Phosphatizing engineering of heterostructured Rh2P/Rh nanoparticles on doped graphene for efficient hydrogen evolution in alkaline and acidic media

Abstract

A wide diversity of phosphides of platinum-group metal including Rh, Ru and Ir exhibit intriguing electrocatalytic activity toward hydrogen evolution reaction (HER). The phosphidation degree, namely the P dosage in these phosphides shows pronounced influence on the catalytic performance but is hard to control. In this work we developed a reliable strategy to synthesize Rh2P-based nanoparticles with controlled phosphidation degree, and investigated the influence of phosphidation degree on HER. It is found that the heterostructured Rh2P/Rh nanoparticle, i.e., the P-deficient composite with mixed metallic and phosphide phases, outperforms either the metallic Rh or pure Rh2P nanoparticles. As-synthesized Rh2P/Rh nanoparticles supported on P/N co-doped graphene (denoted as Rh2P/Rh-G) display remarkable HER activity with tiny overpotential of 17 and 19 mV at 10 mA cm−2 current density in alkaline and acid, efficiently surpassing its Rh-based rivals and benchmark Pt/C catalyst. Meanwhile it illustrates a large mass-specific activity (3.23 and 6.26 A mg−1 @50 mV overpotential in alkaline and acid, respectively) due to its high activity and low metal loading. Density functional theory (DFT) calculation indicates that the Rh2P/Rh heterostructured interface possesses the optimal close-to-zero value of hydrogen adsorption energy and water dissociation process is accelerated, and thus boosts HER activity.