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 CNTs-Ni@TiO2 NCs) for CH4 photocatalytic conversion to C1 oxygenated products at 30 degrees C. Using H2O2 as an oxidant, a high C1 oxygenated products yield and selectivity of 1.43 mol/(mol(N)(i).h) and 95.6% can be reached in 2 h at 30 degrees 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.

Automated summary

This study presents a method for the photocatalytic conversion of CH4 to C1 oxygenated products using a catalyst composed of CNTs-Ni@TiO2 NCs. The use of H2O2 as an oxidant allows for high yields and selectivity of C1 oxygenated products at 30 degrees C. The superior photocatalytic performance is attributed to the synergistic effects of TiO2 NCs, Ni species, and CNTs, including enhanced visible light absorption, improved electron/hole separation and charge transfer property, and lowered C-H bond cleavage energy required for CH4 activation.