Iron-Poor Ferrites for Low Temperature CO₂ Conversion via Reverse Water-Gas Shift Thermochemical Looping

CO₂ utilization via the reverse-water-gas-shift (RWGS) reaction for the production of CO and then to long chain hydrocarbons is a potentially scalable method to mitigate rising global CO₂ emissions, if appreciable CO yields can be achieved at low reaction temperatures. Here, we report that Fe_0.35Ni_0.65O_xachieves, to the best of our knowledge, a record high experimentally measured CO yield of 80 mL-CO/g_MOx/cycle at low reaction temperatures (500°C for both oxidation and reduction steps) in a chemical looping (CL) process. This reported yield is an order of magnitude higher than previously reported RWGS-CL metal oxides at 500°C. We identified the composition of the metal oxide Fe_0.35Ni_0.65O_x using the Calculation of Phase Diagrams (CALPHAD) methodology to screen and filter through many combinations of metal oxides. We then experimentally tested this Fe_0.35Ni_0.65O_xmetal oxide for chemical looping RWGS and utilize x-ray characterization techniques and CALPHAD to find that a spinel-to-metallic phase transition gives Fe_0.35Ni_0.65O_x its noteworthy CO yield and oxygen capacity. We emphasize the importance of thermodynamics calculations and CALPHAD screening to quickly search through the vast design space of metal oxides to greatly reduce the amount of necessary experimentation.