Electrochemical control of the RWGS reaction over Ni nanoparticles deposited on yttria stabilized zirconia

Abstract

Transition metal oxides are promising candidates for the activation of the reverse water gas shift (RWGS) reaction. The in situ formation and stabilization of these oxides appears to be a key challenge in achieving 100% selectivity towards CO in a CO₂ hydrogenation reaction system. In the present study, electrochemistry is utilized to modify the catalyst work function, thus the strength of the bonds of the adsorbed species (EPOC effect) as well as to in situ form and stabilize nickel oxide on an oxygen ion conductor/solid electrolyte. Both actions, electrochemical promotion of catalysis (EPOC) and electrochemical oxidation appear to promote the RWGS activity. The electro-oxidation of nickel is investigated using cyclic voltammetry (CV) measurements, revealing the formation of surface NiO_x species at the metal-electrolyte-gas three-phase boundaries (tpb). Application of positive polarization is the driving force for the in situ electro-oxidation of the Ni particles due to oxygen ion (i.e., O²⁻) migration from the solid electrolyte to the catalyst surface through the tpb. The present results aim to further extend the applicability of the EPOC effect in the modern heterogeneous catalysis industry as a powerful tool for in situ catalyst activation and regeneration.