A pure non-metallic catalyst, the nitrogen doped hydrothermal carbon (NHCs) which can be comparable to zero-valence-iron, was designed for activation of PMS and PDS assisted by ultrasonic-mechanochemical action. NHCs were prepared via hydrothermal and heat treatments with N sources (melamine derived carbon nitride) and C sources (glucose derived hydrothermal carbon), and the range of preparation temperature of efficacious NHCs was around 400–800 °C. The excess N source (carbon nitride/glucose at 2.00 g/0.50 g) can observably improve the activation ability of NHCs. Especially, the optimal NHCs under ultrasonic driving showed efficient catalytic capability for PMS, 10 mg NHCs could effectively activate 0.75 mmol (≈ 0.25 g) PMS (the ratio at 1:25) for > 90 % removal of contaminant within 10 min (kapp = 0.3653 min−1). Mono- and dual-persulfates (peroxymonosulfate (PMS) and peroxydisulfate (PDS)) with different reactivities led to different reaction mechanisms in metal-free carbo-catalysis driven by the physical field. The NHCs particles could change the ultrasonic-field propagation. Afterwards, besides non-radical process (e.g., singlet oxygen (1O2)), 10−2 g/L level NHCs served as the electron shuttle (ES) to place emphasis on electron-transfer process (ETP) in activating PMS while 10−1 g/L level NHCs showed forced adsorption balance and tended to form persistent free radicals (PFRs) in activating PDS due to the ultrasonic mechanochemical action. This study supplements insightful understanding of the differences in metal-free activation, namely, NHCs materials without metal ion pollution toward PMS and PDS activation for water purification.