Abstract
Hydrogen and hydrogen peroxide have been photoelectrocatalytically produced by electrocatalytic reduction using simple carbon electrodes made by depositing a mesoporous carbon film on carbon cloth. Visible-light-absorbing photoanodes have been constructed by depositing mesoporous CdS/TiO2 or WO3 films on transparent fluorine-doped tin oxide (FTO) electrodes. Both produced substantial photocurrents of up to 50 mA in the case of CdS/TiO2 and 25 mA in the case of WO3 photoanodes, and resulting in the production of substantial quantities of H2 gas or aqueous H2O2. Maximum hydrogen production rate was 7.8 µmol/min, and maximum hydrogen peroxide production rate was equivalent, i.e., 7.5 µmol/min. The same reactor was employed for the production of both solar fuels, with the difference being that hydrogen was produced under anaerobic and hydrogen peroxide under aerated conditions. The present data promote the photoelectrochemical production of solar fuels by using simple inexpensive materials for the synthesis of catalysts and the construction of electrodes.
Highlights
Hydrogen and hydrogen peroxide are two very important fuels
The most realistic route for energy production using H2 O2 as fuel is via hydrogen peroxide fuel cells
In the first 30 min, the quantity of dissolved hydrogen peroxide was found to be equal to 7.6 mg/L. This corresponds to an average of 7.5 μmol/min, and for a current of 25 mA, it corresponds to a Faradaic efficiency of 96%. These numbers are subject to substantial error; they do show that photoelectrocatalysis is a very efficient method for hydrogen peroxide production, using simple carbon black as an electrocatalyst
Summary
Hydrogen and hydrogen peroxide are two very important fuels. Hydrogen offers the highest gravimetric heat of combustion, ~286 kJ/mol (143 MJ/kg), and it is the most benign of all standard fuels, since its combustion produces water. Holes are consumed for the oxidation of the fuel [8], while the electrons flow through an external circuit to the cathode electrode, where they assist reduction reactions. Hydrogen may be produced under anaerobic conditions and hydrogen peroxide in the presence of oxygen Both may be produced at the cathode electrode, provided that an electric current flows in an external circuit that connects the two electrodes. An organic fuel is consumed by photocatalytic oxidation at the anode electrode, providing electrons that drive the production of hydrogen or hydrogen peroxide at the cathode electrode. This process is schematically represented by Figure 1. Ethanol is oxidized at the photoanode, while peroxide is produced by the reduction oxygen at the cathode. System that may be used to produce solar fuels by the conversion of solar radiation and the
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