Enhanced CO2 Conversion to CO by Silica-Supported Perovskite Oxides at Low Temperatures

Abstract

Repurposing of CO2 to valuable hydrocarbons is crucial for energy security and a balanced carbon cycle. Reverse water gas shift chemical looping (RWGS-CL) is capable of efficient CO2 to CO conversion at a low temperature of ∼600 °C with unprecedented rates using the La0.75Sr0.25FeO3 (LSF) perovskite-type oxide amalgamated with silica. The LSF/SiO2 composite (25% LSF by mass) promotes a notable extent of oxygen vacancies in the active phase, a key parameter for CO2 conversion. In each of eight RWGS-CL cycles, CO generation yields of LSF/SiO2 surpass those of LSF alone by about 200%, producing 2.6 mmol of CO gLSF–1 at a peak rate of 0.8 mmol CO gLSF–1 min–1. This significant improvement is concomitant with a decreased average LSF crystallite size retained at these low thermochemical reaction temperatures. Evidence of this enhancement points to perovskite particle size reduction by silica, lattice strain induced by the support, and curtailed quantities of secondary phases that limit accessibility to active s...