How did the Polish scientists manage to combine the three resources of the future: water, hydrogen and carbon? Let us take you to the Graphene Laboratory at the Faculty of Chemical and Process Engineering at the Warsaw University of Technology.
How is the catalyst that you are working on going to change the method of hydrogen production?
Marta Mazurkiewicz-Pawlicka, MSc: In our laboratory, we deal with carbon nanomaterials in a broad sense and their combinations with other materials. For instance, we are developing a technology producing a cheaper material that can be mass-produced more easily and that is used to cover electrodes used in the water electrolysis process. Molybdenum disulfide (MoS2) is a catalyst in this process, that is a material which accelerates the reaction leading to the production of hydrogen. Its application in hydrogen production is well-known. We want to adopt it to large-scale industrial production, which is why this solution must be cost-effective.
Zuzanna Bojarska, MSc: Molybdenum disulfide replaces considerably more expensive platinum, which has been used so far.[1] Additionally, we combine it with carbon nanomaterials, which boosts the activity of the material obtained. This way, the entire production process is more viable.
What makes this technology innovative?
M.M-P: We continue our research on the application of collision reactors for synthesizing molybdenum disulfide, which was initiated by Professor Łukasz Makowski from the Product Engineering Team operating at the Faculty of Chemical and Process Engineering at the Warsaw University of Technology. The innovative part of our project is about using collision reactors to generate molybdenum disulfide and adding carbon nanomaterials during the synthesis. As a base for embedding molybdenum disulfide, we use for instance reduced graphene oxide or carbon nanotubes.
B.: There are many methods of obtaining molybdenum disulfide, which are usually very expensive and use microwaves or high temperature and high pressure. However, not much material can be generated this way. By using a collision reactor, we can produce larger quantities of the catalyst in a continuous, repetitive and scalable manner.
What is a collision reactor and what leads to the reactions occurring therein?
B.: A reactor has a very simple structure, similar to a letter “T”[2]. On both sides, there are inlets of substrates which collide on a very small space. This leads to intensive mixing, thanks to which particles are created in a continuous and repetitive manner. Then, we clean the suspension, most frequently by applying centrifugal forces and soaking. A possibility of modifying the reactor and using various carbon nanomaterials, e.g. replacing graphene with cheaper carbon nanotubes, offers large opportunities for the industry. Thanks to this, we can produce catalysts in a continuous manner, but most importantly, in a cheaper manner.
Why are carbon nanoparticles used in this technology?
M.M-P: Molybdenum disulfide is characterized by low conductivity. We amplify this property by using carbon nanomaterials. Additionally, they are carriers of the catalyst so that smaller disulfide particles are generated in the reactor, which are more catalytically active.
Thanks to their structure, carbon nanomaterials make it easier for disulfide to deposit. Thanks to this, more small particles are created on the surface of carbon. We obtain a material that is more active, its conductivity increases as well. Therefore, it can be used in water electrocatalysis.
What electrolyzers can molybdenum be used in?
Materials we have developed may be used in electrolyzers with a polymer-electrolyte membrane (PEM). Additionally, thanks to the modification of catalysts with nanoparticles with photocatalytic properties, the solution can be applied in photoelectrocatalytic electrolyzers.
This means that you two have developed a material that an electrolyzer manufacturer must use to create (mold, cut out) elements/electrodes?
We have confirmed the activity of the material developed on a laboratory scale by means of electrochemical measurements. We really would like to test our material in an operational device and we are ready to help to develop a method of using our catalyst to produce electrodes in an electrolyzer.
Companies from which industries could establish cooperation in order to develop a technology using catalysts?
M.M-P: It will be possible to intensify hydrogen production by using a collision reactor to produce molybdenum disulfide. In order for this to happen, we need scientists and investors to join forces. We also need a demonstrator on which we could be testing subsequent solutions. This requires changing entrepreneurs’ attitude. As scientists, we are the first of many links. We still do not have solutions ready to be implemented on an industrial scale. We need cooperation, we need to build a demonstrator, conduct research in cooperation with a company producing electrolyzers.
B.: All over the world, there are discussions on how to produce hydrogen quickly and cheaply. We are also working on such technologies, but we need more financial support in order to proceed to the implementation phase. We also need various environments to cooperate: scientists and investors so that the solutions that we have developed can be implemented in the industry on a large and profitable scale.
Why is it so important to produce green hydrogen?
M.M-P: Currently, hydrogen is produced mainly with the use of fossil fuels. It is unfavorable since we emit greenhouse gases, generate pollution and have limited resources of raw materials. This way, we contribute to climate change, which is why a cleaner and more effective method of hydrogen production is being searched for. We respond to these needs when we obtain hydrogen from water.
How do your projects combine the two remaining resources from 3W, that is water and carbon?
B.: In many projects, we test graphene or carbon nanomaterials. Currently, we are working on extending the application of our hybrid structures. In one of the projects, we are examining the possibility of obtaining hydrogen with the use of solar radiation.
M.M-P: We add particles of photocatalysts, e.g. titanium dioxide, to the hybrid of molybdenum disulfide and nanocarbon. This way, we want to use solar energy to intensify water electrolysis. Photoelectrolysis is a solution to the problem of low efficiency of photocatalysis and high costs of electrolysis, which is why we want to create a material evincing high photoelectrocatalytic activity.
B.: Apart from the catalysts themselves, we are also working on another application of the hybrid of molybdenum disulfide and carbon nanomaterials by using it as a lubricant, that is simply a grease additive. Studies on an engine have indicated that it reduces friction in the engine, its consumption and emissions of exhaust fumes.
M.M-P: For several years, we have also been working on matters that are related to fuel cells, not only those powered by hydrogen, but also those powered by other liquid fuels, e.g. formic acid. These solutions are also dominated by carbon nanomaterials. They are usually used as carriers for catalysts used as a cathode (where an oxidant is reduced) and an anode (where fuel is oxidized). A cell that is powered by formic acid has several advantages, including easy storage of fuel. Unfortunately, when it is working, water is not the only substance that is emitted, carbon dioxide is emitted as well, but in significantly smaller quantities that in the case of e.g. combustion engines. Our research is focused on generating catalysts that are characterized by high activity, low price and longevity. We would not have reached our objectives if it had not been for carbon nanomaterials.
[1] Currently, a kilogram of platinum costs approx. $ 30,000. Molybdenum, which is naturally present as ore, can be purchased at the price of $10–150 per kilogram, depending on its form.
[2] We encourage you to watch the video explaining how the reactor works: https://www.youtube.com/watch?v=mKcy5n5mTUE
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