Performance enhanced of Ni Ce0.8Sm0.2O1.9 hydrogen electrode for reversible solid oxide cells with cadmium substitution

Abstract

Ni1-xCdxO-SDC composite materials are prepared and investigated as the hydrogen electrodes for reversible solid oxide cell (RSOC). XRD, SEM, XPS and Raman techniques have been used to characterize structural properties, textural and mobility of adsorbed oxygen and lattice oxygen. After reduction, Cd is incorporated into the lattice of Ni and formed NiCd alloy. The reduced Ni0.9Cd0.1O-SDC possesses the most oxygen vacancies, resulting in the highest catalytic activity for the electrochemical oxidation of H2 and the electrolysis of H2O. The electrochemical oxidation process of H2 on the hydrogen electrode in solid oxide fuel cell (SOFC) mode is investigated with a symmetric cell under various H2 partial pressures. The surface diffusion of adsorbed H atom on the reduced Ni1-xCdxO-SDC composite hydrogen electrodes is the rate-determining step (RDS) for H2 electrochemical oxidation reaction and the reduced Ni0.9Cd0.1O-SDC shows the highest electrochemical oxidation rates. The maximum power densities (Pmax) of the cells with reduced Ni0.9Cd0.1O-SDC as hydrogen electrode is 796.2 mW cm−2 when using H2 as the fuel at 700 °C. Furthermore, in solid oxide electrolysis cell (SOEC) mode, the cell with reduced Ni0.9Cd0.1O-SDC as hydrogen electrode exhibits the best electrolysis performance under various H2O concentrations and the current densities remain stable during the test at different voltages for a total period of 10 h under 47%H2O + 53%H2O atmosphere at 700 °C.