Revealing the Fundamental Origin of the CO-Free Pathway Selectivity in Alkaline Methanol Electrooxidation on Bi-Modified Pt

A long-standing puzzle for methanol electrooxidation is the fundamental understanding of the origin of electrocatalytic selectivity. Herein, we unequivocally demonstrate that the Bi-modified Pt/C follows a CO-free dominated pathway during alkaline methanol electrooxidation and unveil the formaldehyde (HCHO) intermediate as a critical factor influencing pathway selectivity. These findings are substantiated by kinetic isotope effects, formate Faradaic efficiency, in situ spectroscopy, ab initio molecular dynamics simulations, and density functional theory calculations. Bi modification significantly increases the HCHO dehydrogenation barrier, which facilitates its desorption and subsequent conversion to the H2COOH– anion at the alkaline interface, intrinsically avoiding CO formation. More specifically, the formation of ensemble sites featuring a V-shaped Bi–Pt–Bi configuration inhibits the cleavage of the C–H bond, and the weak OH binding energy at Bi adatoms effectively prevents blockage of oxygenated species, allowing such ensemble sites to fulfill their functional role. This work provides in-depth insights into the origins of pathway selectivity and benefits the theory-guided design of advanced CO-free electrocatalysts.