Promoting surface lattice oxygen and oxygen vacancy of CeO2 for photothermal methane dry reforming over Ni/CeO2 catalysts

Abstract

The ever-increasing concentrations of CH4 and CO2 result in the greenhouse effect around the world. It’s meaningful to transform the gases for environment protection. In this work, we studied photothermal methane dry reforming over Ni/CeO2 catalysts by shaping CeO2 to nanorods and nanosheets, converting the greenhouse gases to syngas and trying to resolve challenges of Ni sintering and carbon deposition in the reaction. Through characterizations of physicochemical and optical properties, the surface lattice oxygen and oxygen vacancy were verified being more promoted on the nanorods catalysts than on the nanosheets catalysts, giving the greater reforming performance. The irradiation of visible-light accelerated CH4/CO2 rates, which was originated from that the photoelectrons reduced CO2 and the holes oxidized CHx. The oxygen vacancy strengthened metal-support interaction limiting Ni sintering, and the surface lattice oxygen gasified carbon precursors decreasing carbon deposition. The synergism between thermocatalysis and photocatalysis on the optimized 5Ni/CeO2 nanorod catalyst contributed to CH4 and CO2 rates up to 204 μmol/(gcats) and 245 μmol/(gcats), respectively, at 973 K, and carbon deposition less than 0.5 wt%. These were much superior to most reported performance. The work provided a novel photothermal approach for significantly decreasing carbon deposition in methane dry reforming.