Molecular modification enables CO electroreduction to methane on platinum surface in acidic media.

Cu-based materials can produce hydrocarbons in CO electroreduction (CORR), but their stability still needs to be enhanced particularly in acidic media. Metallic Pt is highly stable in both acidic and alkaline media, yet rarely utilized in CORR, due to the competitive activity in hydrogen evolution reaction (HER). In this research, abundant thionine (Th) molecules are stably confined within Pt nanocrystals via a molecular doping strategy. The Pt surface is successfully modulated by these Th molecules, and thereby the dominant HER activity is converted to CORR activity. CO could be electroreduced to CH using organic molecule-modified Pt-based catalysts for the first time. Specifically, this composite catalyst maintains more than 100-hour stability in strong acid conditions (pH 1), even comparable to those state-of-the-art CORR catalysts. spectroscopic analysis and theoretical calculations reveal that the molecular modification can decrease the energy barrier for *COOH formation, and guarantee the sufficient local *H near Pt surface. Additionally, the *H derived from HO dissociation is favorable for the *CO hydrogenation pathway towards *CHO, eventually leading to the formation of CH. This strategy might be easily applied to microenvironment and interface regulation in other electrocatalytic reactions.