Search

Comprehensive Summary: As the promising catalysts for the water‐gas shift (WGS) reaction, the activity of Au‐CeO2 composites is susceptible to the aggregation size and electronic state of Au species. Previous reports were extensively focused on the discrepancy between nonmetallic Au and metallic Au nanoparticles, whereas the understanding of the authentic role of the isolated Au atoms was limited. Herein, we investigated the catalytic behavior and structural information over two types of Au/CeO2 catalysts, in which the predominant conjunctions were isolated Au1‐CeO2 and Aun‐CeO2, respectively. Based on comprehensive characterizations, particularly by in‐situ Raman and in‐situ DRIFTS, we found that the isolated Au atoms were responsible for enhancing the reducibility of the CeO2 matrix. The CO adsorption ability on the isolated Au sites was significantly inferior to clustered Au atoms, especially at relatively high temperatures (> 200 °C). As a result, the boosted O vacancy on the isolated Au1‐CeO2 conjunctions could improve the H2O activation ability for the Au‐CeO2 catalysts and demonstrate a comparable activity to the clustered Aun‐CeO2 sites. This work might deepen understanding of the catalytic function for the isolated Au1 site within Au/CeO2 systems while catalyzing the WGS reaction. [ABSTRACT FROM AUTHOR]

The oxides and active metals at the interface synergistically activate reactants and thus promote the reaction, but the interface structure often changes dynamically during the reaction. In the conventional supported catalysts, the metals at the interface have been extensively studied, while the structural evolution of oxides is often overlooked due to the interference of the bulk phase signal. In this work, CeO2−CuO inverse catalysts are designed to reveal the dynamic structure evolution of CeO2 in the CeO2−CuO system during the water gas shift (WGS) reaction by in situ Raman, in situ XRD, quasi in situ XPS, and near ambient pressure XPS (NAP‐XPS). CeO2 is partially concealed in the CuO phase in the un‐pretreated catalyst and gradually exposed to the surface, forming an inverse CeOx/Cu structure during the reducing process. This structure exhibits a high catalytic activity in the WGS reaction and remains durable under the reductive conditions. When the inverse CeOx/Cu structure is exposed to the non‐redox conditions, the reconfiguration of the reduced oxide is observed which is caused by the oxygen migration of CeO2. This work explores the structure evolution of CeO2 in CeO2−CuO inverse catalyst under different conditions by in situ characterization technique and provides a reference for monitoring the dynamic changes of oxide structure. [ABSTRACT FROM AUTHOR]

Ammonia is a promising hydrogen storage medium, and the catalytic decomposition of ammonia offers a route to clean hydrogen generation. Constructing efficient multicomponent catalysts with an appropriate choice of components is a feasible strategy to enhance the catalytic performance in ammonia decomposition. In this work, a series of multicomponent Ni–Y2O3–Al2O3 catalysts with a unique internal hollow spherical structure were synthesized by a facile aerosol-assisted self-assembly approach. Compared with the Ni–Y2O3 and Ni–Al2O3 catalysts, the Ni–Y2O3–Al2O3 catalysts exhibited a significant advantage in the catalytic performance of ammonia decomposition, and their activity remained stable during tests up to 100 h under very harsh reaction conditions (550 °C and space velocity of 60,000 mL·gcat–1·h–1), outperforming almost all Ni-based catalysts reported so far. Systematic characterizations demonstrated that Y2O3 effectively dispersed Ni nanoparticles, alleviated the poisoning effect of H2 on the catalysts, and provided sufficient basic sites to improve the catalytic activity. In addition, the introduction of Al2O3 further inhibited the aggregation of Ni and Y2O3 nanoparticles and maintained their high dispersion in the reaction. This work elucidates the contribution of different compositions in multicomponent catalysts and provides a strategy for the construction of efficient Ni-based ammonia decomposition catalysts. [ABSTRACT FROM AUTHOR]

As a class of nanomaterials with natural enzyme-like characteristics, nanozymes have shown their great potential in various applications. Reducible metal oxides featured with defect structures, and single-atom catalysts with isolated metal sites are regarded as two of the most promising nanozymes. However, the strategies to construct highly performed nanozymes by combining these advantages are rarely reported. Herein, we report the coordination-unsaturated single-atomic Cu species supported on sintered CeO2, which combines the advantages of defect engineering and single-atom catalysis, exhibiting a largely enhanced peroxidase (POD)-like activity. The high-temperature calcination induces the transformation of inert Cu1O4 species into coordination-unsaturated Cu1O3 sites. This novel Cu1O3 active sites with an unsaturated coordination work as a new type of defect sites to greatly activate the isolated Cu atoms and accelerate the dissociation of H2O2 to form hydroxyl radicals (·OH). The obtained nanozyme with a high POD-like activity possesses low cytotoxicity, showing potential applications for the tumor inhibition in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Highly efficient oxide–metal interfaces in solid catalysts play a crucial role in numerous heterogeneous catalysis applications. In this work, an active and stable interface is fabricated between Ni and CeO2 nanoparticles, which are stabilized using an Al2O3 support, and it enormously boosts the catalytic performance for the NH3 decomposition reaction. Systematic characterizations demonstrate that the small CeO2 nanoparticles on the Al2O3 support optimize the dispersion of Ni nanoparticles and modulate the reducibility of the interfacial Ni atoms, which directly correlate with the enhancement of the catalytic reactivity and stability. Moreover, in situ Raman and TPR results illustrate that the abundant surface-defective structure over small CeO2 nanoparticles augments the adsorption and activation sites of NH3 molecules for the Ni-CeOx/Al2O3 catalyst. This work deepens the understanding of the synergistic effect between active metal and oxides and provides a facile strategy for designing efficient NH3 decomposition catalysts. [ABSTRACT FROM AUTHOR]