Hydroxyl‐Promoted C─C Coupling for Selective Methane Conversion into Ethane on Cerium Oxide Photocatalyst

Converting methane into high-value chemicals under mild conditions offers substantial environmental and energy benefits but is challenged by the difficulty of activating C─H bonds and preventing over-oxidation. In this study, the pivotal role of hydroxyl-rich surfaces on noble-metal-free photocatalysts is demonstrated in directing selective C─C coupling of methane. These surface hydroxyls not only enhance methane chemisorption and improve charge separation, but also promote favorable interactions with molecular oxygen, collectively boosting catalytic performance. Furthermore, the hydroxyl groups lower the energy barrier for ethane formation while suppressing its over-oxidation to CO₂, resulting in significantly improved selectivity. Under ambient conditions in a flow-reactor system, the catalyst achieves a continuous ethane production rate of 187 µmol·g^-1·h^-1 with approximately 97% selectivity over an extended operation period (>200 h), surpassing previous noble-metal-free photocatalytic systems. This work provides critical insights into the role of hydroxyl-modified local environment in methane valorization, paving the way for the development of sustainable and efficient catalytic systems.