Cobalt phosphide decorated on nickel foam as an efficient electrocatalyst for oxygen evolution, ethylene glycol oxidation, and polyethylene terephthalate plastic waste upcycling

The integration of oxygen evolution reaction (OER) with thermodynamically favorable anodic oxidation reactions provides a sustainable alternative for electrochemical valorization. Here, cobalt phosphide (CoP) nanoparticles are decorated on nickel foam (NF) and used as an electrocatalyst through a simple two-step hydrothermal decomposition and drop-casting process. The CoP/NF electrocatalyst demonstrated outstanding OER performance, with an overpotential of 250 mV and a Tafel slope of 136 mV dec⁻¹. Additionally, the developed CoP/NF electrode as an anode exhibits excellent electrochemical oxidation performance for ethylene glycol oxidation (EGOR) and for the electrolysis of polyethylene terephthalate (PET) to produce formate. The superior performance in formate production can be attributed to the high electron mobility and low charge-transfer resistance of the CoP/NF toward PET. Meanwhile, the cathode undergoes a hydrogen evolution reaction to produce H₂. It was found that longer electrolysis times can lead to greater formation. The as-constructed CoP/NF showed a significant decrease in anodic potential of 1.23 V vs RHE during EGOR compared to 1.48 V for OER at 10 mA cm⁻². Furthermore, the CoP/NF achieved an excellent overpotential of 1.33 V for the PET electrooxidation into formate. Notably, an energy-efficient pair-electrolysis system coupling HER and EGOR was used with the developed CoP/NF electrocatalyst in PET plastic hydrolysate to produce H₂ and chemicals simultaneously. Our work highlights the potential of CoP nanoparticles as an advanced electrocatalyst for the electrochemical reforming of abundant PET waste into valorization chemicals.