-current-density water splitting at industrial temperatures.

Synthesis and characterization of copper tin sulfide counter electrode for enhanced performance in third-generation solar cells

This paper presents the fabrication of a copper tin sulfide (CTS) counter electrode for application in third-generation solar cells. The fabrication process involved modified chemical bath deposition (M-CBD) or a successive ionic layer adsorption reaction (SILAR). Initially, a ZnO seed layer was deposited onto a fluorine-doped tin oxide (FTO) substrate via CBD. Subsequently, a mesoporous layer of ZnO was deposited onto the FTO substrate using the doctor-blade method. The mesoporous ZnO layer was sensitized with CdS nanocrystals deposited using the SILAR method. Various characterization techniques, including UV–Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), were employed to analyze the optical, structural, and morphological properties of the photoanode and CTS counter electrode. The results demonstrate the successful synthesis of a CTS counter electrode with desirable properties for solar-cell applications. The fabricated CTS counter electrode exhibited a conversion efficiency of 0.49%, which was significantly higher than that of carbon-based counter electrodes.

An ultra-sensitive photoelectrochemical biosensing platform based on the AgVO3/BiOI heterojunction for an enzyme activity inhibition reaction.

An ultra-sensitive photoelectrochemical sensing platform for profenofos detection based on the inhibition of catalase activity was prepared in this work. First, the novel functional nanocomposite material AgVO3/BiOI was prepared by a hot solvent method and successive ion layer adsorption reaction. Then, chitosan was employed as a dispersion medium to disperse and immobilize the catalase. Under visible light irradiation, the prepared CAT/CS/AgVO3/BiOI/ITO nanocomposite electrode generates a stable low photocurrent in hydrogen peroxide solution. When this electrode is immersed in a phosphate buffer solution containing profenofos, the activity of the catalase is inhibited, resulting in an increase in the photocurrent. Under the optimized experimental conditions, the profenofos concentration and increase in photocurrent are linearly related in the concentration range of 1 × 10-10 to 5.0 × 10-8 mol L-1, and the limit of detection is 1.0 × 10-11 mol L-1. This biosensor shows good selectivity for detecting profenofos in fruits and vegetables, and the determination results of profenofos are satisfactory.

Electroactive Prussian Blue Analogues/TiO2 Nanocomposites Obtained through SILAR Assembly in Mesoporous Nanoarchitectures

AbstractThe preparation of nanomaterials for energy applications such as intercalation batteries and materials that can act as substrates for water oxidation is a subject of major interest nowadays. In this work, we report the deposition of Prussian blue (PB) and its cobalt analogue (CoPBA) on mesoporous titania thin films (MTTF) using the successive ionic layer adsorption reaction (SILAR) technique under soft conditions. A bifunctional ligand, 1,10‐phenanthroline‐5,6‐dione (pd), was used to functionalize the titania surface and promote the growth of PB and CoPBA. The resulting PB@MTTF and CoPBA@MTTF nanocomposites were characterized using several techniques and it was determined that PB and CoPBA grow in a controlled and sequential manner, maintaining the mesoporous architecture. Both PB@MTTF and CoPBA@MTTF demonstrated very good electroactive properties, while CoPBA@MTTF exhibited water oxidation capabilities. The flexibility of this PBA@MTTF platform allows the incorporation of any labile transition metal ion or fragment into the structure of the coordination polymer embedded into a mesoporous matrix, opening the door for (photo)electrochemical devices and catalysts.

Hierarchically crystalline copper borate nanosheets as a freestanding electrode for a hybrid supercapacitor

In this study, we have suggested a straightforward approach to fabricating a binder-free electrode of hierarchically crystalline copper borate (Cu-Bi) nanosheets grown on nickel foam using the Successive Ionic Layer Adsorption Reaction (SILAR) method. The best-performing electrode shows a remarkable specific capacitance (Cs) of 2002 Fg−1 at 1 Ag−1 and Cs retention of 85 % for 10,000 GCD cycles. The assembled CB/NF-2//AC device exhibits high cycling stability and achieves a high energy of 52.2 Whkg−1 at a power density of 2622.4 Wkg−1. Remarkably, it reached 152.7 Fg−1 at 2 Ag−1, and the device still has a high capacitance retention of 85 % for 10,000 cycles. This remarkable electrochemical activity could be attributed to: (i) the inherent defects of the prepared electrode via the existence of borates, providing straightforward interaction between the electrolyte and the active species; (ii) designing the hierarchical architecture that could provide a porous nanosheet structure, which generates accessible active sites for quick ion transport, boosting the Cs; (iii) the formation of crystalline Cu-Bi nanosheets, resulting in high stability and superior electrochemical performance compared to the previous amorphous borides; and (iv) the hybridization between the B 2p state and the multiple d-orbitals of transition metals, increasing the electron flow between the atoms. The current work suggests that the growth of hierarchically crystalline Cu-Bi on Ni foam using a low-cost and simple procedure could provide a practical approach to designing hybrid supercapacitors with outstanding electrochemical performance.

Constructing a CdS QDs/silica gel composite with high photosensitivity and prolonged recyclable operability for enhanced visible-light-driven NADH regeneration

Visible-light-driven nicotinamide adenine dinucleotide (NADH) regeneration is one of the most effective measures, and cadmium sulfide (CdS) materials are typically used as low-cost photocatalysts. The CdS photocatalysts, however, still suffer from low regeneration efficiency and poor cycle stability. In this work, the CdS quantum dots (QDs) less than 10 nm embedded onto silica gel (CdS QDs/Silica gel) were constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. Results demonstrate that the photosensitivity of the CdS QDs/Silica gel composite was 31 times higher than that of the bulk CdS. Moreover, the conduction band (CB) edge of the CdS QDs/Silica gel composite is −1.34 eV, which is more negative 0.5 eV than that of the bulk CdS. The obtained CdS QDs/Silica gel composites showed the highest NADH regeneration yields of 68.8% under visible-light (LED, 420 nm) illumination and can be reused for over 40 cycles. Finally, the bioactivity of NADH toward enzyme catalysis is further confirmed by the hydrogenation of benzaldehyde to benzyl alcohol catalyzed with an alcohol dehydrogenase as enzyme catalysis.

Investigation of the Optical Properties and Bandgap Energy of CdCuS Using the Successive Ionic Layer Adsorption Reaction (SILAR) Method of Thin Film Deposition

Investigation of the Optical Properties and Bandgap Energy of CdCuS Using the Successive Ionic Layer Adsorption Reaction (SILAR) Method of Thin Film Deposition

Recent Advancements in the Synthetic Mechanism and Surface Engineering of Transition Metal Selenides for Energy Storage and Conversion Applications

Novel catalytic materials are under investigation to find convincing energy alternatives. In this context, transition metal selenides (TMSes) are found to be feasible, ecofriendly, and effective electrocatalysts with futuristic characteristics. A deep and comprehensive investigation on metal selenides for energy conversion and storage application is summarized in this review article. Different methods such as hydrothermal, solvothermal, coprecipitation, hot injection, successive ionic layer adsorption reaction, polyol, and others can be used for the synthesis of metal selenides based electrocatalysts, with different morphologies and compositions. The morphology of metal selenides is strongly controlled by factors such as reaction time, temperature, pH of the reaction medium, and surfactant. The electrochemical applications of metal selenides are governed by morphology, active spots for reaction, surface engineering, and confinement. It is concluded that TMSes deliver high performance with large surface area, which is possible due to their porous or 3D morphology. The TMSes with multimetal or with doping metal/nonmetals perform better compared to single atoms. It is concluded that the reaction mechanism of hydrogen evolution reaction and oxygen evolution reaction is a primary tool to better understand the system to develop more efficient catalysts for practical application.

Performance of CdS/TNTAs Nanocomposite in Removing Ciprofloxacin and Hydrogen Production using Simultaneously Electrocoagulation-Photocatalysis Process

This study used CdS as a pair of TiO2 Nanotube Arrays (TNTAs), considering the position and width of the energy band gap, which is expected to increase photocatalyst performance. The nancomposite was synthesized using the successive ionic layer adsorption reaction (SILAR) method, with Cd(CH3COO)2 and Na2S as precursors. The CdS/TNTAs nanocomposite is expected to reduce the energy band gap to enable the visible and UV spectrum to activate the photocatalyst. Additionally, the formed heterojunction mechanism provides opportunities for the trajectories of electrons and holes to be farther apart and reduce the recombination rate. The degradation ability of CdS/TNTAs nanocomposite in the photocatalytic process was evaluated using samples of ciprofloxacin liquid waste as an antibiotic, which is quite challenging to decompose completely. The ability of the photocatalytic process to produce hydrogen gas was also observed and its performance synergized with the electrocoagulation process. The result showed that the use of CdS as a TNTAs partner in CdS/TNTAs nanocomposites affects increasing photocatalyst performance, both in degrading ciprofloxacin and producing hydrogen gas. Furthermore, the CdS/TNTAs nanocomposite increased the photocatalytic process’s ability to degrade ciprofloxacin and produce hydrogen from 8.5 to 20.5% and 6 to 23.5 mmol/m2 compared to using TNTAs alone. The processing capability is further enhanced when run in synergy with the electrocoagulation process where the removal of ciprofloxacin reaches 86.55% and the hydrogen produced is 2.62×106 mmol/m2. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Construction of BiOCl-TNTs photoelectrochemical sensor for detection of hydrogen peroxide

In this study, BiOCl-TNTs photoelectrochemical sensors were fabricated by a combining technique of successive ionic layer adsorption reaction (SILAR) and anodic oxidation. The characterization techniques and electrochemical tests show that the as-prepared BiOCl-TNTs photoelectrochemical sensor possesses good photoelectric properties. And it has a fast photoelectric response to H2O2. The range of detection of H2O2 is 1 × 10−7 nM to 10 mM, the sensitivity is 14.69 μA mM−1 cm−2 and the lower detection limit is 0.05 nM (S/N = 3), and it exhibits good stability and selectivity. The results indicated that the BiOCl sensitization improved photocurrent response, and enhanced photoelectrocatalytic activity induced by solar energy.

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Development of novel TiN–LiAlSiO4/SnS/AuPd multilayer films for H2 generation by photocatalysis

TiN–LiAlSiO4/SnS/AuPd multilayer films were deposited on glass substrates using screen-printing and SILAR (successive ionic layer adsorption reaction) methods. The films were used as photocatalysts for H2 generation using a solar simulator source. The incorporation of the SnS provokes the presence of particles of different morphology and size, allowing a better light absorption on the surface of the films. In addition, AuPd nanoparticles were deposited on the multilayer films to improve photocatalytic activity. XRD and TEM analysis revealed that whatever the proportion, the main phase is TiN. The SEM images showed that the electrostatic attraction between TiN and SnS is a key factor that influences the morphology of the films. The optical band-gap values for the films were similar (∼3.86 eV). According to profilometry measurements, the thickness of films varies from 218 to 887 nm, and PL results showed that when the thickness decreases the electron-hole pair recombination processes decrease too. The highest H2 generation was reached by T20:L80/SnS/AuPd, around 99 μmol/m2 after 3 h of irradiation, while T80:L20/SnS/AuPd produces only 33 μmol/m2, and coincidentally, showed lower and higher thickness, respectively. Moreover, the presence of AuPd nanoparticles did not provoke any structural and optical modification on the films. However, it caused the existence of active sites for H2 generation and diminish the electron-hole pair recombination, evidenced by PL analysis. Finally, these results corroborate that the film with a low thickness and higher LiAlSiO4 showed better photocatalytic activity because of the inhibition of the electro-hole pair recombination.

Influence of Annealing Temperature on the Properties of SILAR Deposited CdSe/ZnSe Superlattice Thin Films for Optoelectronic Applications

In this work, superlattice thin films of CdSe/ZnSe were fabricated on a non-conductive glass substrate using the successive ionic layer adsorption reaction (SILAR) method to investigate their properties for possible optoelectronic applications. The SILAR process involved a total cycle time of 100 seconds for a complete SILAR cycle with a total of 12 cycles made by depositing alternative layers of CdSe and ZnSe. The deposited thin films were annealed at different temperatures and characterized to determine their optical, elemental, morphological and structural properties using UV-VIS spectroscopy, Scanning electron microscope (SEM)/energy dispersive x-ray spectroscope (EDS) and x-ray diffraction techniques (XRD). The results of the characterizations revealed that optical properties of the films such as absorbance, reflectance, refractive index and extinction coefficient are low but increased as the annealing temperature increases. The bandgap energy was found to decrease from 2.50 eV-1.90 eV for as-deposited film and those annealed between 373 K and 523 K. film thickness was found to range from 130.169 nm to 254.441 nm. The EDS results showed that the target elements such as Cd, Zn, Se and other elements traceable to the nature of substrate used were found to be present in the deposited thin film samples. The results of the XRD showed that the thin films are polycrystalline and the diffraction peaks are influenced by annealing of the sample at a higher temperature such as 523 K. The crystal parameters such as crystallite size, dislocation density and micro-strain of the film at 523 K were found to be 5.546 nm, 3.25 × 1016 l/m2 and 1.13 × 10-2. The SEM results showed that the CdSe/ZnSe superlattice films were composed of tiny nanoparticles of different dimensions and sizes with hollow which increased as the annealing temperature increased from 432 K to 523 K. Possible applications of the deposited superlattice thin films in solar cells and optoelectronic devices were established by virtue of their bandgap energy and other properties.

0D-2D S-scheme CdS/WO3 catalyst for efficiently boosting CO2 photoreduction

Improving the dispersion of active sites and photogenerated carriers’ separation efficiency are of significant for enhancing the CO2 photoreduction. In this research, Zero-dimensional/Two-dimensional (0D-2D) S-scheme CdS/WO3 photocatalysts have been successfully obtained via the simple hydrothermal method and successive ionic layer adsorption reaction. SEM and TEM images provide that CdS Quantum Dots (QDs) are uniformly dispersed on the surface of WO3 nanosheets. WO3 nanosheets can greatly improve the dispersion of the CdS QDs, which can enlarge the adsorption and reaction efficiency of CO2 at the photoreduction sites. CO2 photoreduction tests show that the CdS/WO3 (CW-2) composite expresses excellent CO2 photoreduction ability and great catalytic stability. The yields of CO and CH4 with the CW-2 as catalyst are 64.7 μmol/g·h and 2.3 μmol/g·h, which are about 4.0 and 2.7 times more potent than that of CdS QDs. 13C calibration experiment proves that the C-source of CO and CH4 are obtained by the CO2 photoreduction process. Density functional theory calculation and electron spin resource results confirm the formation of S-scheme heterojunction. A potential synergistic effect of highly dispersed active sites and the S-scheme heterojunction has been provided for enhanced CO2 photoreduction performance.

Enhanced Photoelectrochemical Performance in Engineered Interface 2D Metal Sulfide Heterostructures for Water Splitting

Photoelectrochemical water splitting (PEC) is a viable solution for addressing future environmental and energy concerns. However, due to the high cost of photoelectrodes and the limitations of sluggish kinetics, practical applications are limited. To achieve that goal, effective solutions are still needed to create low-cost photoelectrodes suited for PEC. Transistion metal sulfides (TMS) materials have a high potential for use as photoelectrodes due to their favorable and impressive properties1. The photoactivity of TMS is typically unlimited due to low reflection at the grain boundary. The individual atomic thin sheets with higher surface area compared to bulk materials allow for faster diffusion of photoinduced charge carriers primarily due to the less interface between their grains. Their lower interfacial contact resistance enables enhanced charge dynamics and, as a result, improved electrochemical reaction kinetics. When compared to other TMS, CdS has a direct bandgap and excellent photoactivity. However, its toxicity and photocorrosion make it unsuitable for long-term practical use. WS2 is well-known layered transition metal sulfide that has a 2D molybdenite structure. It is non-toxic in acidic/neutral solutions that are chemically stable. It has been demonstrated to be more stable against oxidation and photo corrosion than CdS, which is extensively employed in photocatalysis2. However, because of the recombination of photoinduced charge carriers, pure WS2 exhibits relatively poor photocatalytic efficiency and stability. As a result, combining WS2 based photoactive nanomaterials with other suitable materials has helped overcome this challenge. Transistion metal sulfides with acceptable band structures for heterostructure construction with WS2 may enable breakthroughs in photocatalytic and photo-electrochemical processes.The primary focus of this work is to construct heterostructures by combining CdS and WS2 and to investigate their role as photoanodes of semiconductor materials in PEC water splitting. In this work, we have synthesised heterostructures using a facile solution-reaction method and Successive Ionic Layer Adsorption Reaction deposition (SILAR) technique which is intrinsically cost effective and scalable3. The heterostructure is characterised by XRD, SEM and TEM. We also studied the performance enhancement of this heterostructure using Linear sweep voltammetry and Electrochemical impedance spectroscopy. Pristine WS2 and CdS showed photocurrent densities of 3 μA cm-2 and 20 μA cm-2. However, heterostructures formation led to much improved photocurrents. Photocurrent densities of 151 μA cm-2 were observed for WS2/CdS heterostructures respectively at 1.23 V vs RHE. The enhanced improvement in photoelectrochemical performance in the case of the heterostructures could be due to the following factors: (a) the intimate interaction of this unique heterostructure improves adhesion and lowers the photoinduced charge transfer barrier; (b) increased light harvesting capability; and (c) improved charge dynamics of photoinduced charge carriers due to proper band alignment. The current study paves the way for further research into the creation of metal sulfide heterostructures that generate analogous photoelectrode materials.Keywords: Photoelectrochemical water splitting, metal sulfides, photoelectrodes.