Abstract

We investigate the application of the onion-like carbon (OLC) as an electrocatalyst for [VO]2+/[VO2]+ redox flow reaction; its performance (electrocatalytic activity and reversibility) strongly increases with the synthesis to peak at 1800 °C in 1000–2000 °C range. The dopant/modification-free, optimized redox performances of the OLC is comparable to some of the best data in the literature of various types of carbon materials with post-synthesis modifications or doping. Mechanism behind such performance optimization is investigated employing various physical/electrochemical analyses as well as the first-principles calculations. We demonstrate that the carbon dangling bonds or the crystalline defects, generated by an inherent mechanism unique to the OLC, played a pivotal role in determining the electrocatalytic performances.