Ultrasound-driven formation of defects and radicals in contact-electro-catalysis: a DFT and AIMD investigation

• Ultrasonic treatment induces significant physical changes on the FEP surface. • Sonochemistry induces molecular changes in FEP, particularly in C–H bond. • The fluoride concentration in water significantly increased after sonication of FEP. • Mechanistic framework was established to clarify ambiguities in ultrasound-CEC. This study reveals the critical chemical and physical roles of ultrasound in enhancing contact-electro-catalysis (CEC), using the methane (CH 4 ) oxidation process as a model system. By integrating density functional theory (DFT), ab initio molecular dynamics (AIMD), and targeted experiments, we demonstrate for the first time that ultrasonic treatment significantly modifies the solid material’s (i.e. CEC catalyst) surface chemistry and morphology, leading to enhanced catalytic performance. FTIR and Raman spectroscopy analyses reveal distinct molecular-level changes in the tested solid material (i.e. fluorinated ethylene propylene (FEP)) following ultrasonication, specifically the formation of C–H bonds, aligning closely with theoretical spectra predictions. Additionally, ultrasound induces substantial physical alterations, tripling the surface roughness of FEP, and significantly elevating fluoride ion concentrations in the surrounding solution, indicating pronounced C–F bond cleavage. AIMD simulations further elucidate that ultrasound-generated radicals initiate homogenous catalytic pathways by cleaving C–H bonds in CH 4 , identifying this as a critical mechanistic step previously unclarified. Those induced structural defects in FEP could also simultaneously enhance heterogeneous catalytic activity. Our findings establish a comprehensive mechanistic framework that resolves prior ambiguities in ultrasound-assisted CEC processes, offering robust theoretical and experimental foundations for advancing CEC catalytic efficiency and guiding future CEC catalyst development.