scholarly journals Boosting the Activity and Stability of Copper Tungsten Nanoflakes toward Solar Water Oxidation by Iridium-Cobalt Phosphates Modification

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 913
Author(s):  
Chao Li ◽  
Peng Diao
Keyword(s):  
Water Oxidation ◽  
Collection Efficiency ◽  
Potassium Phosphate ◽  
Photocurrent Density ◽  
Charge Transfer Resistance ◽  
Buffer Solution ◽  
Hydrogen Electrode ◽  
Electron Hole ◽  
Transfer Resistance ◽  
Hole Recombination

Severe interfacial electron–hole recombination greatly limits the performance of CuWO4 photoanode towards the photoelectrochemical (PEC) oxygen evolution reaction (OER). Surface modification with an OER cocatalyst can reduce electron–hole recombination and thus improve the PEC OER performance of CuWO4. Herein, we coupled CuWO4 nanoflakes (NFs) with Iridium–cobalt phosphates (IrCo-Pi) and greatly improved the photoactivity of CuWO4. The optimized photocurrent density for CuWO4/IrCo-Pi at 1.23 V vs. reversible hydrogen electrode (RHE) rose to 0.54 mA∙cm−2, a ca. 70% increase over that of bare CuWO4 (0.32 mA∙cm−2). Such improved photoactivity was attributed to the enhanced hole collection efficiency, which resulted from the reduced charge-transfer resistance via IrCo-Pi modification. Moreover, the as-deposited IrCo-Pi layer well coated the inner CuWO4 NFs and effectively prevented the photoinduced corrosion of CuWO4 in neutral potassium phosphate (KPi) buffer solution, eventually leading to a superior stability over the bare CuWO4. The facile preparation of IrCo-Pi and its great improvement in the photoactivity make it possible to design an efficient CuWO4/cocatalyst system towards PEC water oxidation.

Metal Doped TiO2 Photocatalysts for CO2 Photoreduction

2013 ◽  
Vol 757 ◽  
pp. 243-256 ◽  
Author(s):  
Amir Al-Ahmed
Keyword(s):  
Chemical Reactions ◽  
Water Oxidation ◽  
Active Species ◽  
Electron Hole ◽  
Highly Active ◽  
Redox Active ◽  
Recent Developments ◽  
Metal Doped ◽  
Generate Electron ◽  
Hole Recombination

Greenhouse gases such as CO2, CH4 and CFCs are the primary causes of global warming. Worldwide, people are exploring techniques to reduce, capture, store CO2 gas and even convert this gas in to some useful chemicals. CO2 can be transformed into hydrocarbons in a photocatalytic reaction. The advantage of photo reduction of CO2 is to use inexhaustible solar energy. Knowledge of elementary steps in photocatalytic CO2 reduction under UV irradiation is required in order to improve the photo efficiency of the photocatalyst. A semiconductor photocatalyst mediating CO2 reduction and water oxidation needs to absorb light energy, generate electron hole pairs, spatially separate them, transfer them to redox active species across the interface and minimize electron hole recombination. This requires the semiconductor to have its conduction band electrons at higher energy compared to the CO2 reduction potential while the holes in the valence band need to be able to oxidize water to O2. A single semiconductor does not usually satisfy these requirements. Some recent developments in this field have been moves towards rational photocatalyst design, the use of highly active isolated Ti-species in mesoporous and microporous materials, metal-doping of TiO2, development of catalysts active at longer wavelengths than can be achieved with commercially available titania etc. The use of transition-metal loaded titanium dioxide (TiO2) has been extensively studied as a photocatalyst in photoreactions. Unlike traditional catalysts drive chemical reactions by thermal energy, semiconducting photocatalysts can induce chemical reactions by inexhaustible sunlight and convert CO2 in to the useful hydrocarbons. In this review article we will cover different aspects of metal doped nano structured TiO2 photocatalysts, used to convert/reduce CO2 in to useful hydrocarbons.

Interface engineering of perovskite solar cells with PEO for improved performance

2015 ◽  
Vol 3 (18) ◽  
pp. 9999-10004 ◽  
Author(s):  
H. P. Dong ◽  
Y. Li ◽  
S. F. Wang ◽  
W. Z. Li ◽  
N. Li ◽  
...  
Keyword(s):  
Solar Cells ◽  
Collection Efficiency ◽  
Perovskite Solar Cells ◽  
Device Performance ◽  
Interface Engineering ◽  
Electron Hole ◽  
Electron Collection ◽  
Improved Performance ◽  
Hole Recombination ◽  
Electron Collection Efficiency

A thin PEO layer was spin-coated on top of TiOx to modify the ETL for improved electron collection efficiency and better retarded electron–hole recombination, and therefore enhance device performance.

Nanostructured Composite Catalyst for Electrochemical Water Splitting: Significantly Improved for Hydrogen Evolution Reaction

2020 ◽  
Vol 18 (11) ◽  
pp. 842-852
Author(s):  
Abdul Qayoom Mugheri ◽  
Muhammad Soomar Samtio ◽  
Shahzad Ahmed Memon
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Water Oxidation ◽  
Rational Design ◽  
Real Life ◽  
Charge Transfer Resistance ◽  
Composite Catalyst ◽  
Life Transition ◽  
Transfer Resistance ◽  
Nanostructured Composite

The evolutionary and rational design we incorporated for an efficient nonprecious metal nanocom-posite electrocatalysts for the hydrogen production which is a scientific challenge in the field of renewable energy. Herein, we report a simple and very active, the functional electrocatalyst for water oxidation which is highly demanded. It is of great prime importance for hydrogen evolution reaction (HER) which significantly contributes to renewable technologies. The values for electrocatalysts are NiCo2O4 and NiCo2O3/P Tafel slope 66 and 42 mV/decade and overpotential of 382 and 320 mV and current density achieved at 10 mA/cm2 anin 1.0 M KOH. The composites are characterized by SEM, HR-TEM, X-ray diffraction, XPS, and SAED. The NiCo2O3/P having high durability measured for 50 hours and its EIS results holding a small charge transfer resistance 28.81 Ohms (Ω) and capacitance containing 0.81 mF. Finally, we give an outlook for the development of these nanoma-terials in the short- and mid-term, highlighting the critical challenges to confront for a lab-to-real life transition of these highly promising nanocomposites.

scholarly journals Study of solvent effect on structural and photoconductive behavior of ternary chalcogenides InBiS3-In2S3-Bi2S3 composite thin films deposited via AACVD

2019 ◽  
Vol 42 (1) ◽  
pp. 102-112 ◽  
Author(s):  
Umar Daraz ◽  
Tariq Mahmood Ansari ◽  
Shafique Ahmad Arain ◽  
Muhammad Adil Mansoor ◽  
Muhammad Mazhar
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Visible Region ◽  
Chloroform Solution ◽  
Photocurrent Density ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
X Ray ◽  
Wide Range

Abstract In the present work ternary composite InBiS3-In2S3-Bi2S3 (IBS) thin films are developed using a homogeneous mixture of precursors [Bi(S2CN(C2H5)2)3]2 (1) and [In(S2CNCy2)3]‧2py (2), separately in toluene and chloroform solutions at 500°C under an inert atmosphere of argon gas via aerosol assisted chemical vapor deposition (AACVD) technique. The phase purity, chemical composition and morphological study of both the films deposited from toluene and chloroform solutions are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Field emission scanning electron microscopy (FESEM). The surface morphology showed rod like structure of the films developed from toluene while the films grown from chloroform solution give flake like shapes. The UV-visible spectroscopy explicated that the thin films developed from toluene and chloroform solutions show wide range absorption in whole visible region. Linear Scan voltammetry results show that both the films give negligible dark current, however, the films fabricated from toluene solution give a sharp steep curve with maximum photocurrent density of 2.3 mA‧cm-2 at 0.75 V vs Ag/AgCl/3M KCl using 0.05 M sodium sulphide solution under AM 1.5 G illumination (100 mW‧cm-2), while the film grown from chloroform generates a photocurrent density of 2.1 mA‧cm-2 under similar conditions. The LSV outcomes are further supported by electrochemical impedance spectroscopy (EIS) that gives charge transfer resistance (Rct) value of 8,571 Ω for the films developed from toluene as compared to films fabricated from chloroform with Rct value of 12,476 Ω.

scholarly journals Multilayer WO3/BiVO4 Photoanodes for Solar-Driven Water Splitting Prepared by RF-Plasma Sputtering

Surfaces ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 105-115 ◽  
Author(s):  
Matteo Pedroni ◽  
Gian Luca Chiarello ◽  
Espedito Vassallo ◽  
Elena Selli
Keyword(s):  
Water Splitting ◽  
Photocurrent Density ◽  
Rf Plasma ◽  
Back Side ◽  
Time Stability ◽  
Electron Hole ◽  
Plasma Sputtering ◽  
Innermost Layer ◽  
Carrier Separation ◽  
Hole Recombination

A series of WO3, BiVO4 and WO3/BiVO4 heterojunction coatings were deposited on fluorine-doped tin oxide (FTO), by means of reactive radio frequency (RF) plasma (co)sputtering, and tested as photoanodes for water splitting under simulated AM 1.5 G solar light in a three-electrode photoelectrochemical (PEC) cell in a 0.5 M NaSO4 electrolyte solution. The PEC performance and time stability of the heterojunction increases with an increase of the WO3 innermost layer up to 1000 nm. A two-step calcination treatment (600 °C after WO3 deposition followed by 400 °C after BiVO4 deposition) led to a most performing photoanode under back-side irradiation, generating a photocurrent density of 1.7 mA cm−2 at 1.4 V vs. SCE (i.e., two-fold and five-fold higher than that generated by individual WO3 and BiVO4 photoanodes, respectively). The incident photon to current efficiency (IPCE) measurements reveal the presence of two activity regions over the heterojunction with respect to WO3 alone: The PEC efficiency increases due to improved charge carrier separation above 450 nm (i.e., below the WO3 excitation energy), while it decreases below 450 nm (i.e., when both semiconductors are excited) due to electron–hole recombination at the interface of the two semiconductors.

scholarly journals Transferred monolayer MoS2 onto GaN for heterostructure photoanode: Toward stable and efficient photoelectrochemical water splitting

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mostafa Afifi Hassan ◽  
Min-Woo Kim ◽  
Muhammad Ali Johar ◽  
Aadil Waseem ◽  
Min-Ki Kwon ◽  
...  
Keyword(s):  
Water Splitting ◽  
Alternative Energy ◽  
Chemical Vapor ◽  
Photocurrent Density ◽  
Charge Transfer Resistance ◽  
Photoelectrochemical Water Splitting ◽  
Organic Chemical ◽  
Transfer Resistance ◽  
Alternative Energy Sources ◽  
New Perspective

AbstractSolar-driven photoelectrochemical water splitting (PEC-WS) using semiconductor photoelectrodes is considered a promising solution for sustainable, renewable, clean, safe and alternative energy sources such as hydrogen. Here, we report the synthesis and characterization of a novel heterostructure MoS2/GaN to be used as a photoanode for PEC-WS. The heterostructure was synthesized by metal-organic chemical vapor deposition of single crystalline GaN onto a c-plane sapphire substrate, followed by the deposition of a visible light responding MoS2 monolayer (Eg = 1.9 eV) formed by a Mo-sulfurization technique. Our experimental results reveal that MoS2/GaN photoanode achieved efficient light harvesting with photocurrent density of 5.2 mA cm−2 at 0 V vs Ag/AgCl, which is 2.6 times higher than pristine GaN. Interestingly, MoS2/GaN exhibited a significantly enhanced applied-bias-photon-to-current conversion efficiency of 0.91%, whereas reference GaN yielded an efficiency of 0.32%. The superior PEC performance of the MoS2/GaN photoelectrode is mainly related to the enhanced light absorption due to excellent photocatalytic behavior of MoS2, which reduces charge transfer resistance between the semiconductor and electrolyte interface, and the improvement of charge separation and transport. This result gives a new perspective on the importance of MoS2 as a cocatalyst coated onto GaN to synthesize photoelectrodes for efficient solar energy conversion devices.

scholarly journals Fabrication, characterization, and photocatalytic performance of ternary cadmium chalcogenides CdIn2S4 and Cd7.23Zn2.77S10-ZnS thin films

2020 ◽  
Vol 44 (1) ◽  
pp. 39-50
Author(s):  
Umar Daraz ◽  
Tariq Mahmood Ansari ◽  
Shafique Ahmad Arain ◽  
Muhammad Adil Mansoor ◽  
Muhammad Mazhar ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Chemical Vapor ◽  
Linear Sweep Voltammetry ◽  
Photocurrent Density ◽  
Charge Transfer Resistance ◽  
Single Step ◽  
Transfer Resistance ◽  
X Ray ◽  
Dual Source

Abstract Dithiocarbamate complexes [Cd(S2CNCy2)2(py)] (1), [In(S2CNCy2)3]·2py (2) and [Zn(S2CNCy2)2(py)] (3) were synthesized and toluene solution of (1) and (2) was used as dual source precursor for the synthesis of CdIn2S4 (CIS), while that of (1) and (3) was applied for the deposition of Cd7.23Zn2.77S10–ZnS composite (CZS-ZS) thin film photoan-odes by employing single step aerosol assisted chemical vapor deposition (AACVD) technique. Deposition experiments were performed at 500°C under an inert ambient of argon gas. The structural properties of deposited films were evaluated by using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The field emission scanning electron microscopy (FESEM) exposed surface morphologies while UV-Visible spectrophotometry revealed that CIS is low band gap photoanode in comparison to CZS-ZS. The comparison of photoelectrochemical (PEC) responses measured in identical conditions in terms of linear sweep voltammetry (LSV) depicts photocurrent density of 4.4 mA /cm2 and 2.9 mA/cm2 at applied potential of 0.7 V under solar light intensity of 100 mW/cm2 for CIS and CZS-ZS respectively. Further, electrochemical impedance spectroscopy (EIS) confirms that PEC properties of CIS are superior to CZS-ZS photoanode as the former offer less charge transfer resistance (Rct) 0.03 MΩ in comparison to CZS-ZS having Rct value of 0.06 MΩ.

scholarly journals Preparation of nanoporous BiVO 4 /TiO 2 /Ti film through electrodeposition for photoelectrochemical water splitting

2018 ◽  
Vol 5 (9) ◽  
pp. 180728 ◽  
Author(s):  
Dong Hongxing ◽  
Liu Qiuping ◽  
He Yuehui
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Saturated Calomel Electrode ◽  
Photocurrent Density ◽  
Charge Transfer Resistance ◽  
Photoelectrochemical Properties ◽  
Photocatalytic Efficiency ◽  
Transfer Resistance ◽  
Electrodeposition Time ◽  
Absorption Studies

A nanoporous BiVO 4 /TiO 2 /Ti film was successfully fabricated by electrodepositing a nanoporous BiOI film on nanoporous TiO 2 arrays followed by annealing at 450°C for 2 h. The electrodeposition of BiOI film was carried out at different times (10, 30, 100, 500 and 1000 s) in Bi(NO 3 ) 3 and KI solution. The morphological, crystallographic and photoelectrochemical properties of the prepared BiVO 4 /TiO 2 /Ti heterojunction film were examined by using different characterization techniques. UV–vis spectrum absorption studies confirmed an increase in absorption intensities with increasing electrodeposition time, and the band gap of BiVO 4 /TiO 2 /Ti film is lower than that of TiO 2 /Ti. The photocatalytic efficiency of BiVO 4 /TiO 2 /Ti heterojunction film was higher compared to that of the TiO 2 /Ti film owing to the longer transient decay time for BiVO 4 /TiO 2 /Ti film (3.2 s) than that of TiO 2 /Ti film (0.95 s) in our experiment. The BiVO 4 /TiO 2 /Ti heterojunction film prepared by electrodeposition for 1000 s followed by annealing showed a high photocurrent density of 0.3363 mA cm −2 at 0.6 V versus saturated calomel electrode. Furthermore, the lowest charge transfer resistance from electrochemical impedance spectroscopy was recorded for the BiVO 4 /TiO 2 /Ti film (1000 s) under irradiation.

scholarly journals Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation

2014 ◽  
Vol 5 (8) ◽  
pp. 2964-2973 ◽  
Author(s):  
Yimeng Ma ◽  
Stephanie R. Pendlebury ◽  
Anna Reynal ◽  
Florian Le Formal ◽  
James R. Durrant
Keyword(s):  
Absorption Spectroscopy ◽  
Water Oxidation ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Electron Hole ◽  
Solar Water ◽  
Solar Water Oxidation ◽  
Oxidation Efficiency ◽  
Hole Recombination

We use transient absorption spectroscopy and photoelectrochemical methods to study the dynamics of photogenerated holes in BiVO4 for solar water oxidation. The back electron/hole recombination is found to be slow and therefore competes with water oxidation, limiting water oxidation efficiency.

scholarly journals Structural, Optical, Band Edge and Enhanced Photoelectrochemical Water Splitting Properties of Tin-Doped WO3

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 456 ◽  
Author(s):  
Shankara S. Kalanur
Keyword(s):  
Water Splitting ◽  
Charge Transfer Resistance ◽  
Band Edge ◽  
Hydrogen Electrode ◽  
Facile Hydrothermal Method ◽  
Transfer Resistance ◽  
Substitutional Doping ◽  
Energy Distance ◽  
Wo3 Thin Films ◽  
Pec Water Splitting

The substitutional doping of tungsten oxide (WO3) with metal ions demonstrates a promising approach to enhance its photoelectrochemical (PEC) water splitting efficiency. In this article, the substitutional doping of Sn ions into WO3 lattice and its effect on optical, electrical, band edge, and PEC water splitting properties are explored. Sn-doped WO3 thin films were synthesized using a facile hydrothermal method. The characterization data reveal that the doping of Sn alters the morphology, induces multiple crystal phases, effects the crystal orientation, reduces the band gap, and increases the carrier density of WO3. With the uniform distribution of Sn ions in WO3 and the decreased charge transfer resistance at the electrode/electrolyte interface, the doped WO3 show notable enhancement in its PEC activity compared to the undoped WO3. The band edge study revealed that the introduction of Sn in WO3 lattice causes an increase in the energy distance between the valence band edge and Fermi level and, at the same time, induces a downward shift in both the valence and conduction band edges towards higher potentials with respect to reversible hydrogen electrode (RHE). Conclusively, this work shows significant and new insights about Sn-doped WO3 photoanodes and their influence on PEC water splitting efficiency.

Sign in / Sign up

Export Citation Format

Share Document