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

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.