Collaborative multi-interface engineering and dynamic iron exchange boost robust bifunctional water electrolysis at 2 A cm−2†

Abstract

Due to the incompatibility and inconsistency of the active species for hydrogen and oxygen evolution reactions, nearly all the intermetallic catalysts present superb catalytic activity for one half reaction at the expense of another reaction activity, thus leading to large electric power consumption of alkaline water splitting. To achieve low-voltage electrochemical H₂ production through water electrolysis, here we present a hierarchical trimetal hybrid catalyst comprising intermetallic nickel–molybdenum alloy (MoNi₄) particles and metallic iron particles anchoring on MoO₂ nanorod arrays with synergistic multimetal sites that exhibit relay catalysis for bifunctional water splitting as rationalized by operando Raman, X-ray photoelectron spectroscopic studies and density functional theory (DFT) calculations. These metal sites situated at the multilevel interfaces of Fe/MoNi₄/MoO₂ collaboratively promote the reaction pathway including initial water adsorption/dissociation, hydrogen adsorption and oxygen-containing intermediate adsorption, thereby substantially jeopardizing overall water splitting at 500/1000 mA cm⁻² with a record low cell voltage of around 1.6 V, which is exceptionally better than that of noble IrO₂⁽⁺⁾||Pt/C⁽⁻⁾ couple electrodes (>1.9 V). This intermetallic catalyst demands extremely low overpotentials of 59 and 277 mV for hydrogen and oxygen evolution reactions at 500 mA cm⁻², outperforming nearly all the inexpensive bifunctional electrocatalysts. Especially, this catalyst can exhibit superior catalytic performance at an industrial-level current density of 500–2000 mA cm⁻² without noticeable degradation. This work paves a promising avenue to develop efficient bifunctional non-noble catalysts for industrial-level water electrolysis via relay catalysis.