Efficient photothermal catalytic oxidation of methane over acid-activated α-MnO₂: Environmental implications and...

During oilfield production, large amounts of low-carbon alkanes are emitted, with methane predominant. To enhance methane oxidation under mild conditions, a photothermal synergistic system was developed using acid-activated α-MnO₂. Catalysts treated with HCl at varying concentrations were tested under different light intensities, methane levels, and space velocities. H_0.05-MnO₂ showed the best performance, achieving 90 % degradation at 342 °C under a gas hourly space velocity (GHSV) of 15,000 mL g^-1·h^-1, 30 °C lower than pristine α-MnO₂. Acid treatment optimized morphology and electronic structure, increasing Mn³⁺/(Mn³⁺+Mn⁴⁺) fraction from 14.3 % to 25.44 % and promoting reactive lattice oxygen. DFT calculations confirmed that acid activation reduced reaction barriers and facilitated charge redistribution. Under light, photogenerated carriers and Mn⁴⁺/Mn³⁺ redox cycling enhanced reactive oxygen species (ROS) generation, key to methane oxidation. This study links acid-induced structural/electronic tuning to enhanced photothermal catalysis, showing reduced energy demand for methane oxidation, offering guidance for low-energy low-carbon alkanes abatement in oilfields.