PtAu alloying-modulated hydroxyl and substrate adsorption for glycerol electrooxidation to C3 products

Substituting the oxygen evolution reaction with the thermodynamically favorable glycerol oxidation reaction (GOR) in water splitting offers a promising approach to produce high-value chemicals in addition to hydrogen. However, the GOR suffers from the especially low selectivity towards the most-favored and value-added C3 products, and the current density of the GOR still remains unsatisfactory. Herein, we successfully prepared a novel self-supported honeycomb-like PtAu alloy catalyst on Ni foam (hp-PtAu/NF) for efficient electrocatalytic upgrading of glycerol to C3 chemicals at the anode coupled with cathodic H2 production. The hp-PtAu/NF anode shows high selectivity values for GOR conversion toward lactate and for total C3 products (70% and 95%, respectively) at 0.4 V vs. RHE. Impressively, 62% selectivity for C3 products over the hp-PtAu/NF electrode has been obtained at 1.6 V vs. RHE with an attractively high current density of 921.5 mA cm−2, compared to that (0.85%) on Pt/NF. Electrochemical in situ characterizations and theoretical calculations show that the introduction of Au can significantly facilitate the adsorption of hydroxyl species, thus elevating the GOR performance of hp-PtAu/NF. Meanwhile, the adsorption of glycerol molecule on the catalyst has been optimized to be a configuration of one terminal C atom, rather than two C atoms, being bonded on the catalyst surface by alloying Au with Pt, which effectively prevents the C–C bond from breaking into C2 or C1 chemicals and formation of poisonous carbonaceous intermediates, ensuring the high activity and C3 selectivity of the GOR over hp-PtAu/NF at enhanced current densities. This work illuminates the adsorption modulation mechanism of hp-PtAu/NF alloy catalyst and provides a promising electrocatalytic system for the co-production of value-added C3 products and H2 by a low-cost GOR approach in aqueous solutions.