Over-faradaic hydrogen production in methanol electrolysis cells

Abstract A new alcohol electrolyser concept (Methanol Over-Faradaic Electrolyser: MOFE) has been developed to achieve over-faradaic H2 production rates, which were experimentally measured. In a first stage, this outstanding phenomenon was investigated in an alkaline membrane electrolyser. Secondly, a membrane-less electrolyser was used to simplify and implement this concept in practical configurations. The obtained results demonstrated that the experimentally measured over-faradaic H2 production rates on the cathode were due to the coupling of the electrocatalytic hydrogen production via methanol electrolysis (hydrogen evolution reaction) with the catalytic methanol dehydrogenation reaction. The kinetic of the latter reaction is drastically enhanced upon polarization due to the phenomenon of Electrochemical Promotion of Catalysis (EPOC), in liquid phase conditions. Hence, the K+ ions supplied to the Pd/C catalyst-cathode from the liquid electrolyte under polarization conditions promote the chemisorption of intermediate species, activating the catalytic hydrogen production via methanol dehydrogenation reaction on the active Pd sites. Thus, the synergy between these two processes (electrocatalytic + catalytic) lowers the overall energy requirements of the hydrogen produced below the typical values found for conventional alcohol electrolysis cells. These results demonstrate, for the first time, the possibility to produce an “over-faradaic” H2 production rate in a liquid phase electrolysis cell, which is of great interest in view of enhancing the energetic efficiency and the power requirements for hydrogen production via electrolysis of organic molecules.