In the search for an inexpensive replacement for platinum, researchers have demonstrated an efficient hydrogen-making catalyst that can improve on devices containing such noble metals for hydrogen evolution reaction (HER). In what could be a turning point in the development of large-scale hydrogen fuel applications, the new catalyst contains the common elements of phosphorus and sulfur, and cobalt, a metal that is much cheaper and more abundant than platinum.
It is hoped that hydrogen will one day become a primary fuel, especially as it does not emit carbon dioxide and could be used to store energy as gasoline does now. Although it is normally produced by separating water using electricity, any broad use of hydrogen in this way faces the problem that the platinum or other noble metal that help to split it from water are prohibitively expensive.
"This is a very exciting advance that will have many practical applications in fuel cells, electrocatalytic and solar-driven photoelectrochemical water splitting."Song Jin
The team thinks the device will show the highest catalytic performance among the non-noble metal catalysts so far achieved. As lead researcher Song Jin said, “In the hydrogen evolution reaction, the whole game is coming up with inexpensive alternatives to platinum and the other noble metals.” The catalyst can also be used in conjunction with the energy coming from sunlight, as they demonstrated a proof-of-concept device for using the cobalt catalyst and solar energy to drive hydrogen generation.
Catalysts work to lower the amount of energy required to initiate a chemical reaction, and this new catalyst was found to be nearly as efficient as platinum. The team, whose study was reported in Nature Materials [Cabán-Acevedo et al. Nat. Mater. (2015) DOI: 10.1038/nmat4410], used simulated sunlight in the lab to show their photoelectrolysis cell can split water into hydrogen and oxygen using the catalyst. The tests on solar-driven photoelectrochemical hydrogen generation also demonstrated excellent efficiency. However, there are a range of issues about the catalyst that remain to be resolved, such as the cost of the catalyst compared to the whole system since the best electrolyzers may still need to use platinum.
As the study shows ways to design better catalysts by modifying the electronic structures of the existing catalysts, this could lead to new research into better catalysts of similar compounds or other, different families. The research also has many potential practical applications in fuel cells, electrocatalytic and solar-driven photoelectrochemical water splitting, and the team are now looking to gain a better understanding of the detailed catalytic mechanisms.