Amorphous carbon having higher catalytic activity toward oxygen reduction reaction: Quinone and carboxy groups introduced onto its surface

• Published in: Diamond and related materials 2020-08, Vol.107, p.107900, Article 107900
• Main Authors: Honda, Kensuke, Waki, Yuta, Matsumoto, Akari, Kondo, Bunta, Shimai, Yohsuke
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Carbon; Catalysts; Catalytic activity; Corrosion resistance; Hydrogen peroxide; Oxygen reduction reactions; Quinones
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2020.107900

Amorphous carbon (a-C) based catalysts having higher activity and stability for oxygen reduction reaction (ORR) were achieved by introducing quinone and carboxy groups onto a-C surfaces. The surface-bonded quinone groups increased the rate of ORR to hydrogen peroxide. The surface carboxy groups promoted the activity toward electrochemical peroxide reduction. However, few studies have reported on their contribution. ORR activity was controlled by varying density of quinone and carboxy groups on the a-C surfaces. The ORR activity was proceeded by 2 + 2 electron mechanism through H2O2 that acted as an intermediate. The number of electrons transferred per O2 molecule reached 4.08 at a maximum. The catalytic activity of the catalyst was stable in long term measurements (150 times in 20 h) because a-C inherently has high corrosion resistance and oxygen-contained surface functionalities are stable in aqueous solution. Consequently, the a-C catalysts possessed high ORR reproducibility. [Display omitted] •Amorphous carbon based catalysts having higher activity and stability for ORR•Controlling activity toward ORR by introducing quinone and carboxy groups onto a-C surface•Surface-bonded quinone groups increasing the rate of O2 reduction to H2O2•Surface carboxy groups playing an important role in H2O2 reduction