Copper−ceria as one of the very active catalysts for oxidation reactions has been widely investigated in heterogeneous catalysis. In this work, copper oxide (1 wt % Cu loading) deposited on both ceria nanospheres with a {111}/{100}-terminated surface (1CuCe-NS) and with nanorod exposed {110}/{100} faces (1CuCe-NR) have been prepared for the investigation of crystal plane effects on CO oxidation. Various structural characterizations, especially including aberration-corrected scanning transmission electron microscopy (Cs-STEM), X-ray absorption fine structure (XAFS) technique, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), were used to precisely determine the structure and status of the catalysts. It is found that the copper oxides were formed as subnanometer clusters and were uniformly dispersed on the surface of the ceria support. The results from XAFS combined with the temperatureprogrammed reduction technique (H 2 -TPR) reveal that more reducible CuO x clusters with only Cu−O coordination structure exclusively dominated in the surface of 1CuCe-NS, while the Cu species in 1CuCe-NR existed in both CuO x clusters and strongly interacting Cu-[O x ]-Ce. In situ DRIFTS results demonstrate that the CeO 2 -{110} face induced a strongly bound Cu-[O x ]-Ce structure in 1CuCe-NR which was adverse to the formation of reduced Cu(I) active sites, resulting in low reactivity in CO oxidation (r CO = 1.8 × 10 −6 mol CO g cat −1 s −1 at 118 °C); in contrast, CuO x clusters on the CeO 2 -{111} face were easily reduced to Cu(I) species when they were subjected to interaction with CO, which greatly enhanced the catalytic reactivity (r CO = 5.7 × 10 −6 mol CO g cat −1 s −1 at 104 °C). Thus, for copper−ceria catalyst, in comparison with the well-known reactive {110} CeO2 plane, {111} CeO2 , the most inert plane, exhibits great superiority to induce more catalytically active sites of CuO x clusters. The difference in strength of the interaction between copper oxides and different exposed faces of ceria is intrinsically relevant to the different redox and catalytic properties.

The construction of stable active site in nanocatalysts is of great importance but is a challenge in heterogeneous catalysis. Unexpectedly, coordination-unsaturated and atomically dispersed copper species were constructed and stabilized in a sintered copper–ceria catalyst through air-calcination at 800 °C. This sintered copper–ceria catalyst showed a very high activity for CO oxidation with a CO consumption rate of 6100 μmolCO·gCu –1·s–1 at 120 °C, which was at least 20 times that of other reported copper catalysts. Additionally, the excellent long-term stability was unbroken under the harsh cycled reaction conditions. Based on a comprehensive structural characterization and mechanistic study, the copper atoms with unsaturated coordination in the form of Cu1O3 were identified to be the sole active site, at which both CO and O2 molecules were activated, thus inducing remarkable CO oxidation activity with a very low copper loading (1 wt %).

For high-temperature catalytic reaction, it is of significant importance and challenge to construct stable active sites in catalysts. Herein, we report the construction of sufficient and stable copper clusters in the copper‒ceria catalyst with high Cu loading (15 wt.%) for the high-temperature reverse water gas shift (RWGS) reaction. Under very harsh working conditions, the ceria nanorods suffered a partial sintering, on which the 2D and 3D copper clusters were formed. This partially sintered catalyst exhibits unmatched activity and excellent durability at high temperature. The interaction between the copper and ceria ensures the copper clusters stably anchored on the surface of ceria. Abundant in situ generated and consumed surface oxygen vacancies form synergistic effect with adjacent copper clusters to promote the reaction process. This work investigates the structure-function relation of the catalyst with sintered and inhomogeneous structure and explores the potential application of the sintered catalyst in C1 chemistry.

Copper manganese composite (hopcalite) catalyst has been widely explored for low-temperature CO oxidation reactions. However, the previous reports on the stabilization of such composite catalysts have shown that they deactivated severely under moist conditions. Herein, we developed an α-MnO 2 nanorod-supported copper oxide catalyst that is very active and stable for the conditions with or without moisture by the deposition precipitation (DP) method. Incredibly, the CuO/MnO 2 DP catalyst (with 5 wt % copper loading) achieves superior activity with a reaction rate of 9.472•s −1 even at ambient temperatures, which is at least double times of that for the reported copper-based catalyst. Additionally, the CuO/MnO 2 DP catalyst is significantly more stable than the copper manganese composite catalysts reported in the literature under the presence of 3% water vapor as well as without moisture. A correlation between the catalytic CO oxidation activity and textural characteristics was derived via multitechnique analyses. The results imply that the superior activity of the CuO/MnO 2 DP catalyst is associated with the proper adsorption of CO on partially reduced copper oxide as Cu(I)−CO and more surface oxygen species at the interfacial site of the catalyst.

In situ morphological transition and turn-on fluorescence of self-assembled NDI derivatives driven by hydrazine hydrate are realized through H-bonding and charging of aromatic building blocks, demonstrating a stimuli-responsive supramolecular system useful for visual detection of hydrazine hydrate.