Transition Metal-Based Oxidation Catalysts to Mitigate Methane Emissions from Low-Concentration Sources

Methane is a greenhouse gas 28 times more potent than CO₂, with wetlands and agricultural practices accounting for 32 and 38% of total natural and anthropogenic methane emissions, respectively. The diluted and distributed nature of these emissions makes them hard to mitigate. Therefore, effective mitigation techniques are essential to reduce its impact, with catalytic oxidation emerging as a promising solution. In this study, methane oxidation over transition metal oxides is investigated to remove low-concentration CH₄ due to its high efficiency and low secondary pollution. The catalytic performance of different transition metal oxides (Co, Ni, and Mn), including single and binary metal oxides, was investigated under controlled conditions to facilitate direct comparison. The experimental investigation revealed that Co₃O₄-Mn _x O _y and Co₃O₄ catalysts achieved a 90% methane conversion rate at 330 and 380 °C. The high surface area and small crystallite size of Co₃O₄-Mn _x O _y increase the exposure of active sites, while the synergistic effect of Mn and Co promotes oxygen vacancy formation. In contrast, Co₃O₄ benefits from a high density of surface oxygen vacancies and an optimal acid-base balance, enabling intermediate stabilization and rapid redox cycling. By linking catalytic performance to structural features such as surface morphology, oxygen vacancies, acidity-basicity, and crystallite structures, this study provides insights into the reaction mechanisms governing methane oxidation.