Enhancement of Ni oxidation tolerance in Ni/GDC cathode surface during CO2/H2O electrolysis in SOEC

Abstract

The enhancement of Ni oxidation tolerance in a Ni/GDC cathode during CO₂/H₂O electrolysis in a solid oxide electrolysis cell was investigated through experiments and first-principle density functional theory (DFT) calculations. Ni oxidation was considerably suppressed in the Ni/GDC cathode in the absence of H₂ during CO₂/H₂O electrolysis, whereas Ni oxidation occurred in the Ni/YSZ cathode. A decrease in the H₂/CO ratio in Ni/GDC suggested that the reverse water–gas shift reaction was enhanced owing to the presence of active GDC surfaces with extra vacancies. DFT calculations revealed that the activation barriers for cathodic reactions at triple-phase boundary (TPB)—including CO₂ adsorption on Ni, CO₂ dissociation into CO and O, and O migration from the Ni surface to the electrolyte—were nearly identical in Ni/YSZ and Ni/GDC. Instead, O migration from the Ni surface to extra vacancies in the GDC surface improved Ni oxidation resistance in Ni/GDC during CO₂/H₂O electrolysis.