Fast preparation of BiIn alloy membrane by joule heating for highly-efficient CO2 electroreduction

Carbon dioxide electroreduction, a green technology for artificial carbon cycle, is facing great challenges in designing efficient electrodes. The preliminary research mainly focused on electrodes assembled with powder catalysts and binders, which suffers from high interfacial resistance and insufficient exposure of active sites. Herein, a self-supporting BiIn alloy membrane with nano-thickness was grown in-situ on carbon paper by using the Joule-heating method. The millisecond temperature change (>6000 °C s −1 ) suppresses particles' coarsening and enables the membrane forming with high surface free energy, supplying optimal active sites with special electronic structure to promote CO 2 electroreduction to formic acid. In the H cell, the Faraday efficiency (FE) of formate reaches 100 % at −1.3 V vs the reversible hydrogen electrode. In a solid electrolyte cell, electrolyte-free formic acid was continuously produced for 120 h at −100 mA·cm −2 with FE higher than 90 %. In the alloy phase, the p -band centers of Bi and In were brought closer to their Fermi energy levels strengthen the adsorption of intermediate *OCHO and reduce the energy barrier of HCOOH formation. This work provides a new idea to fabricate binder-free electrodes with three-dimensional conductive skeleton for advanced electrochemical synthesis.