Hydrogen is a highly efficient energy carrier that can be used to transport, store and provide energy. The gas, which consists of two hydrogen atoms, can be produced from many different energy sources. The problem with today’s production is that about 95 percent is created from fossil fuels, such as natural gas, which contributes to high carbon dioxide emissions. Alternative production methods are being developed, especially those involving the decomposition of water, processes which, however, require large amounts of electricity. But in a new study, published in the scientific journal Chemical Communications, a team of researchers in Lund has succeeded in finding a method that could enable fossil-free production of hydrogen on a large scale.

“For the first time, we have succeeded in using an iron complex as a light-absorbing dye for a hydrogen-producing catalyst. The solution was to excite an electron using an iron complex and light,” says Kenneth Wärnmark, a chemistry researcher at Lund University.

Iron produces more hydrogen

In the past, so-called photocatalytic hydrogen systems have worked best if the light-catcher has been a noble metal such as ruthenium or iridium, metals that are both rare and expensive. The fact that a base metal such as iron can be effectively used as a light-trapping agent did not come as a total surprise to the research team, who have previously used similar iron complexes as light-trapping agents in solar cells.

“In the iron case, the hydrogen is produced more slowly than in the ruthenium case, but the iron-based light trap is stable for a longer time and produces more hydrogen in the long run,” says Kenneth Wärnmark.

Can replace batteries

Hydrogen could be used in internal combustion engines, with water as the only emission. The gas is already being used in fuel cells to produce electricity that can power electric cars, for example. Recently, it has been shown that hydrogen can be used to make steel instead of coke. This means that ten percent of Sweden’s carbon dioxide emissions could be eliminated if the hydrogen were produced without fossil fuels. The Lund researchers, who recently applied for a patent for their discovery, hope to eventually use the new solution to produce hydrogen to power fuel cells that can replace cumbersome batteries in larger vehicles such as planes and boats.

“Linking hydrogen production to a photocatalyst based on abundant metals such as iron means that in the future we could produce hydrogen cheaply and in large quantities completely fossil-free, using sunlight as the only energy source. This will be needed to achieve a fossil-free society,” says Kenneth Wärnmark.

The study, carried out in collaboration with the Ångström Laboratory at Uppsala University, is published in the journal Chemical Communications: “High Turnover Photocatalytic Hydrogen Formation with an Fe(III)N-Heterocyclic Carbene Photosensitise”