Engineering Pt@β-Cyclodextrin/ZIF-8 Hybrid Thin Films: From Interfacial Surface-Enhanced Raman Spectroscopy to Enhanced Methanol Oxidation Performance in Fuel Cell

Abstract We report the design, synthesis, and electrocatalytic evaluation of two platinum-containing thin film catalysts for the methanol oxidation reaction (MOR): Pt@β-cyclodextrin (Pt@β-CD) and Pt@β-CD confined within zeolitic imidazolate framework-8 (Pt@β-CD/ZIF-8). Both materials were comprehensively characterized by FT-IR, SEM, XRD, Raman spectroscopy, TGA, BET, and AFM. Notably, Pt@β-CD exhibits a previously unreported Pt-induced surface-enhanced Raman scattering (SERS) signature: a broad doublet attributable to Raman-active β-CD-derived interfacial species (including oxidized CD products), supported by synthesis conditions and its suppression after ZIF-8 encapsulation. Zeta-potential measurements (≈ −58 mV) and combined spectroscopic evidence indicate a charge-transfer-mediated chemical enhancement mechanism tied to deprotonated β-CD surface species. Encapsulation in ZIF-8 yields a hybrid architecture that enhances methanol uptake and retention via β-CD host–guest interactions, promotes in situ ZIF-8 growth through – OH coordination to Zn2+, reduces particle aggregation, and improves wettability and pore accessibility. Electrochemical testing in acidic (Pt@β-CD) and alkaline (Pt@β-CD/ZIF-8) media shows that both catalysts deliver comparable peak current densities, onset potentials, Jf/Jb ratio, poisoning resistances, corrosion currents, mass activities, and specific power outputs, while the Pt@β-CD/ZIF-8 composite demonstrates superior performance due to stabilization and local methanol enrichment within the MOF network. These findings reveal a dual role for β-CD as a molecular stabilizer and surface-chemical modifier that both enables a unique Pt-mediated SERS response and improves MOR kinetics and stability when combined with ZIF-8 confinement.