Enhanced water electrolysis by construction and control of nickel (cobalt) phosphide/metal interface

Abstract

Using cobalt sulfate and nickel sulfate as main electrolytes, ammonium sulfate as an auxiliary electrolyte and buffer agent, and cheap iron pieces (FP) as the substrates, nickel and/or cobalt phosphide/metal heterogeneous catalytic electrode (M₂P/M/FP) was grown on the substrate in situ by electrodeposition followed by low temperature phosphating. M₂P/M/FP functioned as a good bifunctional electrode for HER and OER in 1 mol/L KOH, where Co₂P/Co/FP needed an overpotential of 52 and 288 mV, and (NC)₂P/(NC)/FP required that of 75 mV and 293 mV to afford 10 mA/cm². Previous similar studies often ignored the role of metal and only considered the water electrolysis catalysis of metal phosphide. In this research, it was clarified that for water electrolysis, the essence of high catalysis activity of the M₂P/M/FP electrode was the electronic interaction between metal and metal phosphide.