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

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 La_0.75Sr_0.25FeO₃ (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 2.60 mmol CO g_LSF^-1 at a peak rate of 0.8 mmol CO g_LSF^-1 min^-1. This significant improvement is concomitant with a decreased average LSF crystalline size retained at these low thermochemical reaction temperatures. Evidence of this enhancement points to wettability by silica, perovskite lattice strain induced by the support, and curtailed quantities of secondary phases that limit accessibility to active surfaces. In this contribution, an appropriate stable platform for improving earth abundancy in perovskite-based redox materials is demonstrated for potential industrial-scale, low temperature CO₂ thermochemical conversion.