Recycling of end-of-life solar panels: Focusing on the pyrolysis conversion of back sheet from a micro perspective

Abstract

© 2025 Elsevier LtdThe accelerated deployment of solar photovoltaic (PV) systems will inevitably result in an increasing volume of end-of-life PV panels, which will pose significant environmental challenges and could potentially hinder the growth of renewable energy systems. This study provided a comprehensive examination of the pyrolysis behavior, kinetics, thermodynamics, and evolved products of typical back sheet PVDF/PET/fluorine film (KPF). In addition, an analysis of the enthalpy-entropy compensation (EEC) was performed. Reactive force field molecular dynamics (ReaxFF-MD) simulations were employed to identify atomic-level intermediates and investigate the reaction pathway. The decomposition of KPF sample occurred in three stages, characterized by temperature ranges of below 473.15 K, 473.15–923.15 K, and 923.15–1173.15 K. The corresponding mass losses were found to be 0.61–0.90, 78.30–82.06, and 1.38–2.56 wt%, respectively. The predominant products identified included benzoic acid and its derivatives, which corroborated the strong presence of the C=O group in the FTIR analysis. ReaxFF-MD simulations revealed the formation of C7H4O2, C7H4O and C7H5O2 species, and the decomposition process was found to involve random scission, decarboxylation and decarbonylation reactions. Activation energies from the FWO, KAS, and Friedman methods exhibited a declining trend, decreasing from 72.12 to 40.92 kJ mol−1. The master-plot analysis indicated that the P2 mechanism provided a more accurate description of KPF pyrolysis. The positive ΔH and ΔG values confirmed that KPF decomposition was an endothermic and non-spontaneous process. The ΔH-ΔS relationship indicated the presence of an EEC, with a compensation temperature of 687.49 K and an experimental temperature of 766.60 K.

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