Identification of the surface chemical species of plasma-treated polytetrafluoroethylene by ab-initio calculations of the core-energy-level shift in X-ray photoelectron spectra

•F atoms in the plasma-treated PTFE were substituted by H atoms.•XPS and ToF-SIMS confirmed the existence of H on the plasma-treated PTFE surface.•The C1s binding energies are linearly dependent on the number of substituted F atoms.•Functional groups on fluoropolymers are identified using ab-initio calculation results.•Ab-initio calculation results reveal functional groups on fluoropolymers.