Controlled template removal from nanocast La0.8Sr0.2FeO3 for enhanced CO2 conversion by reverse water gas shift chemical looping

Abstract

This study addresses an enhanced CO2 conversion of mesoporous La0.8Sr0.2FeO3 (LSF) perovskite synthesized using a nanocasting method in reverse water gas shift chemical looping (RWGS-CL) process. The effects of controlled template removal from the nanocast LSF on its textural property and resulting redox reactivity were thoroughly investigated. LSF was first impregnated on SBA-15 (a mesoporous silica template), which was removed by NaOH etching to monitor the residual Si content. Specific surface area, total pore volume, and metal dispersion of the nanocast LSF were dramatically enhanced as the residual Si content decreased, but Si contents of < 5 wt% caused the mesoporous structure to collapse. Temperature-programmed experiments revealed that both the reactivity and capacity of reducible oxygen were maximized by optimizing residual Si content at 10 wt%. XPS analyses showed that the atomic ratio of surface oxygen to lattice oxygen, a key indicator of CO productivity, was also maximized at a Si content of 10 wt%. The mesoporous LSF with this Si content achieved the highest average CO yield of 2.80 mmol/g for RWGS-CL at 600 °C, which was 5.9 fold-higher than that achieved by bulk LSF.