Visible light-sensitive mesoporous N-doped Ta2O5 spheres: synthesis and photocatalytic activity for hydrogen evolution and CO2 reduction

Abstract

Crystallized mesoporous tantalum pentoxide spheres (CMTS) with particle diameters of ca. 100–500 nm and composed of Ta2O5 nanocrystals were synthesized for the first time by a combination of the sol–gel process and heat-treatment with the aid of carbon reinforcement. The specific surface area of the CMTS was up to 105 m2 g−1 and the pore diameter was controllable in the range of 5.6–17 nm by changing the crystallization temperature. Visible light-sensitive p-type N-doped Ta2O5 (N-CMTS) containing 5 at% N was successfully obtained by treatment of CMTS with ammonia, while retaining the mesoporosity and morphology of CMTS. N-CMTS exhibited excellent photocatalytic activity for hydrogen evolution and CO2 reduction (with ruthenium-complex) under visible light irradiation (≥410 nm) due to their larger surface area and controlled morphology compared with previously reported N-doped Ta2O5 fine particles.