Strong phosphide-metaphosphate interaction in RuP/CoNiP₄O₁₂ for enhanced electrocatalytic water splitting

Strong metal-support interaction (SMSI) is a crucial concept in heterogeneous catalysis, which has been utilized to design efficient catalysts for electrocatalytic overall water splitting. Herein, a novel strong phosphide-metaphosphate interaction (SPmPI) is discovered in the RuP/CoNiP₄O₁₂ catalyst for the first time. The SPmPI leads to efficient electron transfer from RuP to CoNiP₄O₁₂ support, endowing the catalyst with a unique coordination environment of Ru-P and Ru-O, which is demonstrated to greatly facilitate the rate-determining water dissociation step. As a result, the RuP/CoNiP₄O₁₂ catalyst with proper Ru-P and Ru-O coordination numbers requires an ultralow overpotential of 27 mV to deliver a current density of 10 mA cm^-2 for hydrogen evolution reaction (HER) in alkaline media. Moreover, the catalyst inherits the remarkable catalytic activity from the CoNiP₄O₁₂ support for oxygen evolution reaction (OER), and therefore is also effective for overall water splitting (requiring 1.56 V to achieve 10 mA cm^-2 current density). This work not only reports a highly efficient catalyst for electrocatalytic overall water splitting, but also provides a novel concept of SPmPI for designing supported catalyst in heterogeneous catalysis.