Ti3C2 MXene-derived Ti3C2/TiO2 nanoflowers for noble-metal-free photocatalytic overall water splitting

Photocatalytic overall water splitting is an environmentally friendly technique for hydrogen (H-2) and oxygen (O-2) production. Here, we report an in situ growth strategy for synthesizing Ti3C2-TiO2 nanoflowers by simultaneous oxidation and alkalization, followed by ion exchange and calcination processes of Ti3C2 MXene as photocatalysts for H-2 and O-2 evolution from water splitting. The effect of the calcination temperature on the photocatalytic performance of the obtained Ti3C2-TiO2 nanoflowers is elucidated. With an optimized calcination temperature of 500 degrees C, the Ti3C2-TiO2 nanoflower shows a remarkable enhancement in the photocatalytic H-2 and O-2 evolution reaction compared with that of pure TiO2. Upon further removing the sacrificial reagent, overall water splitting is accomplished with the Ti3C2-TiO2 nanoflowers (without the use of any noble metal). We further show that the Ti3C2-TiO2 nanoflower has high stability and good reproducibility. The superior performance originated from the 3D porous nanoflower-like structure, which provides more reactive sites, a greater ability to reflect and scatter light, and reduce the diffusion length of photogenerated holes and electrons. Moreover, intimate contact between Ti3C2-TiO2 MXene and TiO2 generates synergetic effect and Schottky junction, enhancing the charge separation and effectively inhibiting recombination, leading to more electrons participating in photoreduction for H-2 evolution and more holes participating in photooxidation for O-2 evolution. (C) 2018 Elsevier Ltd. All rights reserved.