Electroenzymatic cascade synthesis of 2,3-diaminophenazine on HRP-ZnGa2O4 nano-biohybrids

In this work, a novel nano-biohybrid has been developed for the efficient synthesis of 2,3-diaminophenazine (DAP), a biologically significant heterocyclic compound, via an electroenzymatic cascade catalysis system. Horseradish peroxidase (HRP) was integrated with high-surface-area zinc gallate (ZnGa₂O₄) nanoflowers. The ZnGa₂O₄ component serves dual functions as an effective immobilization support for HRP and as an electrocatalyst for the two-electron oxygen reduction reaction (2e⁻ORR) to generate hydrogen peroxide (H₂O₂) in situ. This in situ generated H₂O₂ directly activates the immobilized HRP, initiating the enzymatic oxidation of o-phenylenediamine (OPD) to DAP within the integrated nano-biohybrids. Capitalizing on nanoscale proximity, this architecture facilitates efficient channeling of H₂O₂ to the HRP active center and enables precise control over H₂O₂ yield through applied potential tuning, thereby matching enzymatic catalysis requirements. Consequently, this electroenzymatic cascade catalysis system achieves a 4.48-fold higher efficiency for DAP production compared to a conventional system relying on exogenous H₂O₂ addition, reaching 89.44% conversion of OPD in just 20 minutes. This work demonstrates the potential of coupling electrocatalysis and enzyme catalysis within integrated nano-biohybrids for developing highly efficient and controllable synthetic processes.