An Artifical Leaf

Krishna Amin (St Catharine’s). November 16, 2019. 

Researchers from the Department of Chemistry announced a few weeks ago in Nature Materials the development of a new method of syngas production, paving the way for greener production practices.

Syngas is a crucial intermediate in the production of complex hydrocarbons, with applications extending to pharmaceuticals and fertilisers. The conventional reforming of methane to syngas is highly energy intensive and not always very efficient. Photoelectrochemical (PEC) production of syngas, a mixture of CO and H2, is an attractive green method of enabling a cyclical carbon economy. Current attempts, however, have been hindered by the high overpotential, low selectivity and cost of their catalysts.

The new method, proposed by Virgil Andrei, Bertrand Reuillard and Erwin Reisner, makes use of cobalt (II) meso-tetrakis(4-methoxyphenyl)porphyrin (CoMTPP), a molecular catalyst avoiding the sustainability question by using cobalt, a commonly available earth metal. CoMTPP is immobilised onto carbon nanotube (CNT) sheets (buckypaper), and the combination is employed in electrodes, perovskite-based photocathodes and perovskite-BiVO4 PEC tandem devices.

The result is tuneable syngas production through a tandem PEC device that reduces CO2 to CO through coupling to the oxidation of water to O2. Light intensity as low as 0.1sun still permits reduction, so that syngas could be produced during all day regardless of weather conditions, potentially answering the questions of economics and reliability that might hinder the development of this technology into a dominant source of hydrocarbon product.

Their paper:
Andrei, V., Reuillard, B. & Reisner, E. Bias-free solar syngas production by integrating a molecular cobalt catalyst with perovskite–BiVO4 tandems. Nat. Mater. 19, 189–194 (2020).

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