Enhanced methane partial oxidation via plasma–catalyst coupling using ion-exchanged copper geopolymers deposited on the inner electrode

This study investigates the partial oxidation of methane in a non-thermal plasma environment using an innovative plasma–catalysis reactor, where copper-based geopolymer materials are directly deposited onto the inner electrode. This original configuration enhances the plasma–catalyst interfacial contact, promoting efficient interaction between reactive plasma species and catalytic active sites. Two synthesis strategies were developed to tailor the nature and dispersion of copper species within the geopolymer matrix: (i) direct incorporation of CuO during geopolymer formation and (ii) post-synthesis copper ion exchange. While CuO incorporation exhibits limited influence on methane and oxygen conversions, product selectivity, and carbon balance, the ion-exchange approach significantly enhances catalytic performance. Methane conversion increases from 5.8% for CuO-incorporated samples (2 wt%) to 13.9% for ion-exchanged catalysts. Concurrently, CO selectivity improves from 39.7% to 55.5%, indicating a more efficient pathway toward syngas-oriented products. Notably, the energy requirement (ER) for CO production is markedly improved, decreasing from 14,603 kJ⋅mol⁻ 1 to 4,366 kJ⋅mol⁻ 1 . These results highlight the critical role of copper speciation and dispersion in plasma–catalytic systems. The superior performance of ion-exchanged copper geopolymers is attributed to enhanced accessibility of active sites and improved synergy with plasma-generated reactive species. This work demonstrates a promising and energy-efficient strategy for methane valorization through optimized plasma–catalyst coupling.