Suppressing product crossover and C–C bond cleavage in a glycerol membrane electrode assembly reformer

Abstract

Generating hydrogen through water electrolysis is impeded by high costs and substantial energy consumption mainly due to high equilibrium potential and sluggish kinetics of the oxygen evolution reaction (OER). Glycerol oxidation reaction (GOR) is proposed as an alternative due to its low thermodynamic limit and value-added oxidation products. However, GOR in membrane electrolyzers faces challenges in achieving industrial-scale current densities as well as in addressing crossover issues. Here, we investigated five different membrane electrode assembly (MEA) configurations to perform GOR with various ion exchange membranes and catholyte. After systematic study, we present an innovative acid–alkali asymmetric cell design which operates with alkaline anolyte and acidic catholyte for electrochemical neutralization energy (ENE) harvesting to improve energy efficiency. The product anions crossover via anion exchange membrane (AEM) is also impeded since that the increasing concentration gradient-driven hydroxide ion crossover occupying the anion exchange channels in AEM and thus limits the product crossover of AEM. Such device also demonstrates the capability of impeding C–C bond cleavage to promote high-value C3 products generation and reduce carbon emission due to the lower degree of cell polarization and limited hydroxide ion supply at anode. Eventually, a whole-cell potential can be significantly reduced to 0.377 V while achieving a current density of 200 mA cm⁻². Moreover, total faradaic efficiencies (FEs) of 55% and 84% for all C3 products and all liquid products can be achieved at a current density up to 1000 mA cm⁻².