Photocatalytic CO2 conversion to methanol by Cu2O/graphene/TNA heterostructure catalyst in a visible-light-driven dual-chamber reactor

Efficient photocatalytic CO2 conversion to methanol under visible light irradiation (X > 400 nm) was achieved in a light-driven dual-chamber reactor using the monolithic two-side Cu2O/graphene/TiO2 nanotube array (TNA) heterostructure as separated oxidation and reduction catalyst, that was prepared with anodic TNA as the substrate following by sequential electrochemical deposition of graphene and Cu2O. The combined heterojunction in the ternary composite helps to improve the photocatalytic performance by increasing light absorption, preventing electron-hole recombination and facilitating electron transfer across the heterojunction interfaces, as revealed by photoelectrochemical measurements. Methanol generation rate of 45 pmol cm(-2) h(-1) was achieved, which is much higher than those obtained for existing TNA-based photocatalysts reported. Moreover, the quantum efficiency of 5.71% at 420 nm has been attained. The improved photocatalytic activity together with the proposed reaction mechanism demonstrated the advantage of Cu2O/graphene/TNA heterostructure and effectiveness of the reaction system, which can efficiently suppress charge recombination, improve interfacial charge transfer and inhibit the backward reaction by separating the photocatalytic reaction sites. (C) 2016 Elsevier Ltd. All rights reserved.