Pd-Based Metal Aerogels with Promoted Bioelectrocatalytic Behavior

Aerogels derived from noble metal nanoparticles (NPs) are a new kind of metal materials, which combine the nano-sized scale with that of materials of macro dimensions.[1] These metal aerogels are expected to provide a matrix with high electrical conductivity and high surface area for electrochemical applications. They may also offer inherent catalytic activity and generally fast (reversible) electron-transfer kinetics. In that respect, enzyme-loaded metallic aerogels in combination with their meso/macroporous structure can facilitate electron and mass transfer processes, which are both important for bioelectronic applications, e.g., in electrochemical biosensors and in biofuel cells.[2]

  Here the controlled growth of Pd aerogels has been facilely realized by using calcium ions as the destabilizing agent. The involving Pd aerogels with different porosities and surface areas exhibited faster electrode kinetics and higher activities towards the bioelectrooxidation of glucose when co-immobilized with glucose oxidase (GOD), compared to the Pd NPs and glassy carbon.[3] Based on the Pd aerogels promoted bioelectrocatalysis, we have developed a newly designed metal aerogel-based biofuel cell system. In the text, a commonly used mediator, ferrocenecarboxylic acid (Fc), was integrated into the Pd hydrogel and thus produced a Pd-Fc composite aerogel mediator for GOD at the bioanode. Additionally, bilirubin oxidase (BOD) encapsulated into a Pd-Pt alloy aerogel played a synergetic role towards the reduction of O₂, which promoted the direct electrocatalytic reduction of O₂ at the biocathode with an onset potential of 0.56 V under neutral conditions. By employing these two bioelectrodes, the assembled membrane-less glucose/O₂ biofuel cell showed a maximum power output of 20 μW cm^-2 at 0.25 V.[4,5] 

References

[1] N. Gaponik, A.-K. Herrmann, A. Eychmüller, J. Phys. Chem. Lett. 2012, 3, 8–17.

[2] Gao, F.; Viry, L.; Maugey, M.; Poulin, P.; Mano, N. Nat. Commun. 2010, 1, 2.

[3] D. Wen, A.-K. Herrmann, L. Borchardt, F. Simon, W. Liu, S. Kaskel, A. Eychmüller, J. Am. Chem. Soc. 2014, 136, 2727–2730.

[4] W. Liu, P. Rodriguez, L. Borchardt, A. Foelske, J. Yuan, A.-K. Herrmann, D. Geiger, Z. Zheng, S. Kaskel, N. Gaponik, R. Kötz, T. Schmidt, A. Eychmüller, Angew. Chem., Int. Ed. 2013, 52, 9849–9852.

[5] D. Wen, W. Liu, A.-K. Herrmann, A. Eychmüller, Chem. Eur. J. 2014, 20, 4380–4385.