Converting waste PET plastic into sulfonated carbon nanosheets supported PANI nanocomposite as anode catalyst in biophotovoltaic cells

Value-added graphitic carbon nanosheets are derived from waste polyethylene terephthalate (PET) plastic bottles via pyrolysis followed by sulfuric acid treatment. The resultant sulfonated carbon (S-gN) is composited with polyaniline (PANI), which shows excellent electrochemical performance and is employed as an anode catalyst in biophotovoltaic (BPV) cells. Morphological studies reveal PANI nanotubes covered in graphitic carbon nanosheets, and diffusion rings observed in the SAED patterns disclose the amorphous structure of S-gN/PANI. The XRD patterns of S-gN/PANI show the characteristic diffraction peaks of graphitic carbon and PANI, confirming composite formation. Furthermore, the presence of PANI and sulfonated carbon nanostructures is well supported by FTIR, EDAX, and X-ray photoelectron spectroscopy results. S-gN/PANI registered the maximum BPV power output of 11.8 mW m⁻² in the presence of Chlorella vulgaris corroborated by porous, surface active, and heterogeneous S-gN, facilitating an effective interaction with PANI nanotubes via electrostatic/π–π stacking. With these constructive interactions, PANI grown on S-gN provides more conduction channels, electrically conductive sites, and enriched catalytic active sites that enable access to the growth medium and facilitate sustainable electron transfer from microalgae to the electrode surface. The increasing microalgae growth enables healthy biofilm formation on S-gN/PANI/carbon cloth and promotes electron transfer from microalgae to the electrode, yielding excellent BPV output.