Co-hydrothermal carbonization of polyvinyl chloride and shrimp shells for carbon materials: Synergistic conversion and electrochemical properties

Plastic and biomass waste are high quality carbon sources for carbon materials. Polyvinyl chloride (PVC) and shrimp shells were selected to investigate the synergistic conversion of co-hydrothermal carbonization and the electrochemical properties of carbon materials. It was found that the particle agglomeration of PVC plastics could be effectively avoided, thus, the dechlorination from UPVC tubes and shrimp shells at 220 °C for 120 min (HUPS 220–120) was up to 100.9 wt%, which was four times higher than solo hydrothermal treatment of UPVC tubes. The dissolution of calcium and magnesium in PVC plastics or shrimp shells was positively and linearly related to the removal of chloride ions on PVC plastics, with the molar ratio close to 1:2. The hydrolysis of shrimp shells catalyzed by hydrogen chloride (HCl), providing abundant nucleophilic groups, which in turn substituted for chlorine on PVC to form polyethers and polyamines. Interestingly, the co-hydrothermal treatment induced O and N functional groups on the hydrochars to maintain and evolve into C O and pyridinic-N after further carbonization and activation. With the features of large specific surface (1161.3 m 2 ·g −1 ), numerous microporous (87.66 %), high graphitization degree (I D /I G =0.85), and abundant C O and pyridinic-N, the carbon materials derived from hydrochar (CHPS 220–60) demonstrated strong charge storage capacity, good conductivity, and multiple redox potentials, raising the capacitive performance as high as 277.5 F·g −1 at 0.5 A·g −1 . This work aims to provide an effective method not only for the upcycling of PVC plastics and shrimp shells but also for the preparation of energy storage materials.