Catalytic Electrochemistry Of A [nifese]-hydrogenase On Tio_2 And Demonstration Of Its Suitability For Visible-light Driven H_2 Production

摘要

A [NiFeSe]-hydrogenase able to produce H_2 in the presence of O_2 forms the basis of a hybrid enzyme-TiO_2 nanoparticle system with a co-attached synthetic Ru photosensitiser for visible-light driven H_2 production at room temperature from neutral water under non-strictly anaerobic conditions on the bench.rnRenewable hydrogen is widely considered as a possible energy vector in the post-fossil fuel era, but there are major practical issues to resolve before a hydrogen economy becomes truly feasible, not least of which is the cheap and efficient production of H_2 from water, particularly using sunlight (artificial photosynthesis). From the physico-chemical angle, efforts have focused on Pt attached to semiconducting particles, but there is intense interest in identifying alternative catalysts, because Pt suffers from several drawbacks such as: (ⅰ) lack of selectivity (at low potentials it catalyses O_2 reduction at diffusion controlled rates), (ⅱ) poisoning by trace inhibitors (e.g., CO) which is difficult to reverse, and (ⅲ) high cost/limited resources, in particular considering large-scale applications.rnAn alternative approach is biological H_2 production by organisms expressing hydrogenases (H_2ases), which are iron-or ironickel-containing microbial enzymes that catalyse the reversible and selective interconversion of H_2 and 2H~+/2e~-. Here, there is a case for identifying H_2 producers among organisms that express [NiFe]-H_2ases rather than [FeFe]-H_2ases that are regarded as being more O_2 sensitive. We recently described studies of a [NiFeSe]-H_2ase (a subclass of [NiFe]-H_2ase containing a terminal selenocysteine coordinated to nickel at the [NiFe]-active site and three [4Fe4S]-clusters for intraprotein electron transfer) that is more active for H_2 production than normal [NiFe]-H_2ases yet should be able to function indefinitely in low levels of O_2. In this communication we have addressed this development in a practical context and demonstrate a rational photochemical H_2 cell that produces H_2 under visible light irradiation without resort to rigorous anaerobicity.