Multi-site catalysis of high-entropy hydroxides for sustainable electrooxidation of glucose to glucaric acid

Abstract

The glucose electrooxidation reaction (GOR) is an environmentally benign way to generate high value-add glucaric acid. However, a lack of suitable catalysts for the GOR limits development. Here we report for the first time a practically robust, multi-site, synergistic catalyst of defect-rich high-entropy FeCoNiCu layered double-hydroxide nanosheets grown on nickel foam. We demonstrate a highly significant activity and stability for the GOR leading to a low potential of 1.22 V vs. RHE at a current density of 100 mA cm⁻², together with an excellent glucose conversion of ∼100% and glucaric acid yield of >90%. We evidence that the Cu–Co bridge promotes dehydrogenation of the hydroxyl group, and that the Cu–Cu bridge boosts dehydrogenation on carbon to form an aldehyde group. We establish that the Cu–Ni bridge boosts the oxidation of the aldehyde group to carboxyl to exhibit an important advantage of multi-site synergistic catalysis of high entropy hydroxides. We confirm an energy-saving hybrid flow electrolytic cell, prototype coupled GOR with a nitrate reduction reaction (NO₃⁻RR), that requires an applied voltage of just 1.07 and 1.32 V for an electrolytic current density of, respectively, 10 and 100 mA cm⁻² for GOR‖NO₃⁻RR, together with concurrent low-potential production of glucaric acid and NH₃. We conclude that defect-rich high-entropy FeCoNiCu catalysis of high-entropy hydroxides can be used for the practical design of sustainable and environmentally benign electrooxidation of glucose to glucaric acid. Our findings will be of benefit to researchers and manufacturers in the electrocatalytic conversion of renewable biomass for high value-add chemicals.