One‐Step Phase Separation for Core‐Shell Carbon@Indium Oxide@Bismuth Microspheres with Enhanced Activity for CO2 Electroreduction to Formate

Abstract It is a substantial challenge to construct electrocatalysts with high activity, good selectivity, and long‐term stability for electrocatalytic reduction of carbon dioxide to formic acid. Herein, bismuth and indium species are innovatively integrated into a uniform heterogeneous spherical structure by a neoteric quasi‐microemulsion method, and a novel C@In 2 O 3 @Bi 50 core‐shell structure is constructed through a subsequent one‐step phase separation strategy due to melting point difference and Kirkendall effect with the nano‐limiting effect of the carbon structure. This core‐shell C@In 2 O 3 @Bi 50 catalyst can selectively reduce CO 2 to formate with high selectivity (≈90% faradaic efficiency), large partial current density (24.53 mA cm −2 at −1.36 V), and long‐term stability (up to 14.5 h), superior to most of the Bi‐based catalysts. The hybrid Bi/In 2 O 3 interfaces of core‐shell C@In 2 O 3 @Bi will stabilize the key intermediate HCOO* and suppress CO poisoning, benefiting the CO 2 RR selectivity and stability, while the internal cavity of core‐shell structure will improve the reaction kinetics because of the large specific surface area and the enhancement of ion shuttle and electron transfer. Furthermore, the nano‐limited domain effect of outmost carbon prevent active components from oxidation and agglomeration, helpful for stabilizing the catalyst. This work offers valuable insights into core‐shell structure engineering to promote practical CO 2 conversion technology.