Type-II α-In2S3/In2O3 nanowire heterostructures: evidence of enhanced photo-induced charge separation efficiency

Separation of photo-induced charges is crucial in controlling the performance of photocatalysts, photochemical cells, and photovoltaic devices. We developed a controlled synthesis of alpha-In2S3/In2O3 nanowire heterostructures by a hydrothermally assisted sulfurization process. Structural characterization reveals that two distinct nanowire heterostructures: alpha-In2S3 nanoparticles decorated In2O3 nanowires and alpha-In2S3/In2O3 core-shell nanowires were obtained by controlling the pH condition during the sulfurization process. Optical characterization results show alpha-In2S3/In2O3 nanowire heterostructures exhibit a significantly decreased visible light emission and enhanced visible light absorption compared with the pure In2O3 nanowires, revealing that an efficient photo-induced charge separation efficiency exists. The band offsets of the alpha-In2S3/In2O3 nanowire heterostructures were determined by X-ray photoemission spectroscopy and a type-II band alignment at the interface is confirmed. Time-resolved photoluminescence results reveal that the alpha-In2S3 nanoparticles/In2O3 nanowires exhibit significant photo-induced carrier lifetime improvement compare with the alpha-In2S3/In2O3 core-shell nanowire, due to a shorter charge carrier transport path, which ensures rapid charge separation at the interface. Because of the staggered band offset which promoted effective charge separation, the alpha-In2S3/In2O3 nanowire heterostructures exhibited enhanced photocatalytic activities under visible light illumination, demonstrating their promising potentials in relevant photo-conversion applications.