Modular Solar-to-Fuel Electrolysis at Low Cell Potentials Enabled by Glycerol Electrooxidation and a Bipolar Membrane Separator.

Abstract

Solar fuel generation through water electrolysis or electrochemical CO2 reduction is thermodynamically limited when it is paired with oxygen evolution reaction (OER). Glycerol electrooxidation reaction (GEOR) is an alternative anodic reaction with lower anodic electrochemical potential that utilizes a renewable coproduct produced during biodiesel synthesis. We show that GEOR on an Au-Pt-Bi ternary metal electrocatalyst in a model alkaline crude glycerol solution can provide significant cell potential reductions even when paired to reduction reactions in seawater and acidic catholytes via a bipolar membrane (BPM). We showed that the combination of GEOR and a BPM separator lowers the total cell potential by 1 V at an electrolysis current of 10.0 mA cm-2 versus an anode performing anode's OER when paired with hydrogen evolution and CO2 reduction cathodes. The observed voltage reduction was steady for periods of up to 80 h, with minimal glycerol crossover observed through the membrane. These results motivate new, high-performance cell designs for photoelectrochemical solar fuel integrated systems based on glycerol electrooxidation.