Elucidating the Interactions between a [NiFe]-hydrogenase and Carbon Electrodes for Enhanced Bioelectrocatalysis

Abstract

Understanding the interactions and immobilization of hydrogenase on electrodes is important for promoting interfacial electron transfer and developing high-performance H2/O2 biofuel cells. The soluble hydrogenase I from the hyperthermophilic archaeon Pyrococcus furiosus (PfSHI) is a promising [NiFe]-hydrogenase. However, the [NiFe]-hydrogenase–electrode interface has not been explored on a microcosmic scale due to its structural complexity. In this work, an in-depth study of the interplay between PfSHI and carbon nanotubes was conducted via electrochemical techniques combined with a quartz crystal microbalance and modeling analysis. Through the interfacial analysis, it was found that PfSHI adopted different conformations on differently charged electrodes, demonstrating that electrostatic interaction may play the predominant role. Further, direct bioelectrocatalysis of H2 oxidation was investigated on different hydrophilic/hydrophobic electrode surfaces, and the results suggested that a hydrophobic interaction was another key factor determining the orientation distribution of PfSHI on the electrode. Reorientation occurred when PfSHI was close to the hydrophobic surface, leading to a proper spatial conformation on the electrode. Finally, a biofuel cell with immobilized PfSHI in a favorable orientation was constructed, exhibiting a superior power output at 60 °C 2-fold higher than that in a previous study. This study elucidates the absorption mechanism of PfSHI on functionalized electrodes, highlights the electrochemical methodology for analyzing the fundamentals of complex interfacial environments, and sheds light on the construction of high-performance bioelectrocatalytic interfaces.