Ce-enhanced LaMnO3 perovskite catalyst with exsolved Ni particles for H2 production from CH4 dry reforming

Abstract

Ce was successfully doped into the A site of La_0.9Mn_0.8Ni_0.2O₃ (LMN) with 5 mol% doping content (LCMN-05), and the obtained LCMN-05 acted as a catalyst for dry reforming. After reduction in 5% H₂–N₂ stream at 800 °C, the Ni particles were successfully exsolved on the surface. The H₂-TPR, XPS and solid EPR results demonstrated that the Ce substitution facilitated the reducible properties of the perovskites, as well as the oxygen transfer. Furthermore, it promoted the reduction to high extents with more oxygen vacancies left behind. Thus, the reduced LCMN-05 showed stable conversions of CH₄/CO₂ above 90% at 750 °C for 50 h without coking. While for the reduced LMN, it had a rapid deactivation with the amount of carbon fibers when the temperature rose from 700 °C to 750 °C. The LCMN-05 displayed a whole perovskite structure after the test, which guaranteed the strong interaction between the exsolved Ni and perovskite substrate. However, the structure of LMN was destroyed in a reducing atmosphere at high temperature, which explained the different performances of the two catalysts. The introduction of Ce increased the amount of oxygen vacancies and avoided the excessive reduction of Mn³⁺, thus improving the structural stability and ensuring the catalytic activity of reduced LCMN-05.