- Novel catalysts for hydrogen technology developed
A successful energy transition needs safe and affordable alternatives to fossil fuels.
With the National Hydrogen Strategy 2020, the Federal Government is placing a clear emphasis on hydrogen as a clean and safe energy source. Chemists from the Technical University of Berlin have now published in the renowned journal Nature Communication the molecular mode of action of special nickel oxide catalysts, which are even superior to conventional precious metal catalysts. At the same time, the group published the first PEM fuel cell electrocatalyst in the journal Nature Materials, which is based solely on the unusual catalytic effect of tin.
In order to achieve the goal of greenhouse gas neutrality, Germany must create opportunities to use hydrogen as a decarbonization option. “It makes sense for the Federal Government to use so-called ‘green hydrogen’, i.e. hydrogen that is produced from renewable energies,” says Prof. Dr. Peter Strasser, head of the electrochemistry and electrochemical energy conversion department at the TU Berlin, from whose group the two works originate. Hydrogen is a versatile energy source that paves the way for hydrogen-based mobility in fuel cells, for example, and is used as the basis for synthetic fuels. Green hydrogen is generated by splitting water into hydrogen and oxygen by electrolysis – powered by electricity from renewable energies.
Replace expensive precious metals
“The coupled generation of oxygen is actually the chemical process that causes the most energy losses,” explains Peter Strasser. “So-called Proton Exchange Membrane (PEM) electrolysers use the very expensive and rare noble metal iridium as a catalyst on the anode. Assuming the capacity targets for hydrogen production formulated in the German government’s hydrogen strategy by 2030, we would have to use the entire annual iridium production in the world – to cover a few percent of Germany’s energy needs. ”Together with his team, Peter Strasser explores non-precious metal catalysts Nickel and iron oxides for electrolysers working in alkaline pH conditions. These catalysts accelerate water electrolysis to be superior to iridium. In Nature Communications, the scientists have now published the molecular mode of action of these designer catalysts in great detail. At the same time, a theoretical model of this catalyst was developed in cooperation with colleagues at Purdue University in the USA, which was able to fully reproduce the experimental results that were carried out in cooperation with the Fritz Haber Institute. “This new understanding helps to bring green, efficient and inexpensive hydrogen production within reach,” said Peter Strasser. which was able to fully reproduce the experimental results that were carried out in collaboration with the Fritz Haber Institute.
Tin atoms have a surprising catalytic effect
In the publication in Nature Materials, the scientist and his team describe the discovery of a completely new catalyst for the Proton Exchange Membrane (PEM) fuel cell, in which green hydrogen is converted back into electricity for mobile or stationary applications. “Most electrocatalysts are metals from the sub-groups of the periodic table, such as platinum, iron or silver. Due to their electronic structure, however, metals in the main groups are generally very poor catalysts. However, the new catalyst for the PEM fuel cell is based on the catalytic effect of the main group metal – tin, ”describes Peter Strasser. For this purpose, the researchers embedded individual tin atoms in a layer-like carbon matrix – so-called graphene – and fixed them with nitrogen atoms. The scientists speak of a “single-atom catalyst”. Tested in a fuel cell, it was found that the catalytic effect of the tin-nitrogen-carbon catalyst approximates that of the expensive platinum and even exceeds that of conventional platinum-free catalysts.
In an international cooperation with working groups in the USA, France and Denmark, the atomic structure, as well as the molecular mode of action of the novel tin catalyst, could be examined and clarified in detail.
“If we use tin instead of platinum as a catalyst in the fuel cell, the catalyst costs drop enormously. In addition, tin has other positive chemical properties that can extend the life of the membrane used in the fuel cell, ”adds Peter Strasser.
Nature Communication: https://www.nature.com/articles/s41467-020-16237-1
Nature Materials: https://www.nature.com/articles/s41563-020-0717-5
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