Clean hydrogen energy is a good alternative to fossil fuels and is critical to achieving carbon neutrality. Researchers around the world are looking for ways to increase the efficiency and reduce the cost of hydrogen production, especially by improving the relevant catalysts. Recently, a research team from City University of Hong Kong (CityU) developed a new, ultra-stable hydrogen evolution reaction (HER) electrocatalyst based on two-dimensional mineral gel nanolayers and free of any precious metals. The catalyst could be produced on a large scale and could help achieve a lower hydrogen price in the future.
The electrochemical hydrogen evolution reaction (HER) is a widely used hydrogen production method. However, commercial HER electrocatalysts are made from precious metals, which are expensive. On the other hand, monoatomic catalysts have promising potential in catalytic HER applications due to their high activity, maximum atomic efficiency and minimal catalyst usage. However, the conventional manufacturing process of monoatomic catalysts is complex. It usually involves introducing the targeted monoatomic metal to the substrate precursor followed by heat treatment, usually higher than 700℃, which requires a lot of energy and time.
In this context, a research team led by CityU materials scientists has developed an innovative, cost-effective and energy-efficient way to fabricate a highly efficient HER single-atom electrocatalyst that uses precious metal-free mineral hydrogel nanolayers as a precursor. .
“Compared to other common monoatomic substrate precursors such as porous frameworks and carbon, we found that mineral hydrogels have major advantages for mass production of electrocatalysts due to the easy availability of raw materials, simple and environmentally friendly synthetic procedure. CityU Department of Mechanical Engineering (MNE) and Materials Science conducted the research. Light reaction conditions,” said Professor Lu Jian, Head of the Department of Energy and Engineering (MSE).
Electrocatalyst precursors are prepared using a simple method. First, polyoxometalate acid (PMo) and ferric ions (Fe3+) at room temperature, new two-dimensional iron-phosphomolybdic acid nanolayers are obtained. After removing excess water by centrifugation, the nanolayers become mineral hydrogel without any organic molecules. The process is much more convenient and economical than previously reported processes, which typically require high temperature and pressure and longer time for self-assembly of monoatomic substrate precursors.
After another phosphating (at 500°C) of this mineral gel precursor, a dispersed heterogeneous nanolayer catalyst with single iron atoms (“Fe/SAs@Mo-based-HNSs”) is formed, avoiding the time-consuming production process. loading of single atoms onto the substrate.
Experiments found that the new catalyst exhibited excellent electrocatalytic activity and long-term durability at HER, revealing an overpotential of only 38.5 mV at 10 mA cm-1.-2and ultra stability with no performance degradation over 600 hours at current density up to 200 mA cm²-2.
“This is one of the best performances achieved by non-noble metal HER electrocatalysts,” said Professor Lu. “The unique idea of using mineral gel to synthesize monoatomic dispersed heterogeneous catalysts provides an important theoretical foundation and direction for the next step in the scalable production of inexpensive and efficient catalysts that can contribute to reducing the cost of hydrogen production in the long run.”
Their findings were published in the scientific journal Nature Communication Under the heading “Two-dimensional mineral hydrogel-derived monoatomic linked heterostructures for ultrastable hydrogen evolution”.
The first author of the article is Dr Lyu Fucong from CityU. Associated authors are Professor Lu, Associate Professor at MSE, Dr. Dr. Li Yangyang and Assistant Professor at the Harbin Institute of Technology’s School of Science.
Research, Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project, China National Key R&D Program, China National Natural Science Foundation, Guangdong Fundamental and Applied Fundamental Research Foundation, Science, Technology and Innovation Commission of Shenzhen Municipality, and CityU Hong Kong Innovation and Technology Commission through the Hong Kong Branch of the National Precious Metals Materials Engineering Research Centre.
To overcome the high cost problem of commercial platinum-based electrocatalysts, the team led by Professor Lu recently made another breakthrough. They provided a solution through rational nanostructured alloy design to develop a low-cost, high-performance electrocatalyst.
Professor Lu’s team is conducting in-depth research on alloy nanostructures that have both crystalline and amorphous phases simultaneously. They discovered that local chemical inhomogeneity, short-range order, and severe lattice distortion in the nanocrystalline phase are desirable for application in catalysis, while the amorphous phase can offer abundant active sites with a lower energy barrier for the hydrogen evolution reaction. Therefore, they devoted their research efforts to designing and building biphasic alloys to be excellent electrocatalysts for hydrogen production.
They proposed a new alloy and nanostructure design strategy based on thermodynamics. First, they estimated the compositional range of “crystal-amorphous” binary phase formation based on amorphous forming ability (GFA). Then, using the easy magnetron co-sputtering method, they successfully prepared the aluminum-based alloy catalyst with a “crystal-amorphous” dual-phase nanostructure.
Thanks to this nanostructure, the new catalyst showed better electrocatalytic performance than the commercial platinum-based electrocatalyst in alkaline solution, with an overpotential of only 28.8 mV at 10 mA cm-1.-2.
“In this new aluminum-based alloy catalyst, we use ruthenium as the noble metal component, which is less expensive than platinum. Therefore, it may be less costly than commercial platinum-based electrocatalysts,” said Professor Lu. “And apart from hydrogen evolution, the nano-dual-phase electrocatalysis mechanism can be applied to other catalytic systems. The ‘crystal-glass’ nanostructure design offers a new approach for developing next-generation catalysts.”
Findings published Science Advances, under the heading “An Al-based electrocatalyst with a crystal glass nanostructure for the hydrogen evolution reaction”. Former postdoctoral researcher Dr Liu Sida (currently Professor at Shandong University) and MSE PhD student Mr. Li Hongkun are co-first authors. The corresponding authors are Professor Lu and Dr Li from CityU and Professor Wu Ge from Xi’an Jiaotong University. Other researchers from CityU include Dr Zhou Binbin, a former postdoc at MEB (currently Research Associate Professor at Shenzhen National Institute for Advanced Electronic Materials Innovation), Mr. Zhong Jing and Ms. Li Lanxi, both MSE PhD students, and MNE’s There is Mr. Yan Yang. PhD student.