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

Abstract

In this work, a novel nano-biohybrid is developed for the efficient synthesis of 2,3-diaminophenazine (DAP), a biologically significant heterocyclic compound, via an electroenzymatic cascade catalysis. The horseradish peroxidase (HRP) is integrated with high-surface-area zinc gallate (ZnGa2O4) nanoflower. The ZnGa2O4 component serves a dual function 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-biohybrid. Capitalizing on nanoscale proximity, the 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 an 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.