Enhanced Electrosynthetic Hydrogen Evolution by Hydrogenases Embedded in a Redox-Active Hydrogel

Area of Science:

• Biotechnology
• Renewable Energy
• Electrochemistry

Background:

• Molecular hydrogen is a key energy carrier for future technologies.
• Hydrogenase enzymes offer efficient bioelectrochemical hydrogen production at ambient conditions.
• Efficient electron transfer to the enzyme's active site is crucial but often limited.

Purpose of the Study:

• To investigate the efficacy of a cobaltocene-functionalized polyallylamine (Cc-PAA) redox polymer for immobilizing hydrogenases.
• To evaluate the performance of immobilized hydrogenases in mediating rapid and efficient hydrogen evolution.
• To determine the electron transfer rates and efficiency of the Cc-PAA-mediated system.

Main Methods:

• Immobilization of three different hydrogenases (from Clostridium pasteurianum and Methanococcus maripaludis) onto a cathode using Cc-PAA redox polymer.
• Electrochemical analysis of hydrogen evolution activity.
• Measurement of faradaic efficiency and apparent overpotential.
• Comparison of enzyme activity in the Cc-PAA assay versus traditional methyl viologen assays.

Main Results:

• Cc-PAA successfully mediated rapid and efficient hydrogen evolution with immobilized hydrogenases.
• The system operated at high faradaic efficiency (80-100%) and low apparent overpotential (-0.578 to -0.593 V vs. SHE).
• Specific activities were comparable to traditional assays, indicating high-rate electron transfer by Cc-PAA to most embedded enzymes.

Conclusions:

• Cobaltocene-functionalized polyallylamine (Cc-PAA) is an effective redox polymer for immobilizing hydrogenases.
• The Cc-PAA system overcomes electron transfer limitations, enabling efficient bioelectrochemical hydrogen production.
• This approach represents a significant advancement for renewable hydrogen energy technologies.