Tailoring Interfacial Charge Transfer of Epitaxially Grown Ir Clusters for Boosting Hydrogen Oxidation Reaction

The sluggish kinetics of hydrogen oxidation reaction (HOR) is one of the critical challenges for anion exchange membrane fuel cells. Here, we report epitaxial growth of Ir nanoclusters (<2 nm) on a MoS2 surface (Ir/MoS2) and optimize the alkaline HOR activity via tailoring interfacial charge transfer between Ir clusters and MoS2. The electron transfer from MoS2 to Ir clusters can effectively prevent the oxidation of Ir clusters, which is not the case for carbon-supported Ir nanoclusters (Ir/C) synthesized using the same method. Moreover, the HOR performance of the Ir/MoS2 can be further optimized by tuning the hydrogen binding energy (HBE) via a precise annealing treatment. A substantial exchange current density of 1.28 mA cm(ECSA)(-2) is achieved in the alkaline medium, which is similar to 10 times over that of Ir/C. The HOR mass-specific activity of Ir/MoS2 heterostructure is as high as 182 mA mg(Ir)(-1). The experimental results and density functional theory calculations reveal that the significant improved HOR activity is attributed to the decreased HBE, which highlights epitaxial growth is an effective way for boosting catalytic activity of heterostructured catalysts.