Polyoxometalate derived bimetallic phosphide electrocatalysts for high-efficiency hydrogen evolution reaction

Abstract

Transition metal phosphides (TMPs) have gradually developed as star catalysts in the field of electrocatalytic hydrogen evolution. In this work, a honeycomb porous bimetallic phosphide embedded in a N,P-dual-doped carbon composite (abbr.: MoP/MoNiP@NPC-800) was prepared by one-step high-temperature pyrolysis of polyoxometalate (POM) [Ni(2,2′-bipy)₃][Mo₆O₁₉] (abbr.: Ni-POM) assisted by NaH₂PO₂·H₂O. The catalyst MoP/MoNiP@NPC-800 exhibits surprising HER activity, by delivering low overpotentials of 50.4/72.6 mV at 10 mA cm⁻², small Tafel slopes of 54/74 mV dec⁻¹, and reliable ∼120 hours stability at 50 mA cm⁻², respectively, in 1.0 M KOH and 0.5 M H₂SO₄. The excellent HER catalytic activity is attributed to the synergistic effect of ample MoP and MoNiP dual active sites, which result from the N,P-dual-doped carbon layer protecting MoP and MoNiP from agglomeration and corrosion, and the 3D honeycomb porous structure increasing the number of exposed active sites and facilitating mass transfer. Theoretical calculations further prove that the most active sites for the HER are the P sites of the MoP and MoNiP dual-active centers. This study provides an effective strategy for the synthesis of bimetallic phosphides using POMs as sacrificial templates.