Decoupling fast hydrogen oxidation reaction on a tandem electrocatalyst.

The hydrogen oxidation reaction (HOR) shows fast kinetics in proton exchange membrane fuel cells (PEMFCs), and has not drawn intense attention. Here, we propose a tandem electrocatalysis concept, decoupling HOR on two independent active sites for accelerated kinetics. As a proof-of-concept application, a Ru-based tandem HOR catalyst is designed, with Ru nanoclusters decorated with Pt single atoms. Experimental and theoretical studies suggest that H dissociation occurs at Ru sites, and then the produced H species migrate to Pt sites followed by the desorption of H. The strong Ru-H interaction promotes the H dissociation step, while the optimum Pt-H interaction ensures the fast desorption, thereby substantially enhancing the HOR kinetics. In H-O fuel cells, this catalyst enables a peak power density of 1.91 W cm and a high anodic mass activity of 23.12 A mg at 0.9 V with an ultralow noble metal loading of 5 μg cm. This work advances the development of low-cost anode catalysts for fuel cells and provides more insight into understanding hydrogen electrocatalysis.