Improving the Methane Oxidation by Self-Adaptive Optimization of Liquid-Metal Catalysts

Abstract

Methane (CH₄), a major greenhouse gas and abundant carbon resource, presents significant challenges in catalysis due to its high symmetry and thermodynamic stability, which tend to cause over-oxidation to CO₂. Traditional catalysts require high temperatures and pressures to facilitate CH₄ conversion, constrained by their rigid structures which lack the flexibility needed for optimizing complex reaction steps. This study introduces a novel Cu embedded liquid metal catalyst (Cu-LMC) based on gallium alloys, characterized by dynamic, self-adaptive structures that provide enhanced catalytic performance and selectivity. Our findings reveal that Cu-LMC achieves a high methane conversion to methanol yield (5.9 mol⋅g_Cu⁻¹⋅h⁻¹) with a selectivity of 82 %. The results show that mild surface oxidation significantly boosts the catalytic performance of Cu-LMC by increasing active copper sites through the formation of a Cu−O−Ga configuration while preserving the catalyst‘s structural flexibility. In situ X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Fine Structure (XAFS) analyses, along with ab initio Molecular Dynamics (AIMD) simulations, demonstrate that the Cu-LMC enables self-adaptive structural adjustments that lower methanol desorption energy and increase the energy barrier for by-product formation, optimizing the overall methane conversion process. The results underscore the importance of designing catalysts with dynamic and adaptable structures to overcome traditional limitations and improve efficiency in catalytic reactions.