Defect Modulation of Z-Scheme TiO2/Cu2O Photocatalysts for Durable Water Splitting

Although possessing high activity for solar hydrogen production, exploring robust Cu2O-based photocatalysts remains a challenging task due to its intrinsic drawback of susceptible oxidation. Herein, we present a strategy to stabilize Cu2O by modulating the exposed facets and structural defects of TiO2. Both experimental characterizations and theoretical calculations proved that surface oxygen vacancies in 101-faceted TiO2 could create conducting channels for denoting electrons to Cu2O, mimicking the Z-scheme charge transfer in natural photosynthesis. Due to the defect-enhanced charge separation and the effective scavenging of oxidative holes in Cu2O, Cu2O/TiO2 heterostructures with exposed {101} facets and oxygen vacancies exhibited 251-fold increased activity for solar water splitting, together with unpredicted photostability. In contrast, defect-induced isolated states in the bulk of 001-faceted TiO2 led to the formation of Type II Cu2O/TiO2 junction with moderate photoactivity and poor stability. Thus, our work not only provides insights into the facet- and defect-dependent interfacial mechanism in heterostructured nanocatalysts but also opens up a promising avenue for developing high-performance noble-metal-free photocatalysts for energy conversion applications.