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Highlights in Chemical Science

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Efficient hydrogen production is one step closer


12 December 2006

Japanese researchers have simplified and improved a common method for generating hydrogen gas, a potentially green energy source. 

The approach, developed by Shunichi Fukuzumi's group at Osaka University, is a modification of existing methods of hydrogen production where several reactions form a cycle, in which electrons are transferred from a readily available source to hydrogen ions. Fukuzumi's adapted method, which he describes as an important step for the use of hydrogen as a clean energy source, uses a molecule that combines two stages of the cycle. 

Usually, electrons from a donor molecule, such as ethanol, are supplied to a mediator that can pass them on to a molecule that has been activated by ultraviolet light. The light-activated molecule then supplies the electrons to the hydrogen ions in the presence of a platinum catalyst, generating hydrogen gas.

 

Photocatalytic hydrogen evolution system

 

Fukuzumi's method uses a molecule that plays the role of both the electron mediator and the light-activated species, transferring electrons from ethanol to the hydrogen ions. Their results show a significant increase in the efficiency of the process and the amount of hydrogen produced. 

Hydrogen gas is a promising green energy source because it produces only water when burnt, rather than climate-changing greenhouse gases; however, there remain several significant obstacles for the commercial production of hydrogen as an energy source. The discovery of a cheaper metal catalyst to replace the expensive platinum system would be beneficial, but the efficient transfer of electrons to the hydrogen ions is only half the story. 

Fukuzumi used nicotinamide adenine dinucleotide (NADH), an enzyme cofactor that plays a vital role in energy production in living cells, as the source of hydrogen ions. A method of generating hydrogen ions using just water and sunlight represents the next challenge for the future of hydrogen generation, said Fukuzumi.  

Paul O'Sullivan

References

Efficient photocatalytic hydrogen evolution without an electron mediator using a simple electron donor-acceptor dyad

H Kotani, T Ono, K Ohkubo, S Fukuzumi, Phys. Chem. Chem. Phys., 2007, 9

DOI: 10.1039/b612794k