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.