Waste to value added: Cu–Ni MOF catalyst synthesized from waste plastic for enhanced hydrogen generation and electrochemical energy storage

Abstract

This study presents the development of a copper-nickel metal–organic framework (MOF) for efficient hydrogen generation by catalytic alcoholysis of sodium borohydride. The organic linker, terephthalic acid, utilized in the MOF synthesis was obtained by depolymerizing discarded PET bottles (Cu–Ni–PET). For comparative analysis, another Cu–Ni MOF was developed using commercial terephthalic acid (Cu–Ni–C). Both MOFs were comprehensively characterized by employing FTIR, FESEM-EDS, TGA, XRD, XPS, HRTEM, and BET techniques to investigate their functional groups, morphologies, thermal stability, and crystalline structure. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to determine their energy storage potential. The Cu–Ni–PET MOF demonstrated a specific capacitance of 806 F/g, while the Cu–Ni–C MOF exhibited a specific capacitance of 766 F/g. Additionally, experiments were conducted to assess hydrogen generation using both catalysts. The maximum hydrogen generation rates for the Cu–Ni–PET MOF and Cu–Ni–C MOF were observed as 10,618.65 and 9695.29 ml/min/g catalyst, respectively, at 50 °C with 10 ml methanol, 0.25 g sodium borohydride, and 0.1 g catalyst. Furthermore, the ethanolysis of sodium borohydride was performed to quantify the produced hydrogen. Results indicated the production of 2650 and 2150 ml/min/g catalyst of hydrogen for the Cu–Ni–PET MOF and Cu–Ni–C MOF, respectively, at 50 °C with 10 ml ethanol, 0.25 g sodium borohydride, and 0.1 g catalyst. The development of the Cu–Ni–PET MOF provides an innovative solution for recycling PET waste and enhancing hydrogen generation efficiency.