Electron transfer-driven low-temperature catalytic oxidation of low-concentration methane over Rh_x/CrO_y composite oxides

To mitigate environmental issues associated with low-concentration methane emissions (< 1%) from coal mine ventilation air methane. This study employed a one-pot sol–gel synthesis to prepare amorphous Rh/Cr oxide catalysts with varying Rh doping levels (0.05 to 0.5 wt%). The aim was to systematically investigate the correlation between Rh content, the catalysts' physicochemical properties, and their performance in methane oxidation. The Rh_0.3/CrO_y catalyst has been demonstrated to achieve a methane conversion rate as high as 90% at a reaction temperature of 448 °C. The results indicate that after calcination, a highly dispersed oxide structure Rh/CrO_y was formed, accompanied by the generation of a certain concentration oxygen vacancies. These vacancies provide structural support for electron transfer between the two metals. The Rh_0.3/CrO_y catalyst exhibited optimal catalytic activity at low temperatures. Characterization analysis reveals that the construction Rh-Cr bonds acting as charge transfer donors and acceptors, while modulation of oxygen vacancy concentration synergistically enhances the redox kinetics on the catalyst surface. However, high Rh loading (> 0.3 wt%) decreased activity due to particle aggregation.