Robust hydrogen evolution reaction activity catalyzed by ultrasmall Rh–Rh2P nanoparticles

Efficient electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline media are prominently important to advance the widespread application of industrial water splitting technology. In this work, we have synthesized ultrasmall rhodium–rhodium phosphide hetero-nanoparticles (3.4 nm, Rh–Rh2P@C) by partial phosphorization of Rh@C at 300 °C together with Na2HPO2. The constructed Rh–Rh2P@C requires only 24 mV and 37 mV overpotentials to reach 10 mA m−2 in 0.5 M H2SO4 and 1 M KOH electrolytes, which are lower than those of Rh@C and Rh2P@C due to the formation of heterointerfaces inducing modulation of local electronic structures and more active sites; as a result, a more moderate hydrogen adsorption–desorption strength is achieved for Rh–Rh2P@C as proved by theoretical calculation. Moreover, the calculated mass activity of Rh–Rh2P@C is 4 orders of magnitude higher than that of the benchmark Pt/C electrocatalyst. Besides, exceptional stability is recorded for Rh–Rh2P@C in both acidic and alkaline electrolytes due to the strong electronic interaction between Rh and Rh2P. This study offers a new strategy to manufacture efficient electrocatalysts for various applications.