Facet-Selective hydrogen evolution on Rh2P electrocatalysts in pH-Universal media

Surface atomic structures of transition metal phosphides determine the electrocatalytic activities toward hydrogen evolution reaction (HER). In this work, we developed a new facet-guided phosphorization strategy to synthesize Rh 2 P electrocatalysts with tunable facet exposure and further unveil their intrinsic facet-dependent HER activity in pH-universal media. The Rh 2 P nanoparticles feature {1   1   1} and {2   0   0} facets when the precursors of Rh nanoctahedron and nanocube are used, respectively. The Rh 2 P{2   0   0} catalyst showed a remarkable HER performance with the overpotential of 23, 22 and 54 mV at a current density of 10 mA cm −2 in 1.0 M KOH, 0.5 M H 2 SO 4 and 1.0 M phosphate buffer, respectively. The mass activity and specific activity of Rh 2 P{2   0   0} were 3～5-times higher than those of Rh 2 P{1   1   1} and Pt/C catalysts. As elucidated using theoretical calculations, the overlapping of Rh-4d and P-3p of Rh 2 P{2   0   0} and Rh 2 P{1   1   1} results in distinct electronic states of surface Rh atoms, leading to varied free energies for water dissociation and hydrogen adsorption/desorption.