New insights on the selective electroconversion of the cellulosic biomass-derived glucose at PtAu nanocatalysts in an anion exchange membrane fuel cell

Abstract

Cellulosic biomass, which is basically a polymer of glucose, is the most abundant organic polymer on earth and there is significant interest in the development of advanced materials for its valorization through the waste-to-energy and water-to-chemical scenarios. Hence, a precise investigation of the monomer (glucose) electrooxidation in electrochemical reactors is a key starting point to tackle the whole cellulose and ultimately the entire biomass. To this end, we report herein new insights about the operation of a cogeneration direct alkaline glucose fuel cell (which includes an anion exchange membrane) that simultaneously produces electricity and mainly gluconate as the reaction product. The AuPt nanocatalysts of 3–5 nm particle size finely dispersed onto reduced graphene oxide (rGO) at a 20 wt% metal loading are obtained from an organic surfactant-free method, so-called the bromide anion exchange (BAE). Specifically, the electroanalytical investigation carried out with high-performance liquid ionic chromatography (HPLIC) and liquid chromatography coupled to mass spectrometry (LC-MS) demonstrate no carbon–carbon bond cleavage occurs, which represents an advance towards a CO2-free biomass valorization process. The comparison of the results commonly obtained in a three-electrode half-cell with those in an anion exchange membrane fuel cell shows that the trends in selectivity are the same. The fuel cell operation produces gluconate via a two-electron transfer process at 90% selectivity and 65% Faradaic efficiency. In addition to gluconate, glucuronate is also observed; both compounds are high value-added chemicals. This work contributes towards the engineering of novel electrocatalytic interfaces for the valorization of the surplus biomass into energy and chemicals.