Clean hydrogen energy is a good alternative to fossil fuels and is critical for achieving carbon neutrality. Researchers around the world are looking for ways to enhance the efficiency and lower the cost of hydrogen production, particularly by improving the catalysts involved. Recently, a research team from City University of Hong Kong (CityU) developed a new, ultra-stable hydrogen evolution reaction (HER) electrocatalyst, which is based on two-dimensional mineral gel nanosheets and does not contain any precious metals. The catalyst can be produced in large scale and can help achieve a lower hydrogen price in the future.
Electrochemical hydrogen evolution reaction (HER) is a widely used hydrogen-generation method. But commercial HER electrocatalysts are made from precious metals, which are expensive. On the other hand, single-atom catalysts have promising potential in catalytic HER applications because of their high activity, maximised atomic efficiency, and minimised catalyst usage. But the conventional fabrication process of single-atom catalysts is complicated. It generally involves introducing the targeted single-atom metal to the substrate precursor followed by thermal treatment, usually higher than 700 ℃, which requires a lot of energy and time.
In this regard, a research team co-led by CityU materials scientists have developed an innovative, cost-effective and energy-efficient way to produce a highly efficient HER single-atom electrocatalyst that uses precious-metal-free mineral hydrogel nanosheets as a precursor.
"Compared with other common single-atom substrate precursors, such as porous frameworks and carbon, we found that mineral hydrogels have great advantages for mass production of electrocatalysts due to the easy availability of the raw materials, simple and environmental-friendly synthetic procedure, and mild reaction conditions," said Professor Lu Jian, Chair Professor in the Department of Mechanical Engineering (MNE) and the Department of Materials Science and Engineering (MSE) at CityU, who led the research.
Their electrocatalyst precursor is prepared using a simple method. First, solutions of polyoxometalate acid (PMo) and ferric ions (Fe3+) are mixed at room temperature, resulting in novel two-dimensional iron–phosphomolybdic-acid nanosheets. After excess water is removed by centrifugation, the nanosheets become mineral hydrogel free of any organic molecules. The process is much more convenient and economical than the previously reported processes that typically require high temperature and pressure, and longer time for the self-assembly of single-atom substrate precursors.
