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

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@In2 O3 @Bi50 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@In2 O3 @Bi50 catalyst can selectively reduce CO2 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/In2 O3 interfaces of core-shell C@In2 O3 @Bi will stabilize the key intermediate HCOO* and suppress CO poisoning, benefiting the CO2 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 CO2 conversion technology.