Caustic aqueous phase electrochemical reforming (CAPER) of ethanol for process intensified compressed hydrogen production

Abstract

The Caustic Aqueous Phase Electrochemical Reforming (CAPER) process can convert aqueous-phase ethanol to high-pressure and high-purity hydrogen (H2) at lower cell operating temperatures and voltages than traditional methods. Additionally, any carbon dioxide (CO2) produced by the ethanol electrochemical oxidation is captured by the caustic electrolyte solution. Without using a membrane, the only gas-phase species is H2. The CAPER process achieves process intensification for compressed and pure H2 production by eliminating the need for downstream separation and external compression steps. All the compression is performed on the liquid-phase reactants to circumvent less efficient gas-phase compression. This study uses a high-pressure batch electrochemical reactor to demonstrate the capability of the CAPER reforming process and investigates catalytic behavior under operating conditions. Our Tafel analysis showed that both palladium and platinum nanoparticles on carbon supports have high activity for ethanol electrooxidation under the caustic electrolyte condition (exchange current density (i0) > 1 × 10−5 A cm−2), while non-noble nanoparticles on carbon supports showed poor activity. The only gas phase product was pressurized H2 and its faraday efficiency was determined as 100%. The exchange current density was not affected by high-pressure operation. The carbon selectivity toward unwanted byproduct acetate on the anode increased from 17% to 63% as the applied anode potential increased from −500 mV to −200 mV vs. Ag/AgCl.