Anodic glycerol oxidation to formate facilitating cathodic hydrogen evolution with earth-abundant metal oxide catalysts

Substituting sluggish oxygen evolution reaction (OER) with glycerol electrooxidation reaction (GER) to formate is a promising strategy for addressing glycerol overproduction and hydrogen production efficiency concurrently. However, the poor formate selectivity and the use of noble-metal catalysts hamper electrolysis applications of glycerol. Herein, we present a commercial nickel foam-supported nickel cobaltite (NiCo2O4/NF) synthesized via a facile hydrothermal/annealing combined process. The as-synthesized earth-abundant metal oxide composite enables anodic GER to formate, achieving not only as low as potential of 1.23 V (vs. reversible hydrogen electrode, RHE) to deliver 10 mA cm−2, but also a large catalytic current density of 152 mA cm−2 with an exceeding formate faradic efficiency (FE) of 97 % at 1.6 V (vs. RHE). Synergy effect induced by intermetallic interactions of hierarchical NiCo2O4 nanostructures rooted in Ni foam substrate facilitates anodic oxidation of glycerol and assists cathodic hydrogen production simultaneously. In particular, a two-electrode electrolyser NiCo2O4/NF || Ni foam requires a cell voltage of as low as 1.35 V to achieve 10 mA cm−2, which is 320 mV lower than that of the conventional overall water splitting systems.