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 (H2) and oxygen (O2) 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 H2 and O2 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 °C, the Ti3C2–TiO2 nanoflower shows a remarkable enhancement in the photocatalytic H2 and O2 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 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 H2 evolution and more holes participating in photooxidation for O2 evolution.