In the process of radiation therapy (RT), the cytotoxic effects of excited electrons generated from water radiolysis tend to be underestimated due to multiple biochemical factors, particularly the recombination between electrons and hydroxyl radicals (·OH). To take better advantage of radiolytic electrons, we constructed WO3nanocapacitors that reversibly charge and discharge electrons to regulate electron transportation and utilization. During radiolysis, WO3nanocapacitors could contain the generated electrons that block electron-·OH recombination and contribute to the yield of ·OH at a high level. These contained electrons could be discharged from WO3nanocapacitors after radiolysis, resulting in the consumption of cytosolic NAD+and impairment of NAD+-dependent DNA repair. Overall, this strategy of nanocapacitor-based radiosensitization improves the radiotherapeutic effects by increasing the utilization of radiolytic electrons and ·OH, warranting further validation in multiple tumour models and preclinical experiments.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12951-023-01962-8.