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

Defect control is a promising way to enhance the electrocatalysis performance of metal oxides. Oxygen vacancy enriched NiCoO 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 NiCoO 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 NiCoO 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 HO % was as low as 0.59% and current density was 4.9 mA cm at 0.2 V (Vs. RHE) on the plasma-treated NiCoO. 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.