Biohybrid nanostructured ceria/glucose oxidase electrodes enabling enzyme glucose oxidation with pseudocapacitive charge buffering

Abstract

Biohybrid nanostructured electrodes that integrate redox enzymes with defect-engineered inorganic supports offer a promising route to couple bioelectrocatalysis with interfacial charge buffering. Here, nanostructured cerium oxide (CeO₂) films with tunable oxygen-vacancy concentrations were deposited by pulsed laser deposition under controlled atmospheres and subsequently functionalized with glucose oxidase (GOx) to form CeO₂/GOx electrodes. Control of the deposition environment enabled systematic tuning of ceria nanostructure, crystallinity, and Ce³⁺/Ce⁴⁺ ratios, as confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS further confirms enzyme immobilization through the presence of amide/amine nitrogen from the GOx backbone and heterocyclic nitrogen associated with the flavin adenine dinucleotide (FAD) cofactor, indicating preservation of the redox-active center at the ceria interface. Electrochemical measurements show that pristine CeO₂ films exhibit predominantly pseudocapacitive behavior and no measurable response toward glucose oxidation, whereas CeO₂/GOx electrodes display distinct catalytic redox features in the presence of glucose. The formal potential of the surface-confined redox couple is scan-rate independent and closely matches that of the FAD/FADH₂ couple, consistent with electronic communication between GOx and the ceria support. In addition to bioelectrocatalytic activity, CeO₂/GOx electrodes exhibit measurable charge-storage capability arising from the combined contribution of Ce³⁺/Ce⁴⁺ redox processes and reversible FAD cycling. These results demonstrate the feasibility of coupling enzymatic redox activity with pseudocapacitive charge buffering in oxide-based biohybrid electrodes, providing a versatile platform for future bioelectrochemical energy conversion and enzymatic biofuel cell applications.