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In addition to their applications in the construction of fuel cells, hydrogen separators and sensors, solid state proton (H+) conductors can be used as the main component of catalytic and electrocatalytic reactors. Their advantage, compared to low-temperature proton conductors, is that they can operate in a temperature range within which the kinetics of several industrially important catalytic hydro- and dehydrogenation are acceptably fast. In most of the applications of H+ cell reactors in catalytic research, the reaction of interest takes place on the working electrode while the counter electrode serves for the formation of protons from a hydrogen containing compound. These reactors, however, would become more competitive if useful chemicals were produced on both, working and counter electrode [1, 2]. Results on two reaction systems in which both, cathode and anode were properly utilized are presented here. The aim of this study is the electrochemical production of methanol from carbon dioxide and steam, in a co-ionic conducting solid electrolyte cell at atmospheric pressure. Steam and CO2 are introduced at the anode and cathode side, respectively, of a co-ionic (H+ and O2-) conductor. Steam is electrolyzed to form O2 and protons (H+). The latter are transferred to the cathode and react with CO2 to form CH3OH. The second system is an electrochemical Haber-Bosch (H-B) Process [3, 4]. A mixture of steam and methane is fed over the anode (a Ni-composite electrode) and gaseous N2 is fed over the cathode (VN-Fe). Hydrogen extraction from the steam reforming compartment, enhances the thermodynamically limited methane conversions, whereas 5-14% of the protons pumped are converted to ammonia. A protonic ceramic fuel cell is used to recover electricity and separate nitrogen from ambient air by exploiting by-product hydrogen. This process could potentially require less energy and release fewer CO2 emissions than its conventional counterpart. References: [1] A.Vourros, V. Kyriakou, I. Garagounis, E. Vasileiou,M. Stoukides, Solid State Ionics, 306 (2017) 76-81. [2] S.H. Morejudo, R. Zanon, S. Escolastico, I. Yuste, H. Malerød-Fjeld, P.K. Vestre, W.G. Coors, A. Martínez, T. Norby, J.M. Serra, C. Kjølseth, Science, 353 (2016) 563-566. [3] I. Garagounis, A.Vourros, D. Stoukides, D. Dasopoulos, M. Stoukides, Membranes 9 (2019) 2-17. [4] V. Kyriakou, I. Garagounis, A. Vourros, E. Vasileiou, M. Stoukides, JOULE, in press, (2019) |
