Ultralow-coordinated Ni species boosting paired electrosynthesis of formate from waste plastic and carbon dioxide

Paired electrolysis of waste feedstocks holds an energy-efficient alternative for chemical production; however, the sluggish anodic oxidation limited the total efficiency under larger current density. Herein, we constructed ultralow-coordinated Ni species with Ni–O coordination number of ∼3 via a hydrothermal synthesis-sulfidation-annealing process and electrochemical activation and demonstrated the vital role in accelerating the proton deintercalation and reactive oxygen intermediate ·OH formation during electro-reforming polyethylene terephthalate hydrolysate (POR). The target catalyst NiCoSx/NF afforded a high formate productivity of 7.4 mmol cm⁻² h⁻¹ at ∼600 mA cm⁻² with a formate Faradic efficiency (FE_formate) of 92.4% in POR and maintained a FE_formate of ∼90% for 100 h at 2 A in a membrane electrode assembly electrolyzer. Coupling POR on NiCoSx/NF with carbon dioxide reduction reaction on oxygen vacancies enriched Vo-BiSnO reached effective concurrent formate production with 172.7% of FE_formate at 500 mA cm⁻² and long-term stability. Such excellent performance shows the great prospect of electrocatalyst design by regulating the local metal environment.