High-Current-Density Glycerol Electrooxidation on S-Cu-Ni/NF Catalyst: Unveiling the Synergy between S-Promoted GOR...

Electrocatalytic glycerol oxidation reaction (GOR) coupled with hydrogen evolution reaction (HER) is an ideal method to achieve efficient hydrogen production. However, realizing the stable degradation of glycerol to formate at high current densities still faces great challenges, mainly stemming from the competition between GOR and oxygen evolution reaction (OER) at high potentials. To address this issue, in this study, S-Cu-Ni/NF catalysts were successfully synthesized using Cu-Ni/NF catalysts as precursors. The introduction of Cu effectively suppressed the OER, enabling the catalysts to achieve more than 75% formate Faraday efficiency over a wide potential range from 1.3 V vs RHE to 1.6 V vs RHE. Meanwhile, S doping significantly enhanced the electron transport ability of GOR, enabling the S-Cu-Ni/NF catalyst to achieve a high current density of 100 mA cm^-2 at a low potential of 1.395 V vs RHE. In addition, after 24 h of continuous operation at a high current density of 100 mA cm^-2, the catalyst potential increased by only 40 mV, demonstrating excellent stability. Scanning electron microscopy with energy dispersive spectra (SEM-EDS), X-ray photoelectron spectra (XPS) and in situ Raman characterization confirmed that the precipitation of S promoted the formation of the active site NiOOH and its dynamic growth during the GOR process. The present study not only improved the selectivity of formate at high potentials by inhibiting OER but also significantly enhanced the GOR performance, demonstrated the potential of stable degradation of glycerol at high current densities, and provided a feasible strategy for the industrial application of glycerol oxidation coupled with hydrogenolysis.