Charge Self‐Regulation of Metallic Heterostructure Ni2P@Co9S8 for Alkaline Water Electrolysis with Ultralow Overpotential at Large Current Density

Abstract

Abstract Designing cost‐effective alkaline water‐splitting electrocatalysts is essential for large‐scale hydrogen production. However, nonprecious catalysts face challenges in achieving high activity and durability at a large current density. An effective strategy for designing high‐performance electrocatalysts is regulating the active electronic states near the Fermi‐level, which can improve the intrinsic activity and increase the number of active sites. As a proof‐of‐concept, it proposes a one‐step self‐assembly approach to fabricate a novel metallic heterostructure based on nickel phosphide and cobalt sulfide (Ni2P@Co9S8) composite. The charge transfer between active Ni sites of Ni2P and Co─Co bonds of Co9S8 efficiently enhances the active electronic states of Ni sites, and consequently, Ni2P@Co9S8 exhibits remarkably low overpotentials of 188 and 253 mV to reach the current density of 100 mA cm−2 for the hydrogen evolution reaction and oxygen evolution reaction, respectively. This leads to the Ni2P@Co9S8 incorporated water electrolyzer possessing an ultralow cell voltage of 1.66 V@100 mA cm−2 with ≈100% retention over 100 h, surpassing the commercial Pt/C║RuO2 catalyst (1.9 V@100 mA cm−2). This work provides a promising methodology to boost the activity of overall water splitting with ultralow overpotentials at large current density by shedding light on the charge self‐regulation of metallic heterostructure.

Keywords

• active electronic state
• bifunctional electrocatalyst
• heterostructure
• one‐step self‐assembly approach
• water splitting