Extensive use of fossil fuels and consequential high levels of carbon dioxide (CO
2) emissions are major contemporary challenges.
[1] The most direct way to mitigate this process is to activate reverse chemical pathways in which CO
2 is reduced into high-energy molecules.
[2] The electrochemical reduction of CO
2 to CO has attracted increasing attention, since CO represents a valuable intermediate to the production of synthetic fuels using established processes, such as Fischer-Tropsch.
[2, 3] One attractive approach to electrochemically reduce CO
2 to CO is the use of solid oxide electrolysis cells (SOECs)
[4]. SOECs are solid-state electrochemical systems that, in principle, can facilitate the electrochemical reduction of CO
2 to CO with potentially very high rates due to favorable kinetics at high operating temperatures
[2, 4]. While electrochemical reduction of CO
2 using SOECs offers a great deal of promise, these systems are still limited by the high activation overpotential losses induced by the sluggish CO
2 reduction kinetics at the cathode.
[1, 4] Moreover, the current knowledge on the electrochemical reduction of CO
2 using SOECs is mainly limited to proof-of-concept experiments, demonstrating the viability of its operation. Lack in understanding of the governing mechanism for electrochemical reduction of CO
2 on SOECs, as well as, the catalytic role played by different cathode components (i.e., metal and the mixed metal oxides) make the optimization of the SOEC cathode activity very challenging. In the present work, we combine experimental and theoretical techniques to understand the chemical/electrochemical steps that govern CO
2 electrolysis on metals under SOEC conditions. Controlled electrochemical studies are used to investigate the role played by the metal and the mixed metal oxide cathode components toward the electrochemical reduction of CO
2. Structure/performance relations are developed in order to identify optimum cathode compositions for this process.
REFERENCES
[1] S.D. Ebbesen, S.H. Jensen, A. Hauch, M.B. Mogensen, High temperature electrolysis in alkaline cells, solid proton conducting cells, and solid oxide cells, Chemical reviews, 114 (2014) 10697-10734.
[2] X.-K. Gu, J.S.A. Carneiro, E. Nikolla, Heterogeneous electrocatalysts for CO2 reduction, in: Catalysis, 2017, pp. 94-121.
[3] K. Xie, Y. Zhang, G. Meng, J.T. Irvine, Direct synthesis of methane from CO 2/H2O in an oxygen-ion conducting solid oxide electrolyser, Energy & Environmental Science, 4 (2011) 2218-2222.
[4] X.-K. Gu, J.S. Carneiro, E. Nikolla, First-Principles Study of High Temperature CO2 Electrolysis on Transition Metal Electrocatalysts, Industrial & Engineering Chemistry Research, 56 (2017) 6155-6163.
