Green hydrogen: Nanostructured nickel silicide shines as a catalyst

Electrical energy from wind or sun can be stored as chemical energy in hydrogen, an excellent fuel and energy carrier. The prerequisite for this, however, is efficient electrolysis of water with inexpensive catalysts. For the oxygen evolution reaction at the anode, nanostructured nickel silicide now promises a significant increase in efficiency. This was demonstrated by a group from the HZB, Technical University of Berlin and the Freie Universität Berlin as part of the CatLab research platform with measurements among others at BESSY II.

Electrolysis might be a familiar concept from chemistry lessons in school: Two electrodes are immersed in water and put under voltage. This voltage causes water molecules to break down into their components, and gas bubbles rise at the electrodes: Oxygen gas forms at the anode, while hydrogen bubbles form at the cathode. Electrolysis could produce hydrogen in a CO2-neutral way – as long as the required electricity is generated by fossil free energy forms such as sun or wind.

The only problem is that these reactions are not very efficient and extremely slow. To speed up the reactions, catalysts are used, based on precious and rare metals such as platinum, ruthenium or iridium. For large-scale use, however, such catalysts must consist of widely available and very cheap elements.

Read more on the HZB website

Image: Crystalline nickel silicide (left) is chemically transformed into nanostructured material with excellent catalytic properties for the electrolytic splitting of water and the production of valuable nitrile compounds. 

Credit: © P. Menezes /HZB/TU Berlin

Green hydrogen: Why do certain catalysts improve in operation?

Crystalline cobalt arsenide is a catalyst that generates oxygen during electrolytic water splitting in the production of hydrogen. The material is considered to be a model system for an important group of catalysts whose performance increases under certain conditions in the course of electrolysis. Now a HZB-team headed by Marcel Risch has observed at BESSY II how two simultaneous mechanisms are responsible for this. The catalytic activity of the individual catalysis centres decreases in the course of electrolysis, but at the same time the morphology of the catalyst layer also changes. Under favourable conditions, considerably more catalysis centres come into contact with the electrolyte as a result, so that the overall performance of the catalyst increases.

As a rule, most catalyst materials deteriorate during repeated catalytic cycles – they age. But there are also compounds that increase their performance over the course of catalysis. One example is the mineral erythrite, a mineral compound comprising cobalt and arsenic oxides with a molecular formula of (Co3(AsO4)2∙8H2O). The mineral stands out because of its purple colour. Erythrite lends itself to accelerating oxygen generation at the anode during electrolytic splitting of water into hydrogen and oxygen.

Read more in the HZB website

Image: Schematic of the electrochemical restructuring of erythrite. The fine needle-like structure melts during the conversion from a crystalline material to an amorphous one, which is porous like a Swiss cheese.

Credit: © HZB

Turning straw into gold?

A more profitable and eco-friendly method for turning biomass into biochemicals and green hydrogen

Many have dreamed of being able to turn straw into gold like the fabled Rumpelstiltskin. While this may not be possible in the literal sense, scientists are using sunlight to turn straw into something more valuable.

With the aid of technology from the Canadian Light Source (CLS) at the University of Saskatchewan, Canadian researchers have made important advances to use the power of the sun to convert biomass like wheat straw into hydrogen fuel and value-added biochemicals. This method is more efficient, eco-friendly and lucrative.

Producing energy from biomass, or plant material, has been studied for more than four decades, said Dr. Jinguang Hu, assistant professor at the University of Calgary (UCalgary). The two most common processes are thermo-chemical and biological, but these are still carbon intensive and are not economically feasible.

Read more on the CLS website

Image: The UCalgary team is observing a photo-reactor that is being used for a photoreforming reaction with wheat straw. Left to right: Prof. Md Golam Kibria, Dr. Adnan Khan (Research Associate), Dr. Heng Zhao (Post doctoral fellow), Prof. Jinguang Hu.

Credit: Prof. Hu and Kibria group.