Catalytically Active Rh Sub‐Nanoclusters on TiO₂ for CO Oxidation at Cryogenic Temperatures

The discovery that gold catalysts could be active for CO oxidation at cryogenic temperatures has ignited much excitement in nanocatalysis. Whether the alternative Pt group metal (PGM) catalysts can exhibit such high performance is an interesting research issue. So far, no PGM catalyst shows activity for CO oxidation at cryogenic temperatures. In this work, we report a sub‐nano Rh/TiO 2 catalyst that can completely convert CO at 223 K. This catalyst exhibits at least three orders of magnitude higher turnover frequency (TOF) than the best Rh‐based catalysts and comparable to the well‐known Au/TiO 2 for CO oxidation. The specific size range of 0.4–0.8 nm Rh clusters is critical to the facile activation of O 2 over the Rh–TiO 2 interface in a form of Rh−O−O−Ti (superoxide). This superoxide is ready to react with the CO adsorbed on TiO 2 sites at cryogenic temperatures.