Researchers have progressively broadened the conventional main group elements atom types in A-sites to encompass subgroup elements having an outer layer three-dimensional (3D) electronic structure. There has not been much study done on MAX phases with A-site elements that have 4d/5d orbital electronic structures, though.
After researching this little-known area, Professor Qing Huang and associates suggested a generic A-site alloying approach. Because the chemical composition and crystal structure of MAX phases vary widely, this technique allows the synthesis of over 100 MAX phases with noble metal-occupied elements at the A-site of the crystals.
In particular, the A atomic layers contain one or more of the six noble metals (ruthenium, rhodium, palladium, iridium, platinum, and gold), with other solid solution A-site elements such as gallium, indium, germanium, tin, and others being chosen at random. The M-site elements are niobium, vanadium, and titanium.
Noble metal-occupied MAX phases with various geometries were created by selecting the source carbon powders. For the alkaline hydrogen evolution reaction, the Pt-occupied MAX phase generated in this work showed greater catalytic performance compared to commercial Pt/C, including lower overpotential, lower Tafel slope, higher mass activity, and better cyclic stability.
The noble metal-occupied MAX phases that result from general A-site alloying have a wide range of potential uses, including electrocatalysis.
This project was funded by the "Pioneer" and "Leading Goose" R&D Program of Zhejiang, the Zhejiang Province Special Support Program for High-level Talents, and the National Natural Science Foundation of China etc.
Journal Reference:
Li, Y., et al. (2024) A-site alloying-guided universal design of noble metal-based MAX phases. Matter. doi.org/10.1016/j.matt.2023.12.006.