In cooperation with Profs.Jingyue Liu (DICP) and Jun Li (Tsinghua University), Prof. Tao Zhang of DICP has recently made a progress on a new single-atom catalyst (SAC). This novel catalyst is composed of iridium (Ir) atoms supported on FeOx and possess an extremely low Ir loading amount (0.01 wt%). They found that the specific activity of the Ir1/FeOx SAC was one order of magnitude higher in a water-gas shift reaction (WGSR) than both its cluster or nanoparticle counterparts. Extensive studies reveal that the single atoms accounted for ~70% of the total activity in those catalysts which contain single-atom, subnano clusters, and nanoparticles, thus serving as the most important site of catalysis. These results were published in a communication to the J. Am. Chem. Soc. (http://pubs.acs.org/doi/abs/10.1021/ja408574m).
Single-atom catalysis is a relatively new concept in the field of heterogeneous catalysis and has the ability to bridge the gap between homogeneous and heterogeneous catalysis. In 2011, a collaborative team led by Profs. Zhang, Liu, and Li reported the first practical application of a Pt1/FeOx SAC. These data led to the concept of “single-atom catalysis” (Nat. Chem. 2011, 3, 634). Since that time, many scientists have further developed this concept. In 2013, Prof. Zhang’s group was invited to write a review on “single-atom catalysis” (Acc. Chem. Res. 2013, 46, 1740).
Supported Ir catalysts are commonly used in the decomposition of propellants, such as hydrazine and N2O, though they have been rarely investigated in WGSR. The group of Prof. Zhang found that FeOx will stabilize not only the Pt single-atom, but also Ir subnano clusters (Angew. Chem. Int. Ed. 2012, 51, 2920). Based on these results, they successfully synthesized a new Ir1/FeOx SAC and applied it in WGSR at temperature of 300 oC. Studies have revealed that the single atoms serve as key active sites, and exhibit good stability at elevated temperatures. These efforts, led by DICP, not only increase our understanding of heterogeneous catalysis on an atomic level, but also have broad implications for designing supported metal catalysts; catalysts with better performance and lower cost for a variety of industrial chemical reactions. (by Jian Lin)