Amine axial ligand-coordinated cobalt phthalocyanine-based catalyst for flow-type membraneless hydrogen peroxide fuel cell or enzymatic biofuel cell

In this study, an amine-coordinated cobalt phthalocyanine (CoPc)-based anodic catalyst was fabricated by a facile process, to enhance the performance of hydrogen peroxide fuel cells (HPFCs) and enzymatic biofuel cells (EBCs). For this purpose, polyethyleneimine (PEI) was added onto the reduced graphene oxide and CoPc composite (RGO/CoPc) to create abundant NH₂ axial ligand groups, for anchoring the Co core within the CoPc. Owing to the PEI addition, the onset potential of the hydrogen peroxide oxidation reaction was shifted by 0.13 V in the negative direction (0.02 V) and the current density was improved by 1.92 times (1.297 mA cm⁻²), compared to those for RGO/CoPc (0.15 V and 0.676 mA cm⁻², respectively), due to the formation of donor–acceptor dyads and the prevention of CoPc from leaching out. The biocatalyst using glucose oxidase (GOx) ([RGO/CoPc]/PEI/GOx) showed a better onset potential and catalytic activity (0.15 V and 318.7 μA cm⁻²) than comparable structures, as well as significantly improved operational durability and long-term stability. This is also attributed to PEI, which created a favorable microenvironment for the enzyme. The maximum power densities (MPDs) and open-circuit voltages (OCVs) obtained for HPFCs and EBCs using the suggested catalyst were 105.2 ± 1.3 μW cm⁻² (0.317 ± 0.003 V) and 25.4 ± 0.9 μW cm⁻² (0.283 ± 0.007 V), respectively. This shows that the amine axial ligand effectively improves the performance of the actual driving HPFCs and EBCs.