Microwave-Driven Reduction Accelerates Oxygen Exchange in Perovskite Oxides

Abstract

Microwave-assisted oxide reduction has emerged as a promising method to electrify chemical looping processes for renewable hydrogen production. Moreover, these thermochemical cycles can be used for thermochemical air separation, electrifying the O2 generation by applying microwaves in the reduction step. This approach offers an alternative to conventional cryogenic air separation, producing pure streams of O2 and N2. The electrification by microwaves lowers the requirements for titanate perovskites (CaTi1−xMnxO3−δ), which typically demand high temperatures for thermochemical cycles. Microwave activation allows for a drastic reduction in the operation conditions of the reduction reaction, leading to unprecedentedly rapid absorption− desorption cycles (<3 min per cycle). For CaTi0.8Mn0.2O3−δ, we achieved a cycle-averaged O2 production of 2.6 mL g−1 min−1 at 800 °C, surpassing conventional values of materials operating in the high-temperature regime. This method could significantly impact thermochemical air separation by enabling a faster oxygen absorption−desorption cycle at more moderate temperatures than those of conventionally heated processes.