Upcycling of plastic waste to atomic nickel site-decorated carbon for efficient electrochemical CO2 conversion

Abstract

Excessive CO₂ emission and plastic waste pollution constitute two pressing threats to our environment. Effective tactics are urgently demanded to address these issues. Herein, we report that the thermal treatment of plastic wastes in the presence of nickel chloride, melamine, and KCl/LiCl salt mixture produces atomic nickel and nitrogen-doped carbon materials (Ni–N–C), which are proven to be effective for electrocatalytic CO₂ conversion. We disclose that the treating temperature and the activation of molten KCl/LiCl play critical roles in fabricating Ni–N–C with high porosity, abundant Ni sites, and good charge transfer ability. As a result, Ni–N–C-800 prepared from polyethylene terephthalate bottles exhibits good performance in electrochemical CO₂-to-CO conversion. Importantly, a large current density of 400 mA cm⁻² and a high faradaic efficiency of 90% for CO production can be achieved in the flow cell, which endows Ni–N–C-800 with great prospects for industrial applications. Furthermore, we show that the thermal treatment of other plastic wastes such as polyethylene, polypropylene, and polyvinyl chloride can also yield effective Ni–N–C catalysts, demonstrating good universality of upcycling plastic wastes to efficient catalysts. This study puts forward a sustainable solution for the simultaneous valorization of both CO₂ and plastic wastes.