Hydrogen and acrylate generation by electrochemical reforming of bioalcohols

The production of hydrogen by the electrolysis of water is a well-established technology. However, it does not have a significant commercial impact due to its high-energy cost. A traditional Proton Exchange Membrane (PEM) electrolyzer needs more than 45 kWh kgH2-1 to achieve a significant rate of hydrogen production. This is the main reason why water electrolysis accounts for only a small proportion of the world's hydrogen production (circa 4%). Since the thermodynamic barrier of water electrolysis consumes 68% of the whole energy input of the device, our strategy for reducing the energy cost is the replacement of the unfavorable anodic oxygen evolution reaction with a more suitable reaction: the partial oxidation of an alcohol to a carboxylate. This process needs only 20 kWh for the evolution of one kilogram of hydrogen at the same working conditions of traditional PEM electrolyzers, with a net energy saving of about 44%. Such electrolytic processes that lead to the concomitant generation of hydrogen and industrially relevant chemicals, like acetate and lactate, are often indicated as "electrochemical reforming", or "electroreforming". In order to obtain selective oxidation of alcohols to carboxylic compounds of interest to the fine chemical industry, several anodic catalysts have been investigated, ranging from nanostructured palladium catalysts to rhodium organometallic compounds. Here we present an anode based on palladium nanoparticles deposited onto a carbon-ceria support Pd(10%)/C:CeO2 (50%/50%) which is able to selectively oxidize the 1,3-propanediol biomass derived alcohol to potassium acrylate, a very important raw chemical. The production of acrylate is coupled with the generation of pure hydrogen (99.99%). We had and in depth study of the operative conditions of the electroreformer to optimize the selectivity of the alcohol oxidation reaction to potassium acrylate: at 400 mV and 80°C in a "single pass mode", the selectivity is of the 80% for acrylate.