A 'Fluid' Nickel-Based Ferrite as an Efficient Redox Material for Thermochemical Two-Step CO <sub>2</sub> Splitting

Abstract

The solar-driven, thermochemical two-step CO2 splitting reaction is essentially hindered by sintering of the redox material, and thermostable supports are often employed to alleviate this issue, although they usually play a limited role due to the harsh thermal condition. Herein, we demonstrate a distinct strategy, by engineering a “fluid” nickel-based ferrite material without using any support. It maintains a steady-state CO yield over 20 cycles, which is up to three times higher than that of the traditional NiFe2O4/ZrO2 material. Characterizations and first principles calculations suggest that its superiority can be attributed to the significantly enhanced flow of Fe cations, dramatically different from the NiFe2O4/ZrO2, where the oxygen ion undertakes the major transport. Such cation diffusion mode in our novel ferrite material provides a more accessible path to the bulk reaction, leading to a fast bulk reaction kinetics in the ferrite. Thus, we developed a new approach to overcome the sintering problem of ferrite materials.