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Sophisticated enzyme-mimic enables efficient hydrogen production

Date:
January 25, 2016
Source:
Universiteit van Amsterdam (UVA)
Summary:
Researchers have developed a new catalyst that paves the way for low-cost, large-scale hydrogen-production.
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At left the structure of the iron-iron hydrogenase active site. At right the synthetic mimic developed at the University of Amsterdam. The attached phosphole ligand (far right) acts as an electron reservoir, donating an electron to the active site during the catalytic cycle when needed.
Credit: HIMS

Researchers from the University of Amsterdam's Van 't Hoff Institute for Molecular Sciences (HIMS) have developed a new catalyst that paves the way for low-cost, large-scale hydrogen-production. The researchers, led by Professor Joost Reek, recently presented their enzyme-mimicking catalyst in Sciences Advances, the peer-reviewed open-access initiative of the publisher of Science.

A hydrogen-based sustainable economy depends on technology to generate molecular hydrogen using sustainable solar or wind energy. Catalytic chemistry already enables this by using water as feedstock and platinum and iridium as active materials. However, because such elements are scarce and expensive this technology cannot be applied at the required global scale.

Looking at nature

To overcome this hurdle, chemists have started looking toward nature where so-called iron-iron hydrogenase enzymes catalyse the conversion (reduction) of protons to molecular hydrogen with a performance comparable to platinum. It is a major challenge to apply these enzymes directly in hydrogen-producing devices since their isolation is difficult and their performance in air poor. Nevertheless, their high efficiency has spurred the search for comparable iron-based molecular complexes that also can produce hydrogen with a platinum-like performance.

Over the last decade, numerous synthetic complexes have been prepared that structurally and functionally mimic the active site of hydrogenase enzymes. Most of these 'synthetic hydrogenases' show serious drawbacks such as a low efficiency and stability and the requirement of organic solvents. Hydrogenase-mimics that perform efficiently in an aqueous environment while being tolerant to air have until now not been reported.

Characteristic feature

In the current edition of Science Advances, the researchers offer a possible solution by presenting a new oxygen-tolerant iron-iron hydrogenase-mimic that not only achieves efficient proton reduction in aqueous media but also displays electron storage and pre-organisation in close proximity to the active site -- a feature characteristic of working natural enzymes.

The Amsterdam-designed synthetic hydrogenase contains a redox-active phosphorous ligand that acts as an electron reservoir and actively partakes in the reduction of protons. It donates an electron to the active site during the catalytic cycle when needed. As a result, the catalyst displays high turnover numbers (TON) and turnover frequencies (TOF).

Combining this high performance with the operation in aqueous media and the tolerance towards oxygen, this new hydrogenase-mimic is a major step toward the development of catalysts for inexpensive large-scale hydrogen-producing devices. Further development will be directed toward analogs that operate at lower overpotentials and can be efficiently implemented in devices (for example, by anchoring to electrodes or metal-organic frameworks).


Story Source:

The above post is reprinted from materials provided by Universiteit van Amsterdam (UVA). Note: Materials may be edited for content and length.


Journal Reference:

  1. R. Becker, S. Amirjalayer, P. Li, S. Woutersen, J. N. H. Reek. An iron-iron hydrogenase mimic with appended electron reservoir for efficient proton reduction in aqueous media. Science Advances, 2016; 2 (1): e1501014 DOI: 10.1126/sciadv.1501014

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Universiteit van Amsterdam (UVA). "Sophisticated enzyme-mimic enables efficient hydrogen production." ScienceDaily. ScienceDaily, 25 January 2016. <www.sciencedaily.com/releases/2016/01/160125114924.htm>.
Universiteit van Amsterdam (UVA). (2016, January 25). Sophisticated enzyme-mimic enables efficient hydrogen production. ScienceDaily. Retrieved July 30, 2016 from www.sciencedaily.com/releases/2016/01/160125114924.htm
Universiteit van Amsterdam (UVA). "Sophisticated enzyme-mimic enables efficient hydrogen production." ScienceDaily. www.sciencedaily.com/releases/2016/01/160125114924.htm (accessed July 30, 2016).

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