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.