Recycling plastic waste into nitrogen plasma-enriched polyethylene terephthalate@aluminum oxide counter electrodes...

Recycling plastic waste into functional energy materials remains both an urgent challenge and a transformative opportunity for sustainable development. In this work, we report for the first time the fabrication of nitrogen plasma-enriched PET@Al₂O₃ (N-PET@Al₂O₃) CEs, derived from recycled PET waste, for application in DSSCs. PET@Al₂O₃ composites were exposed to nitrogen plasma for controlled durations (0-4 min), yielding samples NPA0-NPA4, to systematically evaluate the effect of plasma treatment on their electrocatalytic behavior, interfacial chemistry, and photovoltaic performance. Interestingly, plasma activation induced pronounced microstructural evolution, with surface roughness nearly doubling (4.7 → 9.5 μm) and porosity rising markedly (14 % → 25 %), thereby enhancing catalytic accessibility and electrolyte infiltration. Correspondingly, these modifications induced band-gap narrowing, enhanced electrical conductivity, and a transition from hydrophobic to strongly hydrophilic surfaces, collectively strengthening adhesion and promoting more robust electrolyte-electrode interactions. Electrochemical characterizations confirmed that R_ct decreased sharply from 80 Ω (NPA0) to 15 Ω (NPA4), translating into a remarkable increase in photovoltaic efficiency from 3.49 % to 8.97 %. IPCE values reached ∼85 %, approaching the Pt benchmark (∼90 %). Overall, the optimized NPA4 delivered ∼94 % of Pt's performance while retaining significant advantages in sustainability and cost-effectiveness. The findings highlight nitrogen plasma treatment as an effective upcycling pathway that converts plastic waste into efficient and economical counter electrodes, creating a direct link between waste valorization and sustainable energy technologies. Beyond DSSCs, this scalable and green methodology provides a versatile and broadly adaptable platform for engineering next-generation electrodes from diverse polymeric wastes and dopant systems, underscoring its broad relevance for clean energy and circular economy technologies.