Coverage-Dependent Selective Conversion of Methane into Value-Added Ethane over Noble-Metal-Free Ni₁-CeO₂ Photocatalyst

Direct methane conversion to value-added chemicals under mild conditions presents a promising route toward net-zero carbon emissions. However, this process encounters significant challenges in efficiently activating inert C-H bonds and preventing excessive oxidation to CO₂. Herein, we propose a coverage-dependent strategy that leverages the correlation between methane coverage and C-C coupling selectivity, thereby enhancing both the activity and selectivity. By tuning the Lewis acidity of a well-defined atomic 3d transition metal-modified ceria, from weak to moderate, it boosts methane adsorption capacity and promotes its dissociative activation. Additionally, incorporating a nickel cocatalyst improves the charge separation through efficient hole extraction. The optimal noble-metal-free catalyst (Ni₁-CeO₂) delivers exceptional room-temperature performance, achieving a production rate of 243 μmol·g^-1·h^-1 with approximately 90% ethane selectivity over an ultralong test (>350 h), outperforming previously reported noble-metal-free catalysts. This work provides new insights into selectivity regulation via optimization of chemisorbed methane coverage and paves the way for the design of advanced noble-metal-free catalysts.