Utilization of Poly(Ethylene Terephthalate) Waste Bottle into Disodium Terephthalate: A Sustainable Electrolyte for Visible to Near‐Infrared Broadband Electrochromic Modulation

Abstract The growing challenge of poly(ethylene terephthalate) (PET) plastic bottle waste underscores the urgent need for innovative solutions. This study introduces a pioneering approach to repurpose PET waste into valuable electrolytic material for electrochromic (EC) smart windows, presenting a novel strategy to address environmental concerns while advancing technology. Through alkaline depolymerization, disodium terephthalate (DST) electrolyte is derived from PET waste, offering an eco‐friendly and cost‐effective alternative. Integrated with chromogens such as 1‐hexyl‐[4,4′‐bipyridin]‐1‐ium iodide [MV(I)], or 1,1′‐dihexyl‐[4,4′‐bipyridine]‐1,1′‐diium iodide [DVH(I)], or 1,1′‐dihexyl‐[4,4′‐bipyridine]‐1,1′‐diium dihexafluorophosphate [DVH(PF 6 )], alongside hydroquinone [HQ] and poly(ethyene glycol) diacrylate [PEGDA]: water, novel EC gel‐based devices are fabricated. Notably, ED‐3 exhibits dual‐band absorption across the visible to near‐infrared spectrum, enabling seamless color transitions and exceptional optical contrast. With (ΔT) values of 88.03% at 550 nm and 73.7% at 900 nm, along with a coloration efficiency of 277 cm 2 C⁻¹ and cyclic stability exceeding 2000 cycles, this innovative approach marks a significant advancement in PET waste upcycling for EC applications. Furthermore, this research contributes to addressing the global challenges of plastic waste pollution and energy consumption, underscoring the transformative potential of sustainable material development.