High-temperature electrolysis of CO2 and H2O in a solid oxide electrolysis cell (SOEC) is a promising renewable technology for synthesis gas (a mixture of H2 and CO) production. An SOEC consists of an O2- ion conducting electrolyte (yttria- stabilized zirconia, YSZ), a cathode that carries out the following half reactions: CO2+2e-→CO+O2-, H2O+2e-→H2+O2-, and an anode performing the oxygen evolution reaction: 2O2-→O2+2e-. The main challenge behind the development of SOEC is designing a high- performance cathode catalyst. In this study, Ni and Co- doped lanthanum strontium ferrite perovskite oxide (ABO3, A= La/Sr, B= Ni/Co/Fe) cathodes were used for co-electrolysis of CO2 and H2O at 800°C. Effect of A-site stoichiomtery on the surface basicity was investigated using XPS, FTIR and CO2 temeprature- programmed desorption experiments, and it was found that a high surface basicity of the cathodes led to formation of coke during CO2 elctrolysis. Effect of B-site doping with Ni and Co on the physical and chemical properties of these materials were characterized using XRD, XPS, Raman, conductivity measurement, DRIFTS, XANES and temperature-programmed experiments. Their electrocatalytic activities for CO2 and H2O co-electrolysis were measured using an SOEC consisting of YSZ electrolyte and a L0.8Sr0.2MnO3 (LSM)-YSZ anode. The Faradaic efficiency for H2 and CO production was much higher for the Ni- doped cathode than the Co- doped cathode. Moreover, H2/CO ratio in the produced synthesis gas was observed to be a function of the nature of the B-site dopant. In general, this ratio was found to increase with Ni- content, whereas decrease with Co- content. Operando XANES under electrolysis conditions and in-situ DRIFTS experiments with CO2+H2O adsorption- desorption were conducted to understand the reasons behind such differences in the performances achieved from the Ni- doped and Co- doped materials.

High-temperature electrolysis of CO2 and H2O to produce synthesis gas with controllable H2/CO composition on a Ni- and Co-doped lanthanum strontium ferrite cathode

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.