Glucose electrooxidation on carbon supported NiAu electrocatalysts

NiAu/C nanomaterials are synthesised using a wet chemistry method with targeted Au atomic ratios of 10%, 20% and 30%. Physicochemical characterisations indicate that the materials have mean compositions close to the nominal ones but ca. 20 at% Au richer in average than expected (Au ratios of 13.6 at%, 23.1 at% and 35.9 at%, respectively). The NiAu/C materials are composed of Au-rich spherical-like Janus particles of several tenths nm and of a phase of very small Ni-rich nanoparticles and Ni(OH₂) clusters. The electrochemical measurements in a 0.1 M NaOH/0.1 M glucose electrolyte indicate that the NiAu20/C catalyst is the most active for the glucose oxidation reaction, leading to a mass activity at +0.6 V vs RHE more than 1.5 times higher than that with a pure Au/C catalyst, although the Au content is almost 5 times lower. The chronoamperometry measurements for 900 s at +0.6 V vs RHE confirm the activity gain with the NiAu20/C catalyst. The electrolysis measurement at a cell voltage of +Z+0.6 V for 6 hours shows that the NiAu20/C catalyst is selective towards the production of gluconic acid, with a faradaic efficiency higher than 100%, indicating the occurrence of a 1-electron reaction with anodic hydrogen coproduction. At +0.8 V, the faradaic efficiency is lower than 100 %, indicating the formation of other products than gluconic acid, but at a very low extent (not detectable by HPLC) guarantying a very high selectivity towards gluconic acid.