Hybrid Co2Al-ABTS/reduced graphene oxide Layered Double Hydroxide: Towards O2 biocathode development

• Synthesis of new redox mediator intercalated Layered Double Hydroxide using the coprecipitation synthesis.
• Presence of electroactive Co into the LDH layers to enhance electroactivity of the system.
• Improvement of the electronic conductivity by association with reduced graphene oxide (GOr) into composite system.
• Application potentiality as biocathode material for O2 reduction with immobilization of Bilirubin Oxidase enzyme.
• Enhancement of the electrocatalytic response in the presence of a biopolymer like carrageenan into the electrode formulation

Co2Al-ABTS layered double hydroxides and associated Co2Al-ABTS@graphene composite were prepared in one pot technique by in situ coprecipitation. The as-obtained materials were then fully characterized by means of Powder X-Ray Diffraction, Fourier Transformed InfraRed and Scanning Electron Microscopy confirming the intercalation of azino-bis(3-ethylbenzothiazoline-6-sulphonate) (ABTS) between the LDH layers. Their electrochemical properties, according to Cyclic Voltammetry and Electrochemical Impedance Spectroscopy data, were improved compared to Zn2Al-ABTS reference material. Co2Al-ABTS hybrid LDH was found to combine both electronic transfers: interlayer provided by the presence of ABTS and intralayer due to the Co redox species. Moreover, an improvement of electronic transfer between the LDH particles was further achieved by addition of graphene. The resulting composite assemblies were tested for the first time as oxygen bioelectrode based on bilirubin oxidase. This original approach gives rise to enhanced electroenzymatic currents (×2.5) for oxygen reduction at 0 V and pH 7.0 as regard to that obtained for the reference laccase/LDH-ABTS based bioelectrode at pH 5.5.

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