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 (CaTi_1-xMn_xO_3-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 CaTi_0.8Mn_0.2O_3-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.