In Situ Halogen-Ion Leaching Regulates Multiple Sites on Tandem Catalysts for Efficient CO 2 Electroreduction to C 2+ Products.

Tandem catalysts can divide the reaction into distinct steps by local multiple sites and thus are attractive to trigger CO 2 RR to C 2+ products. However, the evolution of catalysts generally exists during CO 2 RR, thus a closer investigation of the reconstitution, interplay, and active origin of dual components in tandem catalysts is warranted. Here, taking AgI-CuO as a conceptual tandem catalyst, we uncovered the interaction of two phases during the electrochemical reconstruction. Multiple operando techniques unraveled that in situ iodine ions leaching from AgI restrained the entire reduction of CuO to acquire stable active Cu 0 /Cu + species during the CO 2 RR. This way, the residual iodine species of the Ag matrix accelerated CO generation and iodine-induced Cu 0 /Cu + promotes C-C coupling. This self-adaptive dual-optimization endowed our catalysts with an excellent C 2+ Faradaic efficiency of 68.9 %. Material operando changes in this work offer a new approach for manipulating active species towards enhancing C 2+ products.