1. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China


2. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China


3. Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji 192-0397, Tokyo, Japan


4. Japan Science and Technology Agency, CREST, 4-1-8 Hon-Cho, Kawaguchi 332-0012, Saitama, Japan


5. These authors contributed equally to this work.

Correspondence to: Wenjie Shen¹ Correspondence and requests for materials should be addressed to W.S. (Email: shen98@dicp.ac.cn).

Low-temperature oxidation of CO, perhaps the most extensively studied reaction in the history of heterogeneous catalysis, is becoming increasingly important in the context of cleaning air and lowering automotive emissions^{1, 2}. Hopcalite catalysts (mixtures of manganese and copper oxides) were originally developed for purifying air in submarines, but they are not especially active at ambient temperatures and are also deactivated by the presence of moisture^{3, 4}. Noble metal catalysts, on the other hand, are water tolerant but usually require temperatures above 100 °C for efficient operation^{5, 6}. Gold exhibits high activity at low temperatures and superior stability under moisture, but only when deposited in nanoparticulate form on base transition-metal oxides^{7, 8, 9}. The development of active and stable catalysts without noble metals for low-temperature CO oxidation under an ambient atmosphere remains a significant challenge. Here we report that tricobalt tetraoxide nanorods not only catalyse CO oxidation at temperatures as low as –77 °C but also remain stable in a moist stream of normal feed gas. High-resolution transmission electron microscopy demonstrates that the Co₃O₄ nanorods predominantly expose their {110} planes, favouring the presence of active Co³⁺ species at the surface. Kinetic analyses reveal that the turnover frequency associated with individual Co³⁺ sites on the nanorods is similar to that of the conventional nanoparticles of this material, indicating that the significantly higher reaction rate that we have obtained with a nanorod morphology is probably due to the surface richness of active Co³⁺ sites. These results show the importance of morphology control in the preparation of base transition-metal oxides as highly efficient oxidation catalysts.