A Monodisperse Rh2P‐Based Electrocatalyst for Highly Efficient and pH‐Universal Hydrogen Evolution Reaction

The search for Pt‐free electrocatalysts exceeding pH‐universal hydrogen evolution reaction (HER) activities when compared to the state‐of‐the‐art commercial Pt/C is highly desirable for the development of renewable energy conversion systems but still remains a huge challenge. Here a colloidal synthesis of monodisperse Rh2P nanoparticles with an average size of 2.8 nm and their superior catalytic activities for pH‐universal HER are reported. Significantly, the Rh2P catalyst displays remarkable HER performance with overpotentials of 14, 30, and 38 mV to achieve 10 mA cm−2 in 0.5 m H2SO4, 1.0 m KOH, and 1.0 m phosphate‐buffered saline, respectively, exceeding almost all the documented electrocatalysts, including the commercial 20 wt% Pt/C. Density functional theory calculations reveal that the introduction of P into Rh can weaken the H adsorption strength of Rh2P to nearly zero, beneficial for boosting HER performance. 2.8 nm monodisperse Rh2P nanoparticles with narrow size distribution are synthesized through a one‐pot hot solution colloidal synthetic route and further used as remarkable catalysts for pH‐universal hydrogen evolution reaction (HER). The enhanced HER performance is attributed to the introduction of P into Rh, which resulting in the optimized free energy of hydrogen adsorption.