2, Key Lab of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Northwest University, Xi' an, , China
3, University College London, London, , United Kingdom
The rapid recombination of electrons-holes and low visible-light utilization of TiO2 restrict the photocatalytic activity for hydrogen evolution.Various nano-carbon materials, serving as the charge transfer passway, are potential materials to overcome these obstacles. Very recently, 2D transition metal carbides (MXenes), are promising precursors for the synthesis of transition oxides/carbon hybrid materials. Firstly, we demonstrated a 2D-layered carbon/TiO2 (C/TiO2) architecture via CO2 oxidation of 2D-Ti3C2, in which the 2D carbon layers provide electron transport channels and improve the hole-electron separation efficiency. The 2D layered C/TiO2 delivers enhanced photocatalytic activity compared with pure TiO2 catalysts. Furthermore, we designed a novel laminated defect-controlled sulfur-doped TiO2 on carbon substrate (LDC-S-TiO2/C) hybrid catalyst to enhance the HER activity, shorten the diffusion path of electrons, and broaden the absorption wavelength. The novel synthesis method involves a sulfur impregnation process of Ti3C2 MXenes and the subsequent oxidation, which can simultaneously achieve the doping of TiO2 and the defect-engineering of carbon. The band-gap of LDC-S-TiO2/C is reduced to 1.62 eV, which means the synthesized materials can be excited from UV to visible lights. The synergistic effects of porous carbon and S-TiO2 result in a high photocatalytic H2 evolution rate of 333 μmol/g/h under visible light irradiation with a high apparent quantum yield (AQY) of 7.36% at 400 nm and it is also active even at 600 nm,, which is 48 times that of C/TiO2, and ≈1200 times that of TiO2. These stirring results shed a new insight in the supports and their defects for the photocatalytic activity, which can provide an alternative design strategy for achieving high active hybrid catalysts for clean energy conversion and utilization.