Promotion of CO2-to-formate conversion via fluorine modification on amorphous indium hydroxides

An electrochemically-driven fluorine-erosion mechanism was proposed. • Active F species from GDL was generated during CO 2 RR through the mechanism. • Active F eroded the amorphous In hydroxides keeping high valence state for In. • In with high valance state facilitated CO 2 adsorption, promoting CO 2 RR. • High FE (93%) and partial current density (648 mA cm −2 ) of formate were achieved. Amorphous catalysts feature highly defective structures, providing more potential active site for electrochemical CO 2 reduction reaction (CO 2 RR). However, amorphous structures that lack control often lead to excessive side reactions and unforeseen structural reconstruction, largely suppressing the electroactivity. This study builds upon our earlier strategy relative to fluorine erosion, further elucidating an electrochemically-driven fluorine-erosion mechanism. Specifically, reactive fluorine species generated via the reversible electroreduction of polytetrafluoroethylene from the gas diffusion layer can effectively fluorinate amorphous indium hydroxides under CO 2 RR conditions, thereby creating active indium-fluorine content. This process enables the indium species to maintain a high valence state under electroreduction. Theoretical calculations demonstrate that fluorine-induced indium species facilitate CO 2 adsorption, promoting CO 2 RR pathway and subsequent formate production. The enhanced CO 2 RR performance can reach an impressive Faradaic efficiency of 93% at the partial current density of 648 mA cm −2 toward formate. This work sheds light on a novel approach for the structural control and modification for amorphous catalysts, highlighting a novel mechanism for fluorine erosion from the gas diffusion layer during electrocatalysis. Download: Download high-res image (244KB) Download: Download full-size image