Upcycling Waste Polyethylene Terephthalate to Produce Nitrogen-Doped Porous Carbon for Enhanced Capacitive Deionization

Porous carbon with a high surface area and controllable pore size is needed for energy storage. It is still a significant challenge to produce porous carbon in an economical way. Nitrogen-doped porous carbon (N-PC) was prepared through carbonization of a mixture of waste PET-derived metal-organic frameworks (MOFs) and ammonium. The obtained N-PC exhibits a large surface area and controlled pore size. When utilized as an electrode material for supercapacitors, the N-PC exhibits a specific capacitance of 224 F g-1, significantly surpassing that of commercial activated carbon (AC), which has a capacitance of 111 F g-1. In the subsequent capacitive deionization (CDI) tests, the N-PC demonstrated a maximum salt adsorption capacity of 19.9 mg g-1 at 1.2 V in a NaCl electrolyte (0.5 g L-1), and the salt adsorption capacity increased to 24.7 mg g-1 at 1.4 V. The N-PC electrode also exhibited superior regeneration. The present work not only presents a potential approach to develop cost-effective electrodes for seawater purification but also paves the way for recycling of waste plastics into high value-added products.