Efficient and stable bifunctional electrocatalysts Ni/NiᵪMᵧ (M = P, S) for overall water splitting

Abstract

Development of easy-to-make, highly active, and stable bifunctional electrocatalysts for water splitting is important for future renewable energy systems. Three-dimension (3D) porous Ni/Ni₈P₃ and Ni/Ni₉S₈ electrodes are prepared by sequential treatment of commercial Ni-foam with acid activation, followed by phosphorization or sulfurization. The resultant materials can act as self-supported bifunctional electrocatalytic electrodes for direct water splitting with excellent activity toward oxygen evolution reaction and hydrogen evolution reaction in alkaline media. Stable performance can be maintained for at least 24 h, illustrating their versatile and practical nature for clean energy generation. Furthermore, an advanced water electrolyzer through exploiting Ni/Ni₈P₃ as both anode and cathode is fabricated, which requires a cell voltage of 1.61 V to deliver a 10 mA cm⁻² water splitting current density in 1.0 M KOH solution. This performance is significantly better than that of the noble metal benchmark-integrated Ni/IrO₂ and Ni/Pt–C electrodes. Therefore, these bifunctional electrodes have significant potential for realistic large-scale production of hydrogen as a replacement clean fuel to polluting and limited fossil-fuels.