Oxophilic Ce single atoms-triggered active sites reverse for superior alkaline hydrogen evolution

Abstract The state-of-the-art alkaline HER catalyst of united Ru single atoms and small Ru nanoparticles (Ru 1 -Ru n ) has sparked considerable research interest. However, it remains a serious problem that hydrogen evolution primarily occurs on the less active Ru single atoms instead of the more efficient small Ru nanoparticles in Ru 1 -Ru n , hence largely falling short of its full activity potential and unnecessarily increasing Ru usage amount. Here, we report that combining oxophilic Ce single atoms and fully-exposed Ru nanoclusters on a N functionalized carbon (Ce 1 -Ru n /NC) can facilely reverse alkaline hydrogen evolution centers to the more active fully-exposed Ru nanoclusters driven by the strong oxophilicity of Ce and thus greatly improves HER activity as well as Ru atom efficiency. Remarkably, the Ce 1 -Ru n /NC outperformed all the other Ru-based alkaline HER catalysts to date by its excellent mass activity. This finding is expected to shed new light on developing more efficient and cost-saving alkaline HER catalyst.