Exploration of the reaction mechanism of the LaFeO3 oxygen carrier for chemical-looping steam methane reforming: a DFT study

Abstract

The CO conversion is expected to be controllable for chemical-looping steam methane reforming. Herein, density functional theory (DFT) calculations were employed to systematically explore the detailed reaction mechanism of CO conversion over the LaFeO₃ oxygen carrier. It is found that the FeO₂-terminated surface could exhibit better activity for CO adsorption than the LaO-terminated surface. In addition, the FeO₂-terminated surface is much more favorable for CO oxidation than the LaO-terminated surface and the Fe–O site is the main active site. The oxygen diffusion process is easier to proceed on the LaO-terminated surface compared with the FeO₂-terminated surface. Four pathways for the reaction process between the FeO₂-terminated surface and CO were proposed and oxygen diffusion was determined as the rate-limiting step. For the reaction of CO with the LaO-terminated surface, one pathway was considered and CO₂ desorption is the rate-limiting step. Comprehensively, the reactivity of CO conversion over the FeO₂-terminated surface is superior to that over the LaO-terminated surface. We could control the CO conversion by regulating the oxygen activity of LaFeO₃. This work provides guidance for the rational design of LaFeO₃ oxygen carriers in the CL-SRM process.