Highly active and durable nanofiber-based fuel electrode with a hybrid structure for $CO_2$ electrolysis

Abstract

Leveraging the unique characteristics of nanofibers in the rational design of the fuel electrode microstructures offers a groundbreaking avenue to effectively utilize and maximize material properties, unlocking the potential for achieving highly efficient and sustainable $CO_2$ reduction reactions ($CO_2$RR) by solid oxide electrolysis cells (SOECs). However, the practical application of nanofiber-based electrodes is impeded by the inherent challenge of establishing sufficient interfacial contact and adhesion between porous nanofibers and the dense electrolyte. To address this challenge, we introduce a novel hybrid nanofiber electrode, $La_0.6Sr_0.4Co_0.15Fe_0.8Pd_0.05O_3-δ$ (H-LSCFP), by strategically incorporating low aspect ratio crushed LSCFP nanofibers into the excess porous interspace of a high aspect ratio LSCFP nanofiber framework synthesized via electrospinning technique. The LSCFP nanofibers undergo in-situ exsolution after consecutive treatment in 100% $H_2$ and $CO_2$ at 700 °C, leading to the formation of a perovskite phase with catalytically active metallic Co(majority) and Pd(minority) nanoparticles on the surface, as well as the formation of a high concentration of surface oxygen species, enhancing the $CO_2$ adsorption ability. The SOEC with the H-LSCFP electrode yielded an outstanding current density of 2.2 A $cm^-2$ in 100% $CO_2$ at 800 °C and 1.5 V, setting a new benchmark among reported nanofiber-based electrodes. Digital twinning of H-LSCFP at the electrode/electrolyte interface reveals that this hybrid structure simultaneously provides improved contact adhesion and an increased number of reaction sites available for $CO_2$RR. Our results demonstrate the feasibility of achieving a highly catalytically active and robust nanofiber-based fuel electrode with a hybrid structure, paving the way for further advancements and utilization of nanofibers in $CO_2$-SOEC applications.