Dicyanamide-Modified Platinum Enables Poisoning-Tolerant Nonaqueous Hydrogen Oxidation

Electrochemical devices operating under nonaqueous conditions are often limited by electrolyte decomposition and electrode poisoning during the hydrogen oxidation reaction (HOR). Here, polycrystalline platinum (Ptpoly) was electrochemically modified with the ionic liquid 1-methyl-3-propylimidazolium dicyanamide (MPIDCA) to create a selective interfacial layer that suppresses detrimental adsorption processes while retaining HOR activity. Physicochemical characterization and electrochemical analysis show that MPIDCA modification proceeds through the irreversible oxidation of dicyanamide species, producing a chemically heterogeneous surface containing MPI-, DCA-, and Pt–N-related species. Probe reactions reveal that the modified interface strongly suppresses surface-sensitive inner-sphere processes, including Pt oxide formation and the oxidation of ethanol and diglyme, indicating reduced accessibility of Pt sites to water, oxygenated adsorbates, anions, proton-carrier molecules, solvent molecules, and organic poisoning species. In contrast, ferrocene redox chemistry remains reversible and HOR proceeds on PtMPIDCA, demonstrating that the modified layer acts as a selective interfacial shield rather than a passivating film. In 0.5 M LiTFSI/Diglyme, PtMPIDCA requires lower potentials to reach the same HOR current densities and exhibits reduced hysteresis compared with unmodified Ptpoly. These improvements are consistent with a less poisoned Pt/electrolyte interface and increased tolerance toward trace-water-, anion-, solvent-, and impurity-related surface blocking. Overall, MPIDCA modification provides a molecular strategy for improving the poisoning tolerance of Pt during nonaqueous HOR, which is particularly relevant to lithium-mediated nitrogen reduction, where HOR can serve as a proton-regenerating anodic counter reaction.