Building surface defects by doping with transition metal on ultrafine TiO2 to enhance the photocatalytic H2 production activity

Abstract

Inefficient charge separation and limited light absorption are two critical issues associated with high-efficiency photocatalytic H2 production using TiO2. Surface defects within a certain concentration range in photocatalyst materials are beneficial for photocatalytic activity. In this study, surface defects (oxygen vacancies and metal cation replacement defects) were induced with a facile and effective approach by surface doping with low-cost transition metals (Co, Ni, Cu, and Mn) on ultrafine TiO2. The obtained surface-defective TiO2 exhibited a 3–4-fold improved activity compared to that of the original ultrafine TiO2. In addition, a H2 production rate of 3.4 μmol/h was obtained using visible light (λ > 420 nm) irradiation. The apparent quantum yield (AQY) at 365 nm reached 36.9% over TiO2-Cu, significantly more than the commercial P25 TiO2. The enhancement of photocatalytic H2 production activity can be attributed to improved rapid charge separation efficiency and expanded light absorption window. This hydrothermal treatment with transition metal was proven to be a very facile and effective method for obtaining surface defects.