Multifunctional elecrocatalysts for clean energy conversion

One of the main challenges of todays society is the impending energy crisis. Green hydrogen is gaining importance worldwide as a sustainable energy carrier and feedstock for the chemical industry. Hydrogen, produced by electrolysis using renewable electricity, is essential for a successful energy transition and for meeting international climate targets. Another approach is to convert CO2 and water into sustainable fuels. Efficient generation of fossil-free hydrogen at low cost requires the development of new electrocatalysts, which are materials that use electric energy from renewable sources (e.g. from sunlight) to accelerate these reactions and enhance their efficiency in a sustainable way. The interdisciplinary project MultiCat (Multifunctional electrocatalysts for clean energy conversion), which combines four groups from Austria, Poland, and Slovenia, is dedicated to the development of next-generation electrocatalysts for efficient generation of hydrogen and other solar fuels from water and CO 2. We will synthesize transition metal phosphides (TMPs) and carbides (TMC) to replace the currently used, but expensive noble metal electrocatalysts. In addition, we will also introduce a new type of material, called metal-organic frameworks (MOFs). These exciting materials consist of very small molecular metal-oxide cluster that are connected by organic molecules to make porous structures with currently the highest known surface areas. We expect that small reactant molecules, such as CO 2, can enter these small pores and react with the many metal-oxide clusters to induce the desired electrocatalytic reaction. It will be crucial to enhance the stability of these materials in water and to optimize their electronic conductivity by tuning the organic ligand interactions with the metal -oxide centers. Beside synthesizing these materials, the project aims to unravel the underlying reaction mechanisms and identify the individual processes that limit their speed and efficiency, in order to improve their performance as electrocatalyst. For this, we will use a broad range of theoretical and experimental techniques to study the chemical, catalytic and electronic nature of the materials during (in-situ) and after (ex-situ) the electrocatalytic reactions. The project uniquely combines complementary research skills of the four partners that will help advancing the fields of hydrogen technology and environmentally-friendly low- temperature electrochemical energy conversion.

In our research, we work with special materials called metal-organic frameworks (MOFs). You can imagine them like tiny sponges made from metal atoms connected by organic building blocks. They are full of extremely small holes, called pores, which make them very useful. These pores can trap harmful chemicals from water, such as pesticides, and they can also help important chemical reactions happen faster. This is especially useful for producing clean energy. One major use of MOFs in our work is electrocatalysis. Electrocatalysis means using electricity and a special material, called a catalyst, to make chemical reactions happen more easily and with less energy. We use MOFs to help split water into hydrogen and oxygen, which is an important step for producing clean hydrogen fuel. There are two key reactions in this process. HER (Hydrogen Evolution Reaction) is the reaction where hydrogen gas is produced from water. Hydrogen is considered a clean fuel because it can provide energy without causing pollution. OER (Oxygen Evolution Reaction) is the reaction where oxygen gas is produced from water. It happens at the same time as HER and is necessary for the full water-splitting process. The challenge is that although MOFs have many pores, most of them are very small and hidden deep inside the material. Larger molecules cannot easily reach these important active areas, so much of the material is not used efficiently. To solve this, we redesign MOFs in smarter ways. First, we carefully remove some of the "linkers," which are like bridges holding the structure together. We do this in a controlled way without destroying the material. This creates larger channels inside the MOF. Instead of only tiny pores, the material now has both small and larger pores. This is called a hierarchical structure, and it helps molecules move more easily through the material. Second, we choose different types of linkers when building the MOF. This allows us to control the size, shape, and connection of the pores. In this way, we can design the material for specific jobs, such as cleaning polluted water or improving HER and OER reactions. Another exciting part of our work is that MOFs are not fixed-they can improve while being used. During reactions, especially in electrocatalysis, their surface can change and create new, stronger active sites. Because of this, our MOFs work much better. They remove harmful chemicals like glyphosate from water faster and more efficiently, while also improving clean energy production. Our work is important in three ways: for science, by showing that materials can be smart and adaptable; for the environment, by helping clean water and cleaner energy production; and for people, by supporting safer drinking water and a more sustainable future.