Polyethylene Terephthalate Waste-Derived Linker for Metal-Organic Framework-Based Cathode Catalyst in Microbial Electrolysis Cell for Hydrogen Production

Abstract

The microbial electrolysis cell (MEC) enables green biohydrogen production from waste through bioelectrochemical conversion, with a cathode catalyst driving hydrogen recovery. However, conventional cathode catalysts, such as platinum, are cost-intensive owing to expensive precursors and energy-intensive synthesis routes. Thus, in this investigation, terephthalic acid linkers derived from polyethylene terephthalate (PET) waste were employed to synthesize MIL-101 (Fe) and coated with MoS2 nanosheets to enhance active sites and hydrogen evolution in a single chamber MEC. The synthesis of the MIL-101 (Fe) and composite was verified through physicochemical characterization techniques, including scanning electron microscopy, which confirmed polyhedron and octahedral structures, and the Mo–S–Fe peak in X-ray photoelectron spectroscopy spectra, further reinforcing the anchoring of MoS2 over MIL-101 (Fe). Furthermore, electrochemical characterization confirmed the superior electrochemical activity of the MoS2-MIL-101 (Fe)-catalyzed cathode, with a low charge transfer resistance of 6.8 Ω and a peak current density of 33.7 A/m2. Moreover, the MEC with MoS2-MIL-101 (Fe) catalyst (MEC-M) achieved a maximum hydrogen production rate of 0.80 ± 0.03 m3/m3·d with a chemical oxygen demand removal of 74.85 ± 3.97%, while achieving cathodic hydrogen recovery of 75.74 ± 0.32% and energy recovery efficiency of 140.24 ± 0.58%, demonstrating efficient waste valorization and energy recovery. These findings demonstrate the feasibility of utilizing PET-derived linkers in metal-organic framework-based, low-cost cathode catalysts for hydrogen production through MEC.