Catalytic action of rare earth oxide (La2O3, CeO2, Pr6O11) on electrochemical oxidation of activated carbon in molten KOH–NaOH

Abstract

The oxidation of anode carbon fuel directly affects the electrochemical performance of molten hydroxide direct carbon fuel cell (MHDCFC). In general, the anode carbon fuel can be oxidized at high temperature, thus the direct carbon fuel cell (DCFC) can show great electrochemical performance. In this study, rare earth oxides (La2O3, CeO2, Pr6O11) were prepared by the method of precipitation. Activated carbon was prepared by pretreatment of lignite. Rare earth oxides and activated carbon were mixed as anode carbon fuel, and rare earth oxides were used to catalyze the electrochemical oxidation of anode carbon fuel. The results show that CeO2 has better electrocatalytic activity compared with La2O3 and Pr6O11 in the MHDCFC. The electrochemical test results show that the current density (at 0.4 V) increases from 81.02 to 112.90 mA/cm2 and the maximum power density increases from 34.78 to 47.05 mW/cm2 at 450 °C, when the mass fraction of CeO2 is increased from 0 to 40%. When the mass fraction of CeO2 is 30%, the current density (82.55 mA/cm2 at 0.4 V) at 400 °C is higher than that (81.02 mA/cm2 at 0.4 V) without CeO2 at 450 °C. The electrochemical oxidation mechanism of CeO2 catalyzed anode carbon fuel is discussed.