Nov 15 2019
Catalysts are known to speed up chemical reactions, but the extensively used metal platinum is not only rare but also costly.
Scientists from Eindhoven University of Technology (TU/e) collaborated with researchers from China, Japan, and Singapore to develop an alternative catalyst that has 20 times higher activity—a catalyst that has hollow nanocages of nickel-platinum alloy.
Emiel Hensen, a TU/e scientist, prefers to utilize this novel catalyst to create a refrigerator-sized electrolyzer of approximately 10 MW in the future. The study results will be published in the Science journal on November 15th, 2019.
The national government is aiming to get virtually all of the Netherlands’ energy needs from sustainable sources by 2050. Sustainable sources include the wind or the sun. However, these energy sources are not available continuously, and hence it is crucial to preserve the generated energy.
Considering their low energy density, batteries are not appropriate for storing extremely large quantities of energy. Chemical bonds offer a better solution, with hydrogen being the most obvious option of gas. With the help of water, an electrolyzer changes an excess amount of electrical energy into hydrogen, and this gas can then be stored.
At a subsequent stage, a fuel cell does the reverse, that is, it changes the stored hydrogen back into electrical energy. But both types of technologies need a catalyst to speed up the process.
The catalyst that aids in these energy conversions is—owing to its high activity—largely composed of platinum. However, this metal is relatively scarce and very costly. This poses a problem if fuel cells and electrolyzers have to be used on a commercial scale.
Fellow researchers from China therefore developed an alloy of platinum and nickel, which reduces costs and increases activity.
Emiel Hensen, Catalysis Professor, Eindhoven University of Technology
An effective catalyst is one that shows a high activity; it changes more number of water molecules into hydrogen per second.
Hensen continued, “At TU/e, we investigated the influence of nickel on the key reaction steps and to this end we developed a computer model based on images from an electron microscope. With quantum chemical calculations we were able to predict the activity of the new alloy, and we could understand why this new catalyst is so effective.”
Successfully Tested in a Fuel Cell
Apart from the other choice of metal, the scientists also made considerable changes to the morphology. Within the catalyst, the atoms have to bond with the molecules of water and/or oxygen to be able to change them. Therefore, additional binding sites will result in higher activity.
You want to make as much metal surface available as possible. The developed hollow nanocages can be accessed from the outside as well as from the inside. This creates a large surface area, allowing more material to react at the same time.
Emiel Hensen, Catalysis Professor, Eindhoven University of Technology
Using quantum chemical calculations, Hensen has also demonstrated that the activity is further increased by the particular surface structures of the nanocages.
Following calculations in Hensen’s model, it was found that the activity of both solutions combined is 20x, more effective than that of the existing platinum catalysts. The same result was also discovered by the scientists during experimental tests in a fuel cell.
“An important criticism of a lot of fundamental work is that it does its thing in the lab, but when someone puts it in a real device, it often doesn’t work. We have shown that this new catalyst works in a real application,” added Hensen.
A catalyst’s stability should be such that it continuously functions in a house or hydrogen car in the future. Therefore, the investigators tested the catalyst for 50,000 “laps” in the fuel cell, and observed a slight reduction in the activity.
Electrolyzer in Every District
This novel catalyst offers many possibilities—in the form of the fuel cell as well as the reverse reaction in an electrolyzer. Fuel cells, for instance, are utilized in hydrogen-powered cars, while emergency generators with hydrogen-powered fuel cells are already used in certain hospitals.
For example, an electrolyzer can be utilized on wind farms at sea, or maybe even adjacent to every single wind turbine. When compared to transporting electricity, transporting hydrogen is relatively cheaper.
I hope that we will soon be able to install an electrolyzer in every neighborhood. This refrigerator-sized device stores all the energy from the solar panels on the roofs in the neighborhood during the daytime as hydrogen.
Emiel Hensen, Catalysis Professor, Eindhoven University of Technology
Hensen continued, “The underground gas pipelines will transport hydrogen in future, and the domestic central heating boiler will be replaced by a fuel cell, the latter converting the stored hydrogen back into electricity. That's how we can make the most of the sun.”
However, for this to happen, the electrolyzer still has to go through a great deal of development. Along with industrial partners from the Brabant region and other TU/e scientists, Hensen is currently involved in the start-up of the energy institute of TU Eindhoven. The institute is aiming to advance the existing commercially available electrolyzers to a refrigerator-size electrolyzer of approximately 10 MW.
Source: https://www.tue.nl/en/