Enhanced dehydrogenation kinetics for ascorbic acid electrooxidation with ultra-low cell voltage and large current density

Abstract

Dehydroascorbic acid (DHA) production from ascorbic acid electrochemical oxidation (AAOR) can be used to upgrade biomass derivatives and hydrogen production with low energy consumption. Carbon materials are a promising class of nonmetal AAOR electrocatalysts; however, their performance does not meet the requirements for practical applications. In this study, an oxygen-containing group (OCG)-modified carbon electrocatalyst was prepared via oxygen plasma treatment. It could drive a current density of 100 mA cm−2 at only 0.65 VRHE and realize a Faradaic efficiency of over 90% for DHA production with long-term stability of 20 h. A proton exchange membrane-type electrolyzer integrating the anodic AAOR and the cathodic hydrogen evolution reaction (HER) was assessed. It only requires a cell voltage input of 0.98 V to deliver a current density of 1000 mA cm−2, which is superior to most reported organic upgrading reactions. Moreover, it only needs 1.54 kWh to produce normal cubic H2, which is one-third of that of traditional water electrolysis. Importantly, the contribution of each type of OCG was investigated by combining electrochemical measurements and theoretical calculations. It was revealed that the OCGs, especially the carboxyl groups (–COOH) of carbon materials, could enhance the dehydrogenation kinetics of the AAOR, thereby boosting the electrocatalytic activity. This study presents a low-energy and eco-friendly strategy for electrochemical biomass upgrading and hydrogen production, provides an in-depth understanding of the role of oxygen-containing functional groups in the AAOR, and guides the design of carbon-based electrocatalysts for AAOR.