Saturated Alcohols Electrocatalytic Oxidations on Ni-Co Bimetal Oxide Featuring Balanced B- and L-Acidic Active Sites

Abstract Investigating structural and hydroxyl group effects in electrooxidation of alcohols to value-added products by solid-acid electrocatalysts is essential for upgrading biomass alcohols. Herein, we report efficient electrocatalytic oxidations of saturated alcohols (C 1 -C 6 ) to selectively form formate using NiCo hydroxide (NiCo–OH) derived NiCo 2 O 4 solid-acid electrocatalysts with balanced Lewis acid (LASs) and Brønsted acid sites (BASs). Thermal treatment transforms BASs-rich (89.6%) NiCo–OH into NiCo 2 O 4 with nearly equal distribution of LASs (53.1%) and BASs (46.9%) which synergistically promote adsorption and activation of OH − and alcohol molecules for enhanced oxidation activity. In contrast, BASs-enriched NiCo–OH facilitates formation of higher valence metal sites, beneficial for water oxidation. The combined experimental studies and theoretical calculation imply the oxidation ability of C 1 -C 6 alcohols increases as increased number of hydroxyl groups and decreased HOMO–LUMO gaps: methanol (C 1 ) < ethylene glycol (C 2 ) < glycerol (C 3 ) < meso-erythritol (C 4 ) < xylitol (C 5 ) < sorbitol (C 6 ), while the formate selectivity shows the opposite trend from 100 to 80%. This study unveils synergistic roles of LASs and BASs, as well as hydroxyl group effect in electro-upgrading of alcohols using solid-acid electrocatalysts.