0D/2D Co3O4/Ti3C2 MXene Composite: A Dual-Functional Electrocatalyst for Energy-Saving Hydrogen Production and Urea Oxidation

Abstract

Electrocatalytic water splitting to produce hydrogen (H2) is a sustainable way of meeting energy demands at no environmental cost. However, the sluggish anodic reaction imposes a considerable overpotential requirement. By contrast, the electrocatalytic urea oxidation reaction offers the prospect of energy-saving H2 production together with urea-rich wastewater purification. In this work, a 0D/2D Co3O4/Ti3C2 MXene composite was synthesized by a simple solution reaction approach under mild conditions and applied as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) in basic medium (1 M KOH+0.5 M urea). The Co3O4/Ti3C2 MXene electrodes delivered a current density of 10 mA cm–2 at an overpotential of 124 mV for HER and required 1.40 V to reach 10 mA cm–2 for UOR. The hybrid catalyst could maintain high activity after 40 h continuous catalytic reaction for both UOR and HER. Its catalytic performance was significantly improved compared to that of pure Ti3C2 MXene and Co3O4 solving the problem of insufficient exposure of active sites caused by too large particle size and agglomeration of Co3O4 particles. Notably, Co3O4/Ti3C2 MXene was applied as a bifunctional catalyst for overall urea-containing water splitting, and showed certain energy saving advantages compared with other reported Co-based catalysts. This work provides a strategy for application other than noble metal-based electrode materials for urea-containing wastewater purification coupled with H2 production.