Two-dimensional restructuring of Cu2O can improve the performance of nanosized n-TiO2/p-Cu2O photoelectrodes under UV–Visible light

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.