Hydrogenase-assisted catalysis on titania electrode oxides

The widespread use of fuel cells and water splitting devices for energy generation and storage is limited by the dependence on noble metal catalysts. There is thus a tremendous need for the development of efficient electrocatalysts based on Earth-abundant elements. Nature inspired hydrogenases (HydA) are metallo-enzymes that catalyze the reversible reaction of H₂ to protons and electrons. Hydrogenases containing Fe at the active sites, known as [FeFe]-HydA, show activities comparable to that of Pt. This work addresses a new class of electrodes for [FeFe]-HydA attachment and bio-assisted catalysis based on TiO₂ nanotubes. The conducting oxide material provides suitable electronic conduction and hydrophilicity, while the nanostructure ensures tunability (tube length, crystal orientation and pore diameter) and high surface area for HydA attachment. In this work, electron microscopy is used to characterize the bio-electrodes. Based on the experimental findings, density functional theory (DFT) calculations are used to probe the catalytic reaction sites on the HydA and address the interaction between enzymes and TiO₂. The novel bioelectrode will be employed in a system of artificial photosynthesis and generation of solar fuels by simultaneous water splitting and CO₂ capture and utilization.