Hybrid Bioelectrocatalytic Reduction of Oxygen at Anthracene-modified Multi-walled Carbon Nanotubes Decorated with Ni90Pd10 Nanoparticles

Abstract

Considering the importance of the oxygen reduction reaction (ORR) for many energy conversion technologies, the design of cost-effective and active electrocatalysts is quite important for the future energy economy. In this investigation, we report the preparation of hybrid biocathodes containing multi-walled carbon nanotubes (MWCNTs) decorated with both enzymes and Ni90Pd10 metallic nanoparticles, targeting the bioelectrocatalytic reduction of oxygen in buffered solutions. The electrochemical characterization showed that the presence of the hydrophobic moieties did not affect the metal nanoparticle synthesis protocol, attesting to the possibility of obtaining a bifunctional material containing both the metallic nanoparticles and the aromatic moieties employed for enzyme orientation. Based on the electrochemical data obtained with the hybrid biocathodes, enhanced direct bioelectrocatalytic reduction of oxygen could be clearly observed at both laccase and bilirubin-based biocathodes, with a larger improvement for the hybrid bioelectrode prepared with laccase. In the laccase bioelectrode, the targeted reaction required a lower overpotential and provided about 50% higher current density, thus, demonstrating the benefit of incorporating small amounts of Ni90Pd10 metallic nanoparticles into enzymatic cathodes for the oxygen reduction reaction.