Study of the performance of glucose anomers in a hydroxide anion exchange membrane electrolyzer operating with pulse electrodeposited gold for paired electrosynthesis

Abstract

Electroconversion (also known as electroreforming) of biomass-derived compounds is currently attracting considerable interest, with the aim of lowering cell voltage during electrolysis to co-produce a number of decarbonized energy carriers or chemical intermediates (hydrogen, ammonia, gluconate, etc.). Naturally, d-glucose, which represents a study model for the electro-valorization of cellulosic biomass into value-added chemicals such as gluconate, is in fact a mixture of two anomers called α-d- and β-d-glucose. The β-d-glucose anomer is the monomer unit of cellulose, while the α-d-glucose anomer is the monomer unit of starch. In this contribution, we therefore investigate whether or not the nature of the glucose substrate can influence electrolysis cell performance, or whether the use of d-glucose alone can represent the true picture of biomass feeding an electrolysis cell. Free-standing electrocatalysts ready for use in a membrane-electrode assembly were synthesized using a pulsed electrodeposition methodology to control the deposition of gold and platinum particles on the microfibers of a low-metal gas diffusion electrode (GDE). We developed GDE-Au (82 μgAu cm−2, 0.88 wt%) to catalyze the selective electrooxidation of glucose into gluconate, and GDE-Pt (33 μgPt cm−2, 0.36 wt%) to catalyze the hydrogen evolution reaction (HER). While half-cell studies showed no significant difference, for the glucose-fed electrolysis cell, α-d-glucose leads to a much higher current density compared to d-glucose and β-d-glucose for cell voltages above 0.5 V, leading to 85.6 ± 17.1, 44.3 ± 8.8 and 30.5 ± 0.8 mA cm‒2 for α-d-glucose, β-d-glucose, and d-glucose, respectively, at 1 V.