Proton ceramic electrochemical reactors for sustainable hydrogen production

Electrochemical gas separation emerges as an attractive technology as the cost of electricity declines. Proton ceramic electrochemical reactors (PCERs) extract hydrogen from reaction mixtures and can offer a compact and efficient approach to hydrogen production [1]. Because of the solid-state and gas-impermeable nature of the membrane, the hydrogen produced can in principle be entirely free of impurities, as unreacted molecules cannot get to the other side of the membrane. Through a one-step process, balancing the energy from the endothermic reactions with the separation and compression of hydrogen allows for much higher efficiencies compared with other hydrogen production technologies. In the case of CH4 reforming, the possibility of extracting H2 at conditions suitable for the reforming reaction enables the overcome of the thermodynamic limitations in terms of CH4 conversion. Furthermore, the electrochemical H2 compression allows to go beyond the driving force limitation of traditional membrane reactors (based for example on Pd membranes). PCERs offer attractive performance including mechanical stability and chemical robustness over a wide range of temperatures (300–800 °C) and pressure conditions (> 50 bar). In our recent work [2], we demonstrate the upscaling of an efficient 36 cell x 15 cm2 reactor with coupled heat, reaction and current distribution. Hydrogen extraction > 99 % shows complete conversion of CH4 for conditions relevant both for natural gas and biogas, and a hydrogen purity up to 99.995 %. The by-product leaving the reactor is a concentrated CO2 stream, which can facilitate the implementation of efficient carbon capture. The results suggests that proton ceramic electrochemical reactors can offer the lowest CO2 intensity for on-site hydrogen production. Furthrmore, to expand on the wide applicability and flexibility of the proposed technology, cell performance for ammonia decomposition will be presented, showing similar conversion with both anhydrous and aqueous NH3.