Type-II α-InS/InO 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 α-InS/InO nanowire heterostructures by a hydrothermally assisted sulfurization process. Structural characterization reveals that two distinct nanowire heterostructures: α-InS nanoparticles decorated InO nanowires and α-InS/InO core-shell nanowires were obtained by controlling the pH condition during the sulfurization process. Optical characterization results show α-InS/InO nanowire heterostructures exhibit a significantly decreased visible light emission and enhanced visible light absorption compared with the pure InO nanowires, revealing that an efficient photo-induced charge separation efficiency exists. The band offsets of the α-InS/InO 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 α-InS nanoparticles/InO nanowires exhibit significant photo-induced carrier lifetime improvement compare with the α-InS/InO 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 α-InS/InO nanowire heterostructures exhibited enhanced photocatalytic activities under visible light illumination, demonstrating their promising potentials in relevant photo-conversion applications.