Ru single-atom catalyst anchored on sulfated zirconia for direct methane conversion to methanol

The direct CH4 conversion (DMC) to methanol is a challenging topic. In this study, the Ru/SZ (sulfated zirconia) single-atom catalysts (SACs) were synthesized and utilized to the DMC to methanol under mild conditions (70 °C). The yield over the Ru/SZ SACs (18.32 µmol, TOF ≥ 80 h–1) significantly exceeded the sum of the yields over the SZ (0.67 µmol) and Ru/ZrO2 (0.29 µmol), indicating that a new active center was formed on the Ru/SZ SACs. Combined with the results of the 13CH4 isotope labeling experiments and various characterizations including the pyridine adsorption infrared spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy, an unprecedented synergy effect between the single-atom and the super acid sites was pictured: The strong acidity of the Ru/SZ SACs could effectively promote the decomposition of H2O2 into the •OH, and the Ruδ+ (δ > 4) and the adjacent Zrγ+-•OH (γ > 4) could synergistically catalyze the CH4 to methanol.