Electron Delocalization in Ni-Co Active Pairs for Efficient and Robust Urea Electrooxidation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nickel hydroxide (Ni(OH)₂) shows promise as a urea oxidation reaction (UOR) catalyst.
• Performance is limited by electron localization in Ni^II, hindering the formation of active Ni^III species.
• Developing efficient catalysts is crucial for sustainable energy applications like hydrogen production.

Purpose of the Study:

• To overcome the limitations of Ni(OH)₂ in UOR catalysis.
• To enhance the Ni^II/Ni^III transformation and improve catalytic activity and stability.
• To explore the potential of Co-doped Ni(OH)₂ integrated with CoNi alloy for energy-saving hydrogen production.

Main Methods:

• Construction of electron-delocalized Ni-Co active pairs (Ni^II+δ-O-Co^II+δ) via Co doping of Ni(OH)₂.
• Integration of doped Ni(OH)₂ with a CoNi alloy.
• Electrochemical characterization to evaluate UOR performance and stability.

Main Results:

• Achieved an ultralow UOR potential of 1.288 V_RHE at 10 mA cm^-2, outperforming undoped and other Ni-Co configurations.
• Demonstrated enhanced N-terminal urea adsorption and weakened N─H bonds due to upshifted d-band centers.
• Exhibited record stability for 2100 hours across a wide current density range (10-500 mA cm^-2).

Conclusions:

• Electron-delocalized Ni-Co active pairs effectively accelerate the Ni^II/Ni^III transformation for UOR.
• The catalyst design significantly reduces the energy barrier of the rate-determining step in UOR.
• The developed catalyst offers a dual-purpose solution for energy-saving hydrogen production from urea/urine and environmental remediation.