Abstract
p-Cu2O/n-TiO2 photoanodes were produced by electrodeposition of octahedral p-type Cu2O nanoparticles over n-type TiO2 nanotubes. The photoresponse of the composite p–n photoanodes was evaluated in photoelectrochemical cells operating at “zero-bias” conditions under either visible or UV–vis irradiation. In both operating conditions, the produced electrodes invariably followed the p–n-based photoanode operations but exhibited lower photoelectrochemical performance as compared to the bare n-TiO2 photoanode under UV–vis light. The reported experimental analysis evidenced that such decreased photoactivity is mainly induced by the scarce efficiency of the nanosized p–n interfaces upon irradiation. To overcome such limitation, a restructuring of the originally electrodeposited p-Cu2O was promoted, following a photoelectrochemical post-treatment strategy. p-Cu2O, restructured in a 2D leaf-like morphology, allowed reaching an improved photoelectrochemical performance for the p–n-based photoanode under UV–vis light. As compared to the bare n-TiO2 behavior, such improvement consisted of photoanodic currents up to three times larger. An analysis of the mechanisms driving the transition from compact (∼100 nm) octahedral p-Cu2O to wider (∼1 μm) 2D leaf-like structures was performed, which highlighted the pivotal role played by the irradiated n-TiO2 NTs.
Highlights
Over the past two decades, increasing energy demand accompanied by the need to decrease both carbon dioxide emissions and the dependence on fossil fuels[1] has accelerated the development and optimization of technologies useful to generate electric energy from renewable sources, including solar, wind, and geothermal.[2]
The performance of the composite TiO2/Cu2O electrodes increases with increasing Cu2O content up to a maximum and eventually decreases when the Cu2O content is doubled,[44] suggesting that the Cu2O size influences the overall composite electrode performance, even upon direct bias application. This result is in agreement with our previous findings, where we reported that the photocatalytic activity of the composite TiO2/Cu2O in the absence of bias progressively deteriorates at increasing Cu2O loading,[45] which corresponds to an increase in the sizes of the electrodeposited Cu2O.46
By testing the synthesized photoanodes in PEC cells operating at zero-bias conditions, it was demonstrated that the p−n photoelectrodes can effectively work as photoanodes under both UV−vis and visible-only irradiation
Summary
ABSTRACT: p-Cu2O/n-TiO2 photoanodes were produced by electrodeposition of octahedral p-type Cu2O nanoparticles over n-type TiO2 nanotubes. The photoresponse of the composite p−n photoanodes was evaluated in photoelectrochemical cells operating at “zero-bias” conditions under either visible or UV−vis irradiation. In both operating conditions, the produced electrodes invariably followed the p−n-based photoanode operations but exhibited lower photoelectrochemical performance as compared to the bare n-TiO2 photoanode under UV−vis light. The reported experimental analysis evidenced that such decreased photoactivity is mainly induced by the scarce efficiency of the nanosized p−n interfaces upon irradiation. To overcome such limitation, a restructuring of the originally electrodeposited p-Cu2O was promoted, following a photoelectrochemical post-treatment strategy.
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