Nitrogen-Tuned Cationic Au Sites on TiO₂ Enable Selective Methane Oxidation to Methanol

Area of Science:

• Heterogeneous catalysis
• Materials science
• Chemical engineering

Background:

• Selective oxidation of methane to methanol is challenging due to methane's inert C-H bond and methanol's overoxidation susceptibility.
• Developing efficient catalysts for mild-condition methane conversion is crucial for sustainable chemical production.

Purpose of the Study:

• To design and synthesize a highly selective catalyst for methane to methanol oxidation.
• To investigate the role of nitrogen incorporation and gold nanoparticle characteristics in catalytic activity.
• To elucidate the reaction mechanism for selective methane oxidation.

Main Methods:

• Synthesis of nitrogen-incorporated TiO2-supported gold catalysts (Au/N-TiO2).
• Characterization using spectroscopic and structural analyses (e.g., DRIFTS).
• Catalytic performance evaluation in aqueous CH4/O2/CO media at 180 °C.
• Mechanistic studies including isotope labeling, kinetic analysis, and density functional theory (DFT) calculations.

Main Results:

• The optimized Au/N-TiO2 catalyst achieved a methanol productivity of 3956 μmol gcat−1 h−1 with 98% selectivity.
• Nitrogen incorporation modulated the electronic state of gold sites and optimized particle size for enhanced activity.
• DFT and experimental data revealed a CO-assisted, surface-mediated O2 activation pathway with surface methoxy intermediates.

Conclusions:

• Nitrogen incorporation in TiO2-supported gold catalysts is an effective strategy for selective methane oxidation.
• The study provides a mechanistic understanding of the CO-assisted catalytic pathway.
• The developed catalyst demonstrates superior performance compared to existing systems under similar conditions.