Selective Formic Acid Production in Ni and NiFe Layered Hydroxides via Glycerol Electro-Oxidation

Abstract

Glycerol, a byproduct of biodiesel production, is a promising feedstock for conversion into high-value products through the glycerol electrochemical oxidation reaction (GEOR). Herein, a Ni-based layered double hydroxide (Ni LDH) catalyst is synthesized via hydrothermal synthesis to investigate the mechanism of the selective conversion of glycerol to formic acid (FA). The Ni LDH exhibits not only a high conversion rate of glycerol but also higher selectivity and Faradaic efficiency for FA at low potentials compared to NiFe LDHs. Through density functional theory (DFT) calculations, the delocalization of the pi-type bond between the adsorbed intermediate, glyceric acid (GLA), and the catalyst surface is found to activate GLA, leading to the preferential formation of FA through C-C bond cleavage at low potentials. Furthermore, with an understanding of the roles of OH- and glycerol concentrations in GEOR, controlling KOH and glycerol concentrations proves to be an effective way to enhance the selectivity and Faradaic efficiency of FA for the Ni LDH catalyst.