Selective electro-oxidation of glycerol over Co-based ZIF-67 derived catalyst

Abstract

The increasing global energy demand has necessitated a lookout for newer renewable sources of energy that could replace or decrease the dependency of non-renewable sources i.e. fossil fuel. Hydrogen can be used as fuel and can be produced in various ways and one of the most effective means is by electrochemical water splitting. Hydrogen and oxygen are produced at the cathodic and anodic half-cells of the electrolyzer, respectively. However, due to the sluggish kinetics for the oxygen evolution reaction, the overall cost-effectiveness of the system decreases significantly. This could be overcome by using glycerol oxidation as the anodic half-cell reaction in the electrolyzer having a lower theoretical oxidation potential than water, cogenerating value-added products alongside. In this report, Co-based ZIF-67 (cobalt-based zeolitic imidazolate framework) a sub-category of metal-organic framework (MOF) has been pyrolyzed and used as an electrocatalyst for the glycerol oxidation reaction (GOR) where the ZIF is acting as a self-sacrificial template for a nitrogen-doped carbon matrix with metal nanoparticles dispersed within it. Morphological studies were carried out for the catalyst using techniques like SEM, TEM and PXRD. Different electrochemical cell setups like a rotating disk, H-cell and flow-through cells were used to investigate the activity and stability of the catalyst. Product selectivity for the catalyst was examined using techniques like HPLC, NMR and in-situ IR. Different products could be identified like formic acid, glyceric acid and carbonate with formic acid being the major product. Glyceric acid was also formed in substantial amounts.