Lattice Oxygen in Photocatalytic Gas–Solid Reactions: Participator vs. Dominator

Lattice‐oxygen activation has emerged as a popular strategy for optimizing the performance and selectivity of oxide‐based thermocatalysis and electrolysis. However, the significance of lattice oxygen in oxide photocatalysts has been ignored, particularly in gas–solid reactions. Here, using methane oxidation over a Ru 1 @ZnO single‐atom photocatalyst as the prototypical reaction and via 18 O isotope labelling techniques, we found that lattice oxygen can directly participate in gas–solid reactions. Lattice oxygen played a dominant role in the photocatalytic reaction, as determined by estimating the kinetic constants in the initial stage. Furthermore, we discovered that dynamic diffusion between O 2 and lattice oxygen proceeded even in the absence of targeted reactants. Finally, single‐atom Ru can facilitate the activation of adsorbed O 2 and the subsequent regeneration of consumed lattice oxygen, thus ensuring high catalyst activity and stability. The results provide guidance for next‐generation oxide photocatalysts with improved activities and selectivities.