Oxidative contaminant degradation on bimetallic boride electrocatalysts enhances anodic charge transfer for efficient H2 production

Abstract

Hydrogen evolution reaction (HER) via electrocatalytic water splitting is restricted by the sluggish oxygen evolution reaction (OER). By contrast, alkaline urea electrolysis provides the prospect of energy-saving H2 production together with urea-rich wastewater purification. Here, we report a feasible and reliable strategy for the fabrication of the cuboid-like Co2MoB4 electrode anchored on Co foam. The Co2MoB4 electrocatalyst exhibits high activity toward HER and urea oxidation reaction (UOR) as well as superior durability. Specifically, a low HER overpotential of 230 mV is required to support a current density of 100 mA/cm2, and an alkaline urea electrolyzer can achieve 50 mA/cm2 at voltage of 1.632 V, lower than that in alkaline or acetamide electrolytes. In situ electrochemical characterizations reveal that the desired oxidation state of the CoIII formed on the surface is the key features determining a high reactivity for urea oxidation with shortening the oxidation pathway. This scenario is beneficial for accelerating charge transfer across the interface between the anode and electrolyte. Differently, the higher valence Co (IV) is generated to further oxidizing the acetamide, similar to the OER process. Our work demonstrates the promising development of bimetallic borides for urea splitting to produce H2 with reduced energy consumption.