Engineering Bi‐Sn Interface in Bimetallic Aerogel with 3D Porous Structure for Highly Selective Electrocatalytic CO2 Reduction to HCOOH

Electrochemical reduction of CO 2 (CO 2 RR) into valuable hydrocarbons is appealing in alleviating the excessive CO 2 level. Herein, we present the very first utilization of metallic Bi-Sn aerogel for CO 2 RR with selective HCOOH production. Non-precious bimetallic aerogel of BiSn is readily prepared at ambient temperature which exhibits 3D morphology with interconnected channels, abundant interfaces and hydrophilic surface. Superior to Bi and Sn, the BiSn aerogel exposes more active sites and favorable mass transfer property and then endowing its high value of FE HCOOH with 93.9%. Moreover, the BiSn aerogel achieves FE HCOOH around 90% and maintained well for 10 h in a flow battery, indicating its potential applications in practical surrounding. In-situ ATR-FTIR measurement confirmed the formation of *HCOO is the rate-determining step toward formic acid generation. As a further evidence, DFT demonstrated the coexistence of Bi and Sn optimized the energy barrier for the production of HCOOH, and then yielding the improved catalytic activity.