Interaction between InP and SnO2 on TiO2 nanotubes for photoelectrocatalytic reduction of CO2

Abstract In this work, InP and SnO2 were assembled on TiO2 nanotubes (NTs) using a hydrothermal method with a different order to obtain InP/SnO2/TiO2 NTs and SnO2/InP/TiO2 NTs. The energy band gaps of SnO2/InP/TiO2 NTs (2.96 eV) is lower than that of InP/SnO2/TiO2 NTs (3.15 eV), And the net current densities of SnO2/InP/TiO2 NTs (1.1 mA cm−2) is higher than that of InP/SnO2/TiO2 NTs (0.27 mA cm−2) in photoelectrocatalytic reduction of CO2 process at −1.4 V (vs SCE), indicating SnO2/InP/TiO2 NTs has a better photoelectrocatalytic property than InP/SnO2/TiO2 NTs. Photoelectric conversion efficiency of SnO2/InP/TiO2 NTs was 23.52%, which was 2.38 times larger than that of InP/SnO2/TiO2 NTs (9.88%). Methanol as the main product was yielded at 3.16 mmol L−1  cm−2 and 2.54 mmol L−1cm−2 after 6h photoelectrocatalytic process on SnO2/InP/TiO2 NTs and InP/SnO2/TiO2 NTs, respectively, indicating better photoelectrocatalytic property of SnO2/InP/TiO2 NTs than InP/SnO2/TiO2 NT, which was further explained by electron transfer mechanism.