Photoelectrochemical properties of texture-controlled nanostructured α-Fe2O3 thin films prepared by AACVD

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Nanostructured α-Fe2O3 thin film electrodes were deposited by aerosol-assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α-Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current-voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 μA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C

Fabrication of Bi2 WO6 photoelectrodes with enhanced photoelectrochemical and photocatalytic performance

This is the final version. Available from Elsevier via the DOI in this record.Visible light active semiconductor Bi 2 WO 6 photoelectrodes with desired physical and chemical properties are sought for solar energy conversion and photocatalytic applications. The porous nanostructured Bi 2 WO 6 photoelectrodes are prepared by Spray Pyrolysis (SP). A detail study has been conducted to correlate the annealing temperature, morphology and crystallographic orientation with the photoelectrochemical (PEC), electrochemical and photocatalytic properties. The photoelectrodes possess an optical bandgap of 2.82 eV and exhibit anodic photocurrent. The current-voltage characterization of Bi 2 WO 6 photoelectrodes reveals that the photocurrent density and photocurrent onset potential is strongly dependent on the deposition parameters. The PEC study shows that the photoelectrode annealed at 525 °C has photocurrent density of 42 μAcm −2 at 0.23 V (vs Ag/AgCl/3M KCl) under AM1.5 illumination and exhibit superior photocatalytic activity for Rhodamine B (RhB) degradation. The electrochemical study shows that the photoelectrode has flatband potential of 2.85 V which is in good agreement with photocurrent onset potential. This finding will have a significant influence on further exploitation of Bi 2 WO 6 as a potential semiconductor material in solar energy conversion and photocatalytic applications.The Saudi Arabian Cultural BureauEngineering and Physical Sciences Research Council (EPSRC

Electrocatalytic activity of CoFe2O4 thin films prepared by AACVD towards the oxygen evolution reaction in alkaline media

© 2017 The Authors The electrocatalytic behaviour of CoFe 2 O 4 thin films, prepared by aerosol-assisted chemical vapour deposition, towards the oxygen evolution reaction in an alkaline medium is reported. X-ray diffraction and SEM data show that the CoFe 2 O 4 thin films are phase pure and consist of dendrites 0.5–1 μm in diameter rising from the surface with heights ranging from 1 to 3 μm. The CoFe 2 O 4 thin films exhibited an overpotential of 490 mV at a current density of 10 mA cm − 2 , and a Tafel slope of 54.2 mV dec − 1 . Taking into account the electrochemically active surface area, the intrinsic activity of CoFe 2 O 4 was found to be 1.75 mA cm − 2 real at an overpotential of 490 mV. The CoFe 2 O 4 thin films were highly stable and were capable of maintaining catalytic activity for at least 12 h

Fabrication and photoelectrochemical studies of BiTiO pyrochlore thin films by aerosol assisted chemical vapour deposition

Phase pure thin film BiTiO photoelectrodes were produced by aerosol assisted chemical vapour deposition at 600 °C for the first time. X-ray diffraction analysis showed that the as-deposited BiTiO films were amorphous in nature; however, post-deposition annealing at 600°C for 12 h significantly increased the crystallinity to give phase pure BiTiO. Scanning electron microscopy revealed that the as-deposited film had a cauliflower-like structure with features ranging from 0.5 to 1.0 μm in size. It was found that the post-annealing step sintered the features together reducing the pores in the structure and giving rise to larger features of 1.0-2.0 μm in size. Optical studies showed that the BiTiO film had a direct band gap of 2.74 eV. The photoelectrochemical properties of BiTiO were tested and it was found that the electrodes exhibited a photocurrent density of 1.8 μA cm at 0.23 V vs. Ag|AgCl. Results showed that BiTiO is an attractive material for photoelectrochemical water splitting

Insights into mechanical compression and the enhancement in performance by Mg(OH)2 coating in flexible dye sensitized solar cells

The engineering of flexible dye sensitized solar cells (DSCs) by mechanical compression is one of the methods that allow low temperature processing of these devices. However, suppressing the high temperature sintering process also significantly reduces the performance of the cells. In our previous work [J. Phys. Chem. C, 116 (2012) 1211], we have attempted to improve flexible DSC performance by coating the porous TiO2 photoanode with an electrodeposited Mg(OH)2 layer. In that work, we have obtained one of the largest photovoltage reported to date in flexible DSCs (847 mV). In order to gain more insights into the reasons for both poorer performance of compressed cells and the origin of the voltage enhancement achieved by the Mg(OH)2 coating, here we present an in-depth study by means of electrochemical impedance spectroscopy, Mott-Schottky plots analysis and open-circuit voltage decays. The existence of a shunt resistance in the mechanically compressed cells is revealed, causing an additional drawback to the poor inter-particle necking. By introducing the Mg(OH)2 coating the recombination in the cell becomes significantly reduced, being the key reason which is responsible for the higher photovoltage. Additionally, the coating and the compression cause modifications in the surface states and in the nature of the interfaces with the electrolyte. This induces TiO2 conduction band displacements and shifts of the relative position of the modified states that influence the performance.This work was supported by UK EPSRC, DSTL, Johnson Matthey Plc and Department of Chemistry, Loughborough University. All members of the renewable energy r esearch group in the Department of Chemistry, Loughborough Univer sity are acknowledged for their assistance in this work. The authors would like to acknowledge previous related work conducted by S. Senthilarasu

Heterogeneous and homogenous catalysts for hydrogen generation by hydrolysis of aqueous sodium borohydride (NaBH4) solutions

It is clear that in order to satisfy global energy demands whilst maintaining sustainable levels of atmospheric greenhouse gases, alternative energy sources are required. Due to its high chemical energy density and the benign by-product of its combustion reactions, hydrogen is one of the most promising of these. However, methods of hydrogen storage such as gas compression or liquefaction are not suitable for portable or automotive applications due to their low hydrogen storage densities. Accordingly, much research activity has been focused on finding higher density hydrogen storage methods. One such method is to generate hydrogen via the hydrolysis of aqueous sodium borohydride (NaBH4) solutions, and this has been heavily studied since the turn of the century due to its high theoretical hydrogen storage capacity (10.8 wt%) and relatively safe operation in comparison to other chemical hydrides. This makes it very attractive for use as a hydrogen generator, in particular for portable applications. Major factors affecting the hydrolysis reaction of aqueous NaBH4 include the performance of the catalyst, reaction temperature, NaBH4 concentration, stabilizer concentration, and the volume of the reaction solution. Catalysts based on noble metals, in particular ruthenium (Ru) and platinum (Pt), have been shown to be particularly efficient at rapid generation of hydrogen from aqueous NaBH4 solutions. However, given the scarcity and expense of such metals, a transition metal-based catalyst would be a desirable alternative, and thus much work has been conducted using cobalt (Co) and nickel (Ni)-based materials to attempt to source a practical option. “Metal free” NaBH4 hydrolysis can also be achieved by the addition of aqueous acids such as hydrochloric acid (HCl) to solid NaBH4. This review summarizes the various catalysts which have been reported in the literature for the hydrolysis of NaBH4

Observations on the modified Wenker synthesis of aziridines and the development of a biphasic system

A cheap and reliable process for the modified Wenker cyclization to afford aziridines has been achieved using biphasic conditions for a range of amino alcohol starting materials. A 100 mmol “one-pot” process has also been devised and enantiopurity of the starting amino alcohol is retained in the aziridine product

Selective formation of trimethylene carbonate (TMC): atmospheric pressure carbon dioxide utilization

Carbon dioxide utilisation (CDU) is currently gaining increased interest due to the abundance of CO2 and its possible application as a C1 building block. We herein report the first example of atmospheric pressure carbon dioxide incorporation into oxetane to selectively form trimethylene carbonate (TMC), which is a significant challenge as TMC is thermodynamically less favoured than its corresponding co-polymer

Electrosynthesis of cyclic carbonates from epoxides and atmospheric pressure carbon dioxide

The use of CO2 for the preparation of value-added compounds has dramatically increased due to increased global warming concerns. We herein report an electrochemical cell containing a copper cathode and a magnesium anode that effectively converts epoxides and carbon dioxide to cyclic carbonates under mild electrochemical conditions at atmospheric pressure