Progress and Challenges in Electrochemical Glycerol Oxidation: The Importance of Benchmark Methods and Protocols

Abstract

Electrochemical oxidation of glycerol presents a strategy to utilize the glycerol byproduct from biodiesel production to co-generate valuable liquid products at the anode and green hydrogen at the cathode, with lower energy requirement than conventional water electrolysis, offering both environmental and economic benefits. This review summarizes recent advancements in electrocatalyst development for glycerol electro-oxidation and highlights the challenges posed by its complex reaction mechanisms, including wide product distribution, multiple binding configurations of reaction species, unstable intermediates, and the coexistence of both Faradaic and non-Faradaic pathways, all of which complicate the identification and quantification of glycerol derivatives using chromatographic and spectroscopic techniques. The review emphasizes the need to establish standardized protocols for electrochemical measurements that are scalable and transferable from rotating disk electrodes (RDE) to membrane electrode assemblies (MEA), as well as for product detection and quantification using high-performance liquid chromatography (HPLC). To enable intra-laboratory comparisons, researchers should provide detailed specifications of experimental setups, conditions, and methodologies for evaluating electrochemical activity, catalyst durability, and calibration standards for product quantification via HPLC. Consistency in reporting experimental data, particularly regarding product selectivity, is crucial but often overlooked. Lastly, this paper discusses the potential of applying in situ techniques to understand the reaction mechanisms at the molecular level and to distinguish between Faradaic and non-Faradaic reaction pathways, while addressing the limitations and difficulties of applying these techniques.