Gas-free glycerol oxidation in a membrane-free electrolyzer for pure hydrogen and formate production with stable Ru-modified Co3O4 catalyst

Abstract

Membrane-free electrolyzers (MFEs) offer a promising, cost-efficient platform for hydrogen production by eliminating membrane-associated resistances. However, conventional MFE configurations often suffer from safety risks, hydrogen dilution, and product cross-contamination due to simultaneous generation of gaseous products at both electrodes. Here, we present an advanced MFE system coupling the hydrogen evolution reaction (HER) at the cathode with a gas-free glycerol oxidation reaction (GOR) at the anode, enabled by a highly active and durable Ru-modified Co3O4 catalyst. This strategic pairing achieved similar to 100 % FEH2, making hydrogen the sole gaseous output and facilitating seamless integration with downstream separation process. Compared to conventional membrane-based water electrolyzers operating with the oxygen evolution reaction (OER), our HER||GOR MFE system reduces the electricity cost of hydrogen production by up to 26.5 %, while simultaneously enhancing the anodic product value by 16.5-fold via selective formate generation. These results highlight a viable path toward economically and operationally superior hydrogen production systems.