Synthesis of chromium carbide from waste polytetrafluoroethylene under mild conditions

Abstract In this study, highly crystalline orthorhombic chromium carbide (Cr 7 C 3 ) nanoparticles were synthesized via a lithium thermal reduction route under mild conditions. The reaction was conducted in a stainless steel autoclave at 500 °C, using chromium sesquioxide (Cr 2 O 3 ), metallic lithium, and waste polytetrafluoroethylene (PTFE) as raw materials. When Cr 2 O 3 was replaced with other chromium sources, such as chromium trioxide (CrO 3 ), potassium dichromate (K 2 Cr 2 O 7 ), or ammonium dichromate ((NH 4 ) 2 Cr 2 O 7 ), Cr 7 C 3 could also be obtained through a similar procedure. This demonstrates a general and convenient approach for synthesizing crystalline Cr 7 C 3 using waste PTFE as a carbon source. This method not only provides a novel low-temperature route for Cr 7 C 3 preparation but also offers a sustainable strategy for recycling waste plastics.