Cathode tailoring of micro-tubular protonic ceramic electrochemical reactors for CO2 hydrogenation

Protonic ceramic electrochemical reactors (PCER), having the advantages of high efficiency, adjustability, and scalability, exhibit great potential in energy storage such as conversion of CO2 into high-value chemicals. Designing critical components like the electrolyte and electrodes of electrochemical reactors is essential to widen commercial applications. The present work constructed a three-layer microtubular PCER (MT-PCER) for CO2 hydrogenation. BaCe0.5Zr0.3Y0.2O3-δ (BCZY) was used as the electrolyte material to prepare BCZY/Ni-BCZY/Ni triple-layer hollow fibers (TLHFs) by a phase-inversion based co-spinning/co-sintering process. Porous Ni-BCZY was the catalytic functional (cathode) layer, and the metallic Ni composed the current collector layer. Results indicated that CO2 conversion and CH4 selectivity were significantly enhanced when the NiO content in the cathode layer increased from 40 % to 60 %, while there was no significant change for the content continuously increasing to 80 %. Compared with the reactor employing dual-layer hollow fibers, the Ni collector layer in TLHFs presented a remarkable intensification of the methanation performance. As a result, the MT-PCER with 60 % NiO content in the cathode layer and utilizing the Ni current collector was the recommended reactor structure, which possessed the CO2 conversion of 29.8 %, CH4 selectivity of 50.9 %, CH4 yield of 15.2 %, and faradaic efficiency of 43.6 % at 700 °C and 2 V applied voltage. The adjusted design of the TLHF facilitated the advancement of the performance and efficacy of the MT-PCER, promoting carbon capture, utilization, and storage processes.