Strategic PET Waste Upcycling: Converting Plastic into Power and Biodegradable Polymers

Researchers have successfully engineered a bifunctional catalyst using components derived directly from plastic waste to drive hydrogen production and electricity generation. This method integrates PET waste upcycling into a closed-loop energy system, effectively bypassing the high costs and instability inherent in traditional electrocatalysts.

The Bottleneck in PET Waste Upcycling

Polyethylene terephthalate (PET) constitutes a massive portion of global plastic refuse. While electrocatalysis presents a theoretical route to reprocess this material, current methodologies remain economically fragile. They depend heavily on expensive precious metals. They suffer from rapid deactivation. Consequently, scalability remains an unresolved challenge. The industrial sector requires a system that reduces input costs while maintaining stability under high current densities. Without reducing the reliance on virgin noble metals, the economics of recycling remain inverted.

Self-Sustaining Catalyst Design

The study introduces a 'full-molecule valorisation' strategy. Rather than discarding the benzene-1,4-dicarboxylate (BDC) obtained from PET hydrolysis, the team utilised it to construct the catalyst support itself. They synthesised a Platinum/Nickel-BDC (Pt/Ni-BDC) framework. This approach significantly lowers the requirement for noble metals by using the waste product as a functional structural component. The resulting material acts as a bifunctional electrode. It drives two distinct chemical processes simultaneously, turning a disposal problem into a resource.

Atomic-Level Efficiency

Mechanistic analysis indicates that the Ni-BDC framework enhances the adsorption of ethylene glycol (EG). Superior adsorption kinetics lead to faster reaction rates and greater stability. The performance metrics measured in the lab were distinct:

• EG Oxidation: Achieved a current density of 378.8 mA cm-2 at 1.0 V versus RHE.
• Selectivity: 90% conversion to glycolic acid (GA).
• Hydrogen Production: Required only 39.6 mV to reach 50 mA cm-2.

This performance exceeds that of commercial Platinum on Carbon (Pt/C) catalysts. The synergy between the recycled organic framework and the metal centres creates a highly active surface area, allowing the system to operate efficiently without excessive platinum loading.

From Waste to Watts

The utility extends beyond simple chemical conversion. The team deployed the catalyst in a membrane-free electrolyser. This device produced hydrogen continuously while oxidising EG at ampere-level currents. The glycolic acid produced was subsequently polymerised into polyglycolic acid (PGA), a valuable biodegradable plastic. Furthermore, an open-loop flow battery integrating this system generated electricity with an energy efficiency of 81%. This delivers a discharge capacity of 3.53 Ah L-1.

These results suggest a viable path for industrial facilities to treat plastic waste while generating their own power or feedstocks. Current methods often require expensive separation membranes and high energy inputs. This system operates membrane-free. It produces high-value PGA directly from the waste stream. The flow battery concept demonstrates that waste processing need not be an energy sink; it can be a source. By closing the loop, this technology could fundamentally alter the operational expenditure models for recycling centres.