Prof. Xiaodong Wang and Tao Zhang’s team from DICP has made continuous effort on the research and development of nano and subnano catalysts. Recently, they for the first time found that the total oxidation of CO can occur at cryogenic temperature of -50 ^oC over platinum group metals (PGMs, including Pt, Ir, Ru, Rh, Pd) with a novel TiO₂ supported Rh subnano catalyst, which was rated as a landmark work by the reviewers. This work was published as VIP paper (top 5%) in Angew. Chem. Int. Ed. and selected as back cover story in the latest issue (http://onlinelibrary.wiley.com/doi/10.1002/anie.201600636/full).

The high dispersions of supported noble metals are not only beneficial for the efficient atomic utilization but also for the optimization of adsorption and reaction behaviors of reactants during catalytic reactions. The catalytic CO oxidation over supported metal catalysts have great practical values in the purification of industrial hydrogen, automotive exhaust control, as well as the elimination of environmental pollutions, which have also been extensively studied as a probe reaction for the understanding of relationships between catalytic performance and structural properties. CO oxidation on PGMs has been studied for almost a century; it has been widely accepted that the strongly adsorbed CO on PGMs significantly inhibits the activation of O₂, thus resulting in high work temperature (usually > 100 ^oC).

Previous studies by this team have suggested that CO oxidation activity can be significantly enhanced when the PGMs are downsized in a subnano scale. (Angew. Chem. Int. Ed. 2012, 51, 2920; J. Catal. 2014, 319, 142; ChemCatChem 2014, 6, 547; Appl. Catal. B 2016, 184, 299), but it still remains great challenge for their utilization at ambient temperatures, not to mention cryogenic temperature. On this basis, they recently prepared a novel TiO₂ supported subnano Rh catalyst with sizes of 0.4~0.8 nm as the first PGMs catalysts for CO oxidation at cryogenic temperature, which can realize the oxidation of CO at -100 ^oC with activity even comparable with the standard Au/TiO₂ catalyst. With detailed characterizations and DFT calculations, it was identified that at cryogenic temperatures O₂ was activated at the perimeters between subnano Rh and TiO₂ support as Rh-O-O-Ti (superoxide), and reacted with the weakly adsorbed CO species on TiO₂. This work would not only make people re-recognize the CO oxidation on PGM catalysts, but also provide new insights for the design of novel active catalysts.

This work was supported by the National Natural Science Foundation of China.