The crucial role of the metal–oxide interface in the catalysts of the water–gas shift (WGS) reaction has been recognized, while the precise illustration of the intrinsic reaction at the interfacial site has scarcely been presented. Here, two kinds of gold–ceria catalysts with totally distinct gold species, <2 nm clusters and 3 to 4 nm particles, were synthesized as catalysts for the WGS reaction. We found that the gold cluster catalyst exhibited a superiority in reactivity compared to gold nanoparticles. With the aid of comprehensive in situ characterization techniques, the bridged −OH groups that formed on the surface oxygen vacancies of the ceria support are directly determined to be the sole active configuration among various surface hydroxyls in the gold–ceria catalysts. The isotopic tracing results further proved that the reaction between bridged surface −OH groups and CO molecules adsorbed on interfacial Au atoms contributes dominantly to the WGS reactivity. Thus, the abundant interfacial sites in gold clusters on the ceria surface induced superior reactivity compared to that of supported gold nanoparticles in catalyzing the WGS reaction. On the basis of direct and solid experimental evidence, we have obtained a very clear image of the surface reaction for the WGS reaction catalyzed by the gold–ceria catalyst.

Well-defined and strikingly monomorphic Pt–Pd alloy nanoflowers (Pt–Pd ANFs) with dominant {111} facets were successfully synthesized through a facile cochemical reduction method in a poly(allylamine hydrochloride) (PAH) based aqueous solution. The detailed morphology, composition, and structure of the Pt–Pd ANFs were investigated by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), nitrogen adsorption–desorption isotherms (SADI), EDS mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), demonstrating the Pt–Pd ANFs were highly porous and a self-supported structure. The formation mechanism of the Pt–Pd ANFs were investigated by TEM and Fourier transform infrared (FT-IR), indicating that the existence of PAH and rapid growth of crystal nuclei were essential for the formation of the Pt–Pd ANFs. The electrocatalytic activity and stability of the Pt–Pd ANFs for the oxygen reduction reaction (ORR) were investigated by rotating disk electrode voltammetry in 0.1 M HClO4 solution. The electrochemical tests indicated the {111}-enclosed Pt–Pd ANFs exhibited superior ORR activity along with satisfactory stability and methanol-tolerant ability under acidic conditions, which made them promising electrocatalysts for the future.

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 %).