Plasma-assisted defect engineering of N-doped NiCo2O4 for efficient oxygen reduction

Defect control is a promising way to enhance the electrocatalysis performance of metal oxides. Oxygen vacancy enriched NiCo2O4 was successfully prepared using cold plasma. Oxygen as a plasma-forming gas introduces oxygen vacancies via electron etching. The concentration of oxygen vacancies can be controlled by different plasma-forming gas. CoO, which formed on the plasma samples, is beneficial for quick charge transfer and electrocatalytic performance. A high amount of nitrogen atoms of up to 10.1% was doped on NiCo2O4 because of the enriched oxygen vacancies and improved the stability of the oxygen defects and the conductivity of the catalyst. Electrocatalytic studies showed that the plasma-induced N-doped NiCo2O4 shows enhanced electrocatalytic performance for the oxygen reduction reaction (ORR). It shows a typical four-electron process that considerably improves the current density and onset potential. The HO2- % was as low as 0.59% and current density was 4.9 mA cm(-2) at 0.2 V (Vs. RHE) on the plasma-treated NiCo2O4. Calculations based on density functional theory reveal the mechanism for the promotion of the catalytic ORR activity via plasma treatment. This increases the electron density near the Fermi level, reducing the work function, and changing the position of the d-band center.

Automated summary

Defect control using cold plasma to enhance electrocatalytic performance of metal oxides has been proven successful. Introducing oxygen vacancies through plasma treatment with different plasma-forming gases can improve charge transfer and electrocatalytic performance. Plasma-induced N-doping in NiCo2O4 shows enhanced electrocatalytic performance for oxygen reduction reaction, with improvements in current density and onset potential.