Theoretical Modeling, Facile Fabrication, and Experimental Study of Optimally Bound Bilirubin Oxidase on Palladium Nanoparticles for Enhanced Oxygen Reduction Reaction

This paper presents an optimally bound bilirubin oxidase (BOD) (Myrothecium verrucaria) on palladium nanoparticles (Pd NPs) for enhanced oxygen reduction reaction (ORR). Theoretical modeling of BOD on Pd demonstrated that Pd has strong preferential binding to BOD via T1 copper (Cu) site because of its high adsorption energy. This preferential binding was accompanied by a reduction in distance between the Cu active sites and Pd which would result in an increase in electron transfer rate (k_cat) and an enhancement in catalytic activity of BOD. Inspired by the computational results, a biocathode comprising carbon nanotube (CNT), Pd NPs, and BOD (CNT-Pd-BOD) was facilely fabricated using an electroless deposition method. The CNT-Pd-BOD biocathode exhibited higher catalytic activity (1.52 times) and k_cat (1.71 times) when compared with CNT-BOD only biocathode. These results demonstrate Pd NPs as a suitable substrate for preferential binding with BOD to increase catalytic activity.