Ni-doped TiO2 nanocubes wrapped by CNTs for synergic photocatalytic CH4 conversion

Direct conversion of CH4 to high valued chemicals under mild conditions is attractive but full of challenges. Here, we present a ternary composite that consists of Ni-doped TiO2 nanocubes (NCs) and CNTs as a new kind of catalyst (denoted as [email protected]2 NCs) for CH4 photocatalytic conversion to C1 oxygenated products at 30 °C. Using H2O2 as an oxidant, a high C1 oxygenated products yield and selectivity of 1.43 mol/(molNi·h) and 95.6% can be reached in 2 h at 30 °C. The superior photocatalytic performance resulted from the synergistic effects of TiO2 NCs, Ni species, and CNTs such as enhanced visible light absorption, improved electron/hole separation and charge transfer property, and lowered C-H bond cleavage energy required for CH4 activation, were carefully studied. Good reusability of the catalyst was studied by recycle experiments. Possible reaction mechanism based on the radical routes were carefully discussed by combining in-situ Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, radical scavenger experiments and density functional theory calculation.