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

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 11; pp. 6591 - 6599
• Main Authors: Zheng, Jingxuan, Peng, Xiangfeng, Wang, Zhao
• Format: Journal Article
• Published: 25.03.2021
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d1cp00525a

Defect control is a promising way to enhance the electrocatalysis performance of metal oxides. Oxygen vacancy enriched NiCo 2 O 4 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 NiCo 2 O 4 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 NiCo 2 O 4 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 2 − % 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 NiCo 2 O 4 . 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. Plasma controls the oxygen vacancies and promotes N doping into NiCo 2 O 4 . CoO was also formed on the plasma samples, which is beneficial for fast charge transfer. The outstanding ORR activity is due to enhanced O adsorption and OH − desorption.