Efficient and Highly Selective Urea Electrooxidation via Cu Incorporation in Tetrahedral Sites of Spinel Co3O4 Nanowires for Enhanced Hydrogen Production

Abstract

The electrochemical urea oxidation reaction (UOR) is regarded as a green and promising technology to cope with the high-energy consumption of hydrogen production and environmental issues. However, the sluggish kinetics and by-product oxynitride production pose critical challenges for its widespread application. Herein, by introducing a heteroatom Cu into the tetrahedral Co sites in spinel Co3O4, the accordingly altered electronic state of Co enables significantly improved activity for the UOR. Operando experiments and theoretical calculations indicate that the occupation of Cu2+(Td) sites facilitates the dehydrogenation process and favors the UOR toward the “carbonate” pathway. Notably, Cu-doped Co3O4 achieves 10 mA cm−2 for the UOR under an applied potential of 1.32 V, 210 mV lower than the pristine Co3O4. Integrating into a membrane electrode assembly flow electrolyzer as the anode, a voltage input of 2.04 V can deliver the current density of 1 A cm−2. This work provides valuable insights to develop a high-performance UOR electrocatalyst for steering energy-saving hydrogen production enabled by a more environmentally friendly “carbonate” pathway.