ReaxFF reactive molecular dynamics study on electrochemistry of H2/CO hybrid fuel in Ni/YSZ anode

Abstract

Fuel flexibility, e.g. using reformate or syngas fuel directly, is one of the most advantages of solid oxide fuel cells (SOFC). However, the electrochemical mechanism of the H2/CO mixture, which is common and key in hydrocarbon fuel-fed SOFC, is unclear and relatively rarely studied at present. This article makes Reactive Force-Field (ReaxFF) reactive molecular dynamics (RMD) simulations on the electrochemical co-oxidation of H2/CO hybrid fuel in Ni (nickel)/YSZ (yttria-stabilized zirconia) anode. The RMD simulations at different fuel gas components show that in the H2/CO/Ni/YSZ system the H2 conversion rate maintains the maximum (100%), and the conversion rate of CO improves compared with that of pure CO fuel in the case of 30%H2−70%CO. Two ways of CO2 generation are found: one is that the CO(Ni) species formed by the adsorption and activation of CO on the Ni surface is oxidized by the lattice oxygen; the other is the oxidation of CO(Ni) by spillover atomic oxygen, which is adsorbed on the Ni surface. It is worth noting that the effect of oxygen vacancies on the oxidation of CO is more significant than that of H2. A viewpoint is proposed to explain how H2 enhances the oxidation of CO. The results help understand the electrochemistry of H2/CO involved fuel in the context of SOFC operations.