The production of fuel from sunlight and water via photochemical energy conversion provides sustainable methods for producing clean energy. In particular, H2 gas is a promising fuel alternative that can be used to produce clean energy without generating environmental pollution. Here, we report on a de novo-designed artificial hydrogenase (ArH) where two cysteine (Cys) residues are introduced at tandem a/d positions of a heptad to generate a tetrathiolato Ni binding site. The artifical hydrogenase (ArH) is a photochemical producer of H2 and demonstrates a bell-shaped pH activity profile. Nanosecond transient absorption spectroscopy (nsTAS) is used to probe the Ru(I) intermediate generated in situ from the photocatalytic hydrogen evolution system using Ru(bpy)32+ (RuII) as the photosensitizer and ascorbic acid (H2A) as a sacrificial electron donor (SED). pH dependent nsTAS studies reveal production of the reduced RuI intermediate is limited by the reduction ability of the SED and that activity is also limited by the protonation of NiII-H- by H+ on the Cys.

Mechanistic insights related to photocatalytic H2 production from a de novo-designed artificial metallopeptide hydrogenase

ACS Fall 2021

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