Coordination Number-Dependent Complete Oxidation of Methane on NiO Catalysts

Parallel to the significance of catalysis by supported metal particles, transition-metal oxides (TMO) catalyze more than half of catalytic reactions. Exploration of the correlation between surface structures of TMOs and their corresponding catalytic performances is crucial for designing TMO catalysts with high activity and selectivity. Here we report that NiO nanocrystals with different exposed surface exhibit different catalytic performance on a probe reaction, CH4 complete oxidation. Both experimental findings and theoretical simulations suggest this difference in catalytic activity arises from the different coordination environment of Ni cations on a catalyst surface responsible for CH4 activation and complete oxidation. This coordination number-dependent catalysis demonstrates the significance of the coordination environment of cations of catalytic sites in understanding the catalytic performances of NiO catalysts at a molecular level. It suggests an avenue for developing TMO catalysts with high activity and selectivity through designing TMO catalyst surfaces consisting of cations in specific coordination environments or activating a TMO surface by introducing surface vacancies.