Single-Atomic Ni-N₄ Biofuel Cell for Mimicking Intramolecular Electron-Harnessing of Laccase

Ni-N₄-PAN-NC, consisting of an atomic Ni-N₄ site, mimics the intramolecular electron-harnessing of natural laccase (LAC) confined in a zeolitic imidazolate framework-8 (LAC@ZIF-8) for anodic electrooxidation of bisphenol-A (BPA). We have introduced a facile π-conjugated unit of polyacrylonitrile (PAN)-resorcinol-derived N-doped conjugated -C≡N. The atomically dispersed Ni-single-atom in Ni-N₄ ^- PAN-NC exhibits high activity for the paired electrolysis of ORR and the electrooxidation of BPA with an enhanced current density. The single Ni-N_4-PAN-NC electrode effectively withdraws the electrons from electrooxidizing BPA due to a built-in electric field via incorporation of Ni-N₄. The paired electrolysis of Ni-N_4-PAN-NC biofuel cells is determined by LSV, EIS, and power-polarization curve for anodic electrooxidation of BPA. Machine learning molecular dynamics (ML-MD) simulation depicts non-covalent interaction (hydrogen bonding) between the O-hydroxyl of BPA and the N of the Ni-N_4-PAN-NC, suggesting preferential adsorption on the Ni-N_4-PAN-NC surface via weak van der Waals interactions and π-π stacking between the aromatic rings of BPA and the conjugated PAN-NC. An increased power density with increased concentration of BPA in the absence of ABTS suggests a DET mechanism of BPA electrooxidation on Ni-N₄, unlike a MET in the presence of ABTS when using LAC@ZIF-8. Thus, single atomic Ni - N₄ opens avenues with a DET mechanism.