Abstract
Metal-metal oxide (M-MO) interactions are important in catalysis. However, insights into how such interactions modulate lattice oxygen activity and stabilize critical reaction intermediates are scarce. In this work, using photocatalytic oxidative coupling of methane (POCM) as an example, we develop a simple and predictive model that defines M-MO interactions using two key factors: oxygen vacancy formation energy (E(OV)) and the methyl (*CH(3)) adsorption energy difference (ΔE(*CH(3))) across metal and oxide sites. Interfacial coupling comodulates E(OV) and ΔE(*CH(3)). E(OV) governs lattice-oxygen reactivity and the initial C-H activation, while ΔE(*CH(3)) controls CH(3) distribution between metal and oxide sites and thereby C-C coupling selectivity. Correlating E(OV) and ΔE(*CH(3)) with activity and selectivity reveals a unifying principle. Efficient methane conversion requires moderately labile lattice oxygen whereas selective C-C bond formation demands a large ΔE(*CH(3)) to drive methyl coupling for multicarbon products. Specifically, a AgPd/TiO(2) catalyst achieves an optimal balance in experimental testing, delivering over a methane conversion yield of 30 mmol g(-1) h(-1), a selectivity of 92% for C(2) products, and an operation stability of around 160 h. More broadly, the E(OV)-ΔE(*CH(3)) framework provides a predictive descriptor map for M-MO photocatalysts selection in POCM. This study fills a critical gap by establishing a quantitative framework for M-MO interactions, identifying interfacial synergy as the principal determinant of performance, and enabling rational M-MO catalyst design.