Successive Ionic Layer Adsorption Research Articles

Enhanced charge carrier separation and stable photoelectrochemical water splitting via a high-performance BiVO4/BiOBr Type-II heterojunction

The development of an ideal photoanode that exhibits broad light absorption, efficient photogenerated carrier separation, and superior transmission efficiency remains a pivotal challenge in enhancing the sluggish photoelectrochemical (PEC) water splitting reaction. Here, we present an efficacious strategy to bolster the PEC performance of oxygen evolution by fabricating a BiVO4/BiOBr heterojunction through a combined electrochemical deposition-calcination approach and the successive ionic layer adsorption and reaction (SILAR) method. The band structure of BiOBr is optimally aligned with BiVO4, enabling the heterojunction to significantly enhance the separation efficiency of photogenerated charges and accelerate the kinetics of PEC water oxidation. Under simulated sunlight irradiation, the BiVO4/BiOBr heterojunction exhibits a remarkable photocurrent density of 2.69 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), surpassing the performance of bare BiVO4 film (0.46 mA/cm2 at 1.23 V vs. RHE) and demonstrating exceptional stability. This work offers novel insights into the rational design and fabrication of solar-driven PEC water splitting photoanodes.

Sensitization of AgInS2 nanoparticles enhances photoelectrochemical water splitting performance of CeO2 nanosheet arrays photoanode

In this study, we present a promising CeO2/AgInS2 heterostructure photoanode for photoelectrochemical (PEC) water decomposition. Mott-Schottky analysis is employed to confirm the formation of a type-II heterostructure between AgInS2 nanoparticles and CeO2 nanosheet arrays (NSAs) fabricated through electrochemical deposition and successive ionic layer adsorption and reaction. Electrochemical impedance spectroscopy, photoluminescence analysis, and Bode diagram spectroscopy confirm the effective charge carrier separation and significantly prolonged the charge lifetime of the CeO2/AgInS2 heterojunction photoanode. Consequently, the maximum photocurrent density of the constructed CeO2/AgInS2 photoanode relative to Ag/AgCl under zero bias test conditions is 69.8 times higher than the pure CeO2 NSAs. Additionally, the charge transfer mechanism is further verified by the calculated work function and differential charge density of CeO2/AgInS2 heterojunction. This study provides a valuable reference for the synthesis and preparation of heterojunction photoanode for efficient PEC water decomposition.

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.

Impact of different rinsing temperatures on SnS thin films created using the SILAR technique

The (SnS) thin films were prepared by Successive Ionic Layer Adsorption and Reaction (SILAR), a versatile and simple method. The cationic and anionic solutions SnCl2.2H2O and Na2S.9H2O respectively were used as precursor materials, which will be deposited on glass substrates to study the effect of rinsing temperature on the properties of our thin films. The structural, morphological, and optical properties were investigated by using X-ray diffraction, Energy Dispersive X-ray analysis (EDX), Scanning Electron Microscopy (SEM) and spectrophotometer. X-ray Diffraction (XRD) patterns indicated that the deposited SnS thin films have an orthorhombic crystal structure. Uniform deposition of the material over the entire glass substrate was shown by Scanning Electron Microscopy (SEM). The optical band gap energy ranged from 1.5 to 1.82eV for direct transitions and from 0.6 to 0.95eV for indirect transitions.

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 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.

Photodetector Devices: Investigation of ZnO Thin Films Fabricated via SILAR Technique on Various Substrates:

The synthesis of photodetectors for ZnO nanostructure films on various substrates, including p-type (100) silicon (Si), and porous silicon (pSi), has been achieved through the utilization of a straightforward technique known as the successive ionic layer adsorption and reaction (SILAR) method. To analyze the optical properties, surface morphology, and crystal structure of the ZnO layers, UV-Vis spectrometers, field emission scanning electron microscopes (FESEM), and X-ray diffraction (XRD) were employed. The characterization of the ZnO samples revealed that the number of SILAR cycles has a significant impact on the morphology and optical band gap of the synthesized layer. The Fourier-transform infrared (FTIR) spectrum successfully detected the distinctive extended vibration mode of ZnO. By conducting 20 cycles, high-quality hexagonal ZnO was obtained. The responsivity of the planar ZnO on silicon (ZnO/Si) and ZnO on the porous silicon (ZnO/pSi) surface exhibited variations depending on the substrate surface and bias voltage. The results indicated that the (ZnO/pSi) heterojunction demonstrated a high response in the visible range (350–850 nm) at a low bias voltage. On the other hand, the (ZnO/Si) photodetector displayed a high sensitivity of 666.66% at a low voltage of 1V in comparison to the (ZnO/pSi) photodetector, which exhibited a sensitivity of 483%.

Reduced Persistent Photoconductivity in Successive Ionic Layer Adsorption and Reaction‐Deposited ZnO:Sn Thin Films

Device‐quality Sn‐doped ZnO thin films are obtained from a simple and cost‐effective successive ionic layer adsorption and reaction method with doping concentrations of 1, 3, 5, and 7 mol%. The influence of doping on the structural, morphological, and optoelectronic properties is studied. All the samples show a hexagonal wurtzite structure with planes that reorient themselves upon doping. Morphological studies reveal sharp cone‐like structures branching out to become florets upon doping, resulting in a higher surface‐to‐volume ratio that is reflected in the photoresponse characteristics. The optical properties show a sharp absorbance edge, in the near‐UV region, for all the samples. The calculated bandgap is in the range of 3.19–3.23 eV. Photoluminescence spectra are recorded to analyze the defect states in the samples, and the native defects of ZnO are found. A remarkable increase in current is observed upon illumination indicating significant photoresponse. ZnO tends to show persistent photoconductivity wherein there is delayed decay in the photocurrent. This phenomenon is reduced significantly herein by doping with Sn atoms. The spectral response study confirms that the devices are suitable for visible‐blind, near‐UV detection.

Sequential growth controlled copper vanadate nanopebbles embedded thin films: Electrode to asymmetric supercapacitive device assembly

Supercapacitor performance critically relies on the design of electrodes with both superior electrochemical and mechanical properties. In this study, we present a cost-effective and scalable approach for the synthesis of copper vanadate (Cu3V2O8) nanopebbles integrated into a thin film, tailored for supercapacitor applications. The synthesis was accomplished using the successive ionic layer adsorption and reaction (SILAR) method, which enabled precise control over the deposition of Cu3V2O8 on a stainless steel (SS) substrate. Detailed structural, morphological, and elemental characterizations confirm the successful formation and reveal critical insights into the chemical bonding and oxidation state at material. The supercapacitive performance of Cu3V2O8 electrode has been evaluated in an aqueous NaClO4 electrolyte to assess pseudocapacitive behavior. The Cu3V2O8 electrode exhibited a specific capacitance of 443 F g−1 at 5 mV s−1 scan rate. Additionally, liquid configured an asymmetric device was designed using Multiwalled carbon nanotubes (MWCNT) combined with Cu3V2O8, yielding a specific capacitance of 116 F g−1 at 5 mV s−1 with an energy density of 8.43 Wh kg−1 and a power density of 345.4 W kg−1, while maintaining capacitance retention of 76 % even after 4000 cycles as stability test. This work highlights the potential of Cu3V2O8 based materials for excellent performance of new avenues for energy storage.

Enhancement of photodetector performance of aluminum-doped zinc oxide thin films fabricated via SILAR method: Structural, optical, and electrical analysis

This study presents a comprehensive analysis of the structural, optical, electrical, and photosensing characteristics of aluminum-doped zinc oxide (Al:ZnO) thin films, fabricated via successive ionic layer adsorption and reaction (SILAR) techniques. The Raman and X-ray diffraction (XRD) analyses validated the hexagonal wurtzite structure and revealed that Al doping enhances crystallinity and crystal growth of ZnO. The average crystallite size increased from 21.6 nm in undoped sample to 23.8 nm in 5.0 wt% Al-doped sample, while strain effects decreased from 4.67 × 10-3 to 4.36 × 10-3. Scanning electron microscopy (SEM) images revealed improved film morphology and more defined geometries with increased Al doping, while energy-dispersive X-ray analysis (EDAX) confirmed successful Al integration into the ZnO lattice. Optical analyses indicate a narrowing of the ZnO bandgap to 2.81 eV in 5.0 wt% Al:ZnO from 3.02 eV in the undoped variant, while photoluminescence (PL) peak positions remains unchanged. Time-resolved fluorescence (TRF) indicated a reduction in electron lifetime with higher Al doping. Furthermore, Hall effect assessments reveal a decrease in carrier mobility and electrical resistivity, alongside a rise in carrier concentration with higher Al content. The photodetection efficacy was substantially improved with Al doping, particularly at 2.5 wt% Al, achieving a responsivity of 42.5 × 10-2 A/W, external quantum efficiency of 99.3 %, and detectivity of 1.8 × 1011 Jones. These findings exhibit that Al-doping substantially enhances the photodetection properties of ZnO thin films.

Facile SILAR deposited SnS/NiS vertical heterojunction for high performance flexible broadband photodetector

Low-cost, flexible broadband photodetectors fabricated from two-dimensional transition metal chalcogenides have garnered attention because of their excellent absorption coefficient and photoconductivity. Likewise, vertical heterojunctions fabricated from two two-dimensional (2D) transition metal chalcogenides (TMCs) also have drawn major curiosity lately owing to their superior optical performance. This work reports a p-p type II vertical Van der Waal's heterojunction structure by depositing thin film of NiS over SnS on a flexible paper substrate. Morphological and structural characterization confirms presence of a rhombohedral β-NiS crystal structure along with traces of Ni(OH)2 on orthorhombic SnS nanoparticles. The device fabrication method made use of the inexpensive, clean room free SILAR (Successive Ionic Layer Adsorption and Reaction) technique. A purposeful modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment. The fabricated device records optical responsivity of 0.92 mA/W under UV illumination, 5.32 mA/W under Visible illumination, and 0.8 mA/W under NIR illumination. A maximum EQE of 1.3 % is observed along with superior response times of 0.114 s (UV),0.103 s (Visible) and 1.34 s (NIR). The acquired photo response is due to superior absorption property of NiS in UV region and SnS in the visible and NIR region. The difference in fermi level between two materials causes efficient separation of the charge carriers that results in junctional electric field upon light illumination. The device underwent flexibility testing and shown exceptional resistance to bending force making it suitable for numerous applications like wearable healthcare monitoring, security purposes and flexible image sensors.

SILAR deposited Antiviral silver-doped Ceria nano-films

Amid the COVID-19 global pandemic, ceria nanomaterials (CN) have garnered renewed interest as potential antiviral agents due to their ability to generate reactive oxygen species (ROS) on their surfaces. Enhancing ROS generation through precise defect engineering is key to improving these antiviral properties. This can be achieved through various methods, such as altering nano-dimensions and doping. In this context, we report on silver-doped ceria thin films. We have employed a cost-effective SILAR (Successive Ionic Layer Adsorption and Reaction) method for ceria nano-film deposition, which offers excellent control over film thickness. Utilizing an Arduino-controlled layer-by-layer (LBL) setup, we achieved precise control over the deposition process. This method facilitated the easy doping of ceria nano-films with silver ions. The silver-doped SILAR ceria thin films of varying thicknesses were subjected to antibacterial testing against E. coli bacteria. The samples with the highest antibacterial activity were further tested for antiviral efficacy against Feline calicivirus. The 80 SILAR Layers Ag-Ceria sample exhibited the best activity, completely deactivating the viral titer (105). This sample, when further tested against OC43 coronavirus, demonstrated a >99% reduction in virus titer. The mechanisms underlying these antimicrobial properties were investigated using antioxidative testing assays.

Analyzing antimicrobial activity of ZnO/FTO, Sn-Cu-doped ZnO/FTO thin films: Production and characterizations.

In the developing field of nanotechnology, ZnO (zinc oxide) based semiconductor samples have emerged as the foremost choice due to their immense potential for advancing the development of cutting-edge nanodevices. Due to its excellent chemical stability, low cost, and non-toxicity to biological systems, it is also utilized in various investigations. In this study, the successive ionic layer adsorption and reaction (SILAR) method was used to generate FTO (fluorine-doped tin oxide)/ZnO, and tin (Sn)-copper (Cu)-doped ZnO thin films at varying concentrations on FTO substrates. After being stacked 40 times in varying concentrations on the FTO substrate, FTO/ZnO thin films and Sn-Cu-doped thin films were annealed at 300°C. Using Scanning Electron Microscopy (SEM) Energy Dispersive Spectroscopy-(EDS), the agar diffusion test, and the viability cell counting method, the minimum inhibitory concentration, structural properties, surface morphology, antibacterial properties, bacterial adhesion, and survival organism count of FTO/ZnO thin films and Sn-Cu-doped thin films were investigated. Both doped and FTO/ZnO films with varying Sn-Cu concentrations expanded harmonically on the FTO substrate, according to the SEM-EDS investigation. The doping concentration affected their morphological properties, causing changes depending on the doping level. Antibacterial activity was observed in the powder metals, but no antibacterial activity was found in the thin film form. The highest adhesion rate of bacterial organisms on the produced samples was observed when the FTO/ZnO/Sn-Cu doping rate was 1%. In addition, the lowest adhesion rate was observed when the FTO/ZnO/Sn-Cu additive ratio was 3%. RESEARCH HIGHLIGHTS: ZnO based semiconductors highlight significant potential in advancing nanodevice technology due to their chemical stability, cost-effectiveness, and biocompatibility. Employing the SILAR method, the study innovatively fabricates FTO/ZnO and Sn-Cu-doped ZnO thin films on FTO substrates, exploring a novel approach in semiconductor manufacturing. Post annealing at 300°C, the research examines the structural and surface morphological changes in the films, contributing to the understanding of semiconductor behavior under varying conditions. The study delves into the antibacterial properties of ZnO thin films, offering insights into the potential biomedical applications of these materials. SEM-EDS analysis reveals that doping concentrations crucially influence the morphological properties of ZnO thin films, shedding light on the optimization of semiconductor performance. Findings indicate a specific doping rate (1% Sn-Cu) enhances bacterial adhesion, while a 3% additive ratio minimizes it, suggesting implications for biomedical device engineering and antibacterial surface design.

Performance evaluation of SILAR deposited Rb-Doped ZnO thin films for photodetector applications

ZnO-based photodetectors (PDs) compose a remarkable optoelectronic device field due to their high optical transmittance, electrical conductivity, wide band gap, and high binding energy. This study examined the visible light photodetector performance of the pristine and Rubidium (Rb)-doped ZnO thin films. The influence of Rb doping amount (2, 4, and 6 wt% in solution) on the electrical, optical, and structural properties of the ZnO-based thin films produced by the Successive Ion Layer Adsorption and Reaction (SILAR) technique was analyzed. Structural analyses showed that all peaks correspond to hexagonal wurtzite structure with no other peak from Rb-based phases, suggesting the high quality of the crystalline pristine and Rb-doped ZnO thin films. The morphology of the thin films shows homogenous layers formed of nanoparticles where particle size was first decreased and then increased with the increasing Rb doping according to Scanning Electron Microscope (SEM) morphology analysis. Besides that, Raman spectroscopy analyses indicate that the phonon lifetimes of the ZnO-based thin films slightly increased due to the improvement of the crystal quality with the increasing amount of Rb in the SILAR solution. Photosensor measurements of the nanostructured pristine and Rb-doped ZnO thin films were measured at different light power intensities under the visible light environment. Photosensor properties were examined depending on the doping amount and light power density. In light of the literature review, our study is the first to produce Rb-doped ZnO thin films via the SILAR method, which has a promising potential for photosensor applications.Graphical

Interfacial Engineering of BiVO4/Bi2Mo2O9 Heterojunction Toward Photogenerated Carriers Anisotropic Transfer

Developing an advanced strategy to decrease the charge recombination of BiVO4 is a vital requirement to boost charge transfer for photoelectrochemical water oxidation. Herein, a type II BiVO4/Bi2Mo2O9 heterojunction is successfully synthesized on fluorine‐doped tin oxide substrate by successive ionic layer adsorption and reaction method. Thanks to the Fermi‐level energy difference of 275 mV between BiVO4 and Bi2Mo2O9, an outward built‐in electric filed pointing from Bi2Mo2O9 to BiVO4 is induced, which accelerates the directional flowing of photogenerated electron and hole. Such a unique design structure fastens the electron migration from BiVO4 to Bi2Mo2O9, and the holes will transfer to the surface to participate in water oxidation. The longer lifetime (9.2 ns) by time‐resolved transient photoluminescence signifies that the Bi2Mo2O9 can boost interfacial carriers’ anisotropic migration; the surface charge transfer rate of BiVO4/Bi2Mo2O9 is up to 387.6 s−1 (1.4 V vs reversible hydrogen electrode (RHE)). The BiVO4/Bi2Mo2O9 heterojunction exhibits a remarkable charge separation efficiency of 64% and outstanding photocurrent density of 0.9 mA cm−2 at 1.23 V versus RHE.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

Impact of deposition parameters on the optical properties of Fe2O3 thin films prepared by SILAR method

In order to explore the structures, morphology, and optical features of Fe2O3 nanofilms, the successive ionic layer adsorption and reactions (SILARs) technique was utilized to deposit the nanofilms onto glassy slides at varying concentrations of the precursor. Three precursor concentrations (0.025, 0.05 and 0.075) M were used. Analysis using X-ray diffraction (XRD) presented the crystalline structure of the Fe2O3 thin films. Field emission-scanning electron microscopy (FE-SEM) was used to evaluate the morphological features of the films. The results demonstrate that the surfaces of the films are nonporous and that there is a good distribution for spherical nanosize particles. The number of cycles is another important parameter that has been tested and its effect on the optical properties of prepared films was evaluated. The optical properties like optical absorption and energy gaps are affected directionally by changing the concentration and cycle numbers during the preparation. The latest objective of our study is to determine the role of precursor concentrations and deposition cycles in preparing thin films that have electronic applications such as sensors and solar cells.

Synthesis of Bi2S3-sensitized TiO2 photoanodes for enhanced photovoltaic performance in solar cell application

The synthesis of Bi2S3 nanoparticles for sensitizing TiO2 photoanodes were synthesized through a cost-effective and straightforward approach using modified chemical bath deposition (M-CBD) or successive ionic atomic layer adsorption reactions (SILAR) at room temperature. Initially, a TiO2 seed layer was synthesized at room temperature via the chemical bath deposition method, followed by deposition of a mesoporous TiO2 layer using the doctor blade method. This study investigated the influence of the number of SILAR cycles and the choice of counter electrodes on the performance of Bi2S3/TiO2-based photoelectrodes. Characterization of the prepared Bi2S3/TiO2 photoanode involved various techniques, including X-ray diffraction, UV–Vis spectroscopy, scanning electron microscopy, and Raman spectroscopy, enabling the analysis of its structural, optical, and morphological properties. The Bi2S3/TiO2-based cell exhibits a maximum conversion efficiency of 0.8%, demonstrating the potential of this combination for photovoltaic applications. This study contributes to the field of solar cell technology by presenting a novel approach for sensitizing TiO2 photoanodes with Bi2S3 nanoparticles, offering insights into the optimization of fabrication parameters and performance enhancement strategies for future device design and development.

Influence of solution pH dependency on structure, optical with photoelectrochemical characteristics of SILAR deposited copper oxide thin films

Photoelectrochemical (PEC) technology is a promising approach for converting solar energy into chemical energy, offering significant potential for renewable energy applications. In this work, the CuO thin film was fabricated with different pH value in between 8.5 ± 0.1 and 10.5 ± 0.1 via Successive Ionic Layer Adsorption and Reaction (SILAR) method. The Effect of pH on thickness, structural, morphological, elemental composition and optical properties were investigated by using stylus profilometry, XRD, SEM, TEM, EDX, UV–vis and PL. The XRD results showed that as the pH increased, the crystallite size increased from 19.24 nm to 25.62 nm, with a monoclinic phase along the (111) direction. The CuO film deposited at pH value 10.5 ± 0.1 exhibit well defined identical particle with its size in the range between 200 and 300 nm was confirmed by SEM and TEM analysis. As the pH increased from 8.5 ± 0.1 to 10.5 ± 0.1, the CuO film bandgap (Eg) value reduced from 1.52 eV to 1.42 eV with indirect transition. The CuO photocathode deposited at pH 10.5 ± 0.1 shows maximum photocurrent density of 1.45 mA/cm2 at −0.1 V vs. RHE in 0.5 M Na2SO4 solution. Furthermore, the Electrochemical Impedance Spectroscopy (EIS) analysis shows, the CuO (pH 10.5 ± 0.1) electrode have higher conductivity value of 0.6862 S/cm compared CuO at pH 8.5 ± 0.1 (0.2779 S/cm) and CuO at pH 9.5 ± 0.1 (0.4646 S/cm) electrodes.

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.

Design strategy of TiO2/AgInSe/CdS/CdSe/ZnS photoanode and optimization of CdSe nanoparticles layer for increasing the efficiency of quantum dot-sensitized solar cells

In this study, ternary AgInSe (AISe) quantum dots compound were synthesized using a novel chemical precipitation method followed by a controlled hydrothermal treatment. The as-prepared particles were deposited onto a mesoporous TiO2 substrate to be applied as the photoelectrode of quantum dot sensitized solar cells (QDSSCs). Two configurations of multilayer photoanodes i.e. the TiO2 NCs/AgInSe/CdS/ZnS and TiO2 NCs/AgInSe/CdS/CdSe/ZnS were fabricated and employed for higher photovoltaic performance. The co-sensitizing CdS and CdSe nanocrystals layers were synthesized and deposited through successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) techniques, respectively. The results revealed that the QDSSCs with TiO2 NCs/AgInSe/ZnS photoanode initially showed an efficiency of 0.45 %. Incorporating CdS NCs as a quasi-shell film increased the efficiency to 3.9 % in the optimized TiO2/AgInSe/CdS(3 cycle)/ZnS configuration. Adding CdSe nanocrystals over-layer did not improve the efficiency of corresponding cells due to the increased thickness and resistance. Instead, the TiO2/AgInSe/CdS(2 cycle)/CdSe(12 min)/ZnS photoanode resulted in the efficiency of 4.10 % with 34 % improvement. Using the sub-micron size TiO2 hollow spheres (HSs) as the light scattering layer created further light absorption and enhanced performance. It was shown that the photovoltaic parameters were increased to short circuit current density (Jsc) of 23.25 mA/cm2, open-circuit voltage (Voc) of 512 mV and overall efficiency equal to 4.55 %