Solar-assisted two-stage catalytic membrane reactor for coupling CO₂ splitting with methane oxidation reaction

A two-stage catalytic membrane reactor (CMR) that couples CO₂ splitting with methane oxidation reactions was constructed based on an oxygen-permeable perovskite asymmetric membrane. The asymmetric membrane comprises a dense SrFe_0.9Ta_0.1O_3-δ (SFT) separation layer and a porous Sr_0.9(Fe_0.9Ta_0.1)_0.9Cu_0.1O_3-δ (SFTC) catalytic layer. In the first stage reactor, a CO₂ splitting reaction (CDS: 2CO₂ → 2CO + O₂) occurs at the SFTC catalytic layer. Subsequently, the O₂ product is selectively extracted through the SFT separation layer to the permeated side for the methane combustion reaction (MCR), which provides an extremely low oxygen partial pressure to enhance the oxygen extraction. In the second stage, a Sr_0.9(Fe_0.9Ta_0.1)_0.9Ni_0.1O_3-δ (SFTN) catalyst is employed to reform the products derived from MCR. The two-stage CMR design results in a remarkable 35.4% CO₂ conversion for CDS at 900 °C. The two-stage CMR was extended to a hollow fiber configuration combining with solar irradiation. The solar-assisted two-stage CMR can operate stably for over 50 h with a high hydrogen yield of 18.1 mL min⁻¹ cm⁻². These results provide a novel strategy for reducing CO₂ emissions, suggesting potential avenues for the design of the high-performance CMRs and catalysts based on perovskite oxides in the future.