Molecular modification enables CO₂ electroreduction to methane on platinum surface in acidic media

Cu-based materials can produce hydrocarbons in CO₂ electroreduction (CO₂RR), 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 CO₂RR, 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 CO₂RR activity. CO₂ could be electroreduced to CH₄ 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 CO₂RR catalysts. In-situ 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 H₂O dissociation is favorable for the *CO hydrogenation pathway towards *CHO, eventually leading to the formation of CH₄. This strategy might be easily applied to microenvironment and interface regulation in other electrocatalytic reactions.