Betel nut wastes are firstly modified with nitric acid/thiourea to fabricate hetero-element doping carbon (C-H-T) for energy storage. C-H-T exhibits improved content of O (12.27%), N (2.52%), and S (2.88%) compared with that of purely carbonized carbon with O (9.2%) and N (1.76%). Without nitric acid heat treatment, the carbon materials prepared by hydrothermal treatment with thiourea only get increasing hetero-elements content of O (10.46%), N (2.9%), and S (0.53%). The similar results have been obtained using urea and melamine as dopants. Due to the synergistic effects of the hetero-elements containing functional groups, C-H-T get a significant enhancement in its electrochemical properties with a high capacitance (423 F g(-1) at 0.5 A g(-1)) in KOH electrolyte. C-H-T based coin-type symmetric supercapacitors display maximum energy density of 61.7 Wh kg(-1) and considerate cycling ability with 94% capacitance retention after 10 000 cycles. The fabricated two-step method can inspire the increase of hetero-elements content in carbon materials to develop its application in energy storage.