Sulfur-doping assisted defective CuCo₂O₄ as a bifunctional electrocatalyst for efficient water splitting

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy

Background:

• Electrocatalytic water splitting is a key technology for sustainable hydrogen production.
• Developing efficient bifunctional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for water splitting systems.
• Non-noble metal catalysts are highly sought after to reduce costs and improve scalability.

Purpose of the Study:

• To synthesize and characterize a novel sulfur-doped defective copper cobalt oxide (S-r-CCO) electrocatalyst.
• To evaluate the bifunctional electrocatalytic performance of S-r-CCO for both OER and HER.
• To investigate the synergistic effects of sulfur doping and oxygen vacancies on catalytic activity and stability.

Main Methods:

• Synthesis of S-r-CCO by doping sulfur ions into oxygen-defect-rich CuCo2O4.
• Electrochemical characterization including overpotential and Tafel slope measurements for OER and HER.
• Assembly of S-r-CCO||S-r-CCO electrodes in an anion exchange membrane (AEM) electrolyzer.
• Density functional theory (DFT) calculations to understand the electronic structure and catalytic mechanisms.

Main Results:

• S-r-CCO exhibited low overpotentials: 248 mV for OER and 113 mV for HER at 10 mA cm-2.
• Achieved Tafel slopes of 37.7 mV dec-1 (OER) and 76.5 mV dec-1 (HER), indicating efficient kinetics.
• The assembled S-r-CCO||S-r-CCO electrolyzer required only 1.78 V at 10 mA cm-2, outperforming commercial IrO2||Pt/Ti (1.93 V).
• DFT revealed that oxygen vacancies and Co(Cu)-S sites enhance electronic conductivity and catalytic activity.

Conclusions:

• The synergistic strategy of sulfur doping and oxygen vacancies in CuCo2O4 significantly enhances bifunctional electrocatalytic water splitting performance.
• S-r-CCO demonstrates excellent activity and stability, offering a promising non-noble metal alternative for efficient hydrogen production.
• This work provides a new avenue for designing advanced electrocatalysts for sustainable energy applications.