Single-phase nickel-doped ceria cathode with in situ grown nickel nanocatalyst for direct high-temperature carbon dioxide electrolysis

This paper reports the in situ growth of Ni nanocatalysts to anchor onto the CeO2 surface to combine the surface oxygen vacancies and form heterogeneous catalysis sites with the aim of improving electrocatalytic activity through direct exsolution of Ni nanoparticles from the Ni-doped CeO2 lattice in a reducing atmosphere at higher temperatures. The combined use of XRD, TEM, SEM and XPS confirms the in situ exsolution of Ni nanoparticles on the CeO2 surface. The doping of CeO2 with nickel leads to a charge redistribution and an increase of oxygen vacancy concentration. The electrical properties of Ce1-xNixO2 (x = 0, 0.05, 0.10, 0.15 and 0.20) are systematically investigated and correlated to their electrochemical performance in symmetrical and electrolysis cells. The electrical properties and electrochemical performances improve with increasing Ni contents. The Ce0.85Ni0.15O2 cathode with anchored Ni nanocrystal shows the best electrochemical performances for carbon dioxide electrolysis with reasonable short-term stability; however, the electro-catalytic activity of Ce0.8Ni0.2O2 with excess Ni particles on the surface rapidly decays because of adverse agglomeration of Ni particles at high temperatures.