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

Abstract

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.