Boosting reactivity of water-gas shift reaction by synergistic function over CeO2-x/CoO1-x/Co dual interfacial structures

Dual-interfacial structure within catalysts is capable of mitigating the detrimentally completive adsorption during the catalysis process, but its construction strategy and mechanism understanding remain vastly lacking. Here, a highly active dual-interfaces of CeO2-x/CoO1-x/Co is constructed using the pronounced interfacial interaction from surrounding small CeO2-x islets, which shows high activity in catalyzing the water-gas shift reaction. Kinetic evidence and in-situ characterization results revealed that CeO2-x modulates the oxidized state of Co species and consequently generates the dual active CeO2-x/CoO1-x/Co interface during the WGS reaction. A synergistic redox mechanism comprised of independent contribution from dual functional interfaces, including CeO2-x/CoO1-x and CoO1-x/Co, is authenticated by experimental and theoretical results, where the CeO2-x/CoO1-x interface alleviates the CO poison effect, and the CoO1-x/Co interface promotes the H2 formation. The results may provide guidance for fabricating dual-interfacial structures within catalysts and shed light on the mechanism over multi-component catalyst systems.

Promoting Molecular Exchange on Rare-Earth Oxycarbonate Surfaces to Catalyze the Water-Gas Shift Reaction

It is highly desirable to fabricate an accessible catalyst surface that can efficiently activate reactants and desorb products to promote the local surface reaction equilibrium in heterogeneous catalysis. Herein, rare-earth oxycarbonates (Ln₂O₂CO₃, where Ln = La and Sm), which have molecular-exchangeable (H₂O and CO₂) surface structures according to the ordered layered arrangement of Ln₂O₂²⁺ and CO₃^2- ions, are unearthed. On this basis, a series of Ln₂O₂CO₃-supported Cu catalysts are prepared through the deposition precipitation method, which provides excellent catalytic activity and stability for the water-gas shift (WGS) reaction. Density functional theory calculations combined with systematic experimental characterizations verify that H₂O spontaneously dissociates on the surface of Ln₂O₂CO₃ to form hydroxyl by eliminating the carbonate through the release of CO₂. This interchange efficiently promotes the WGS reaction equilibrium shift on the local surface and prevents the carbonate accumulation from hindering the active sites. The discovery of the unique layered structure provides a so-called "self-cleaning" active surface for the WGS reaction and opens new perspectives about the application of rare-earth oxycarbonate nanomaterials in C1 chemistry.

An air-stable, reusable Ni@Ni(OH)2 nanocatalyst for CO2/bicarbonate hydrogenation to formate

Production of formate via CO2/bicarbonate hydrogenation using cheap metal-based heterogeneous catalysts is attractive. Herein, we report the organometallic synthesis of a foam-like Ni@Ni(OH)2 composite nanomaterial which exhibited remarkable air stability and over 2 times higher catalytic activity than commercial RANEY® Ni catalyst in formate synthesis. Formate generation was achieved with an optimal rate of 6.0 mmol gcat-1 h-1 at 100 °C, a significantly lower operation temperature compared to the 200-260 °C reported in the literature. Deep characterization evidenced that this nanomaterial was made of an amorphous Ni(OH)2 phase covering metallic Ni sites; a core-shell structure which is crucial for the stability of the catalyst. The adsorption of bicarbonates onto the Ni@Ni(OH)2 catalyst was found to be a kinetically relevant step in the reaction, and the Ni-Ni(OH)2 interface was found to be beneficial for both CO2 and H2 activation thanks to a cooperative effect. Our findings emphasize the underestimated potential of Ni-based catalysts in CO2 hydrogenation to formate, indicating a viable strategy to develop stable, cheap metal catalysts for greener catalytic applications.

Facile Fabrication of CeO2-Al2O3 Hollow Sphere with Atomically Dispersed Fe via Spray Pyrolysis

A facile spray pyrolysis method is introduced to construct the hollow CeO₂-Al₂O₃ spheres with atomically dispersed Fe. Only nitrates and ethanol were involved during the one-step preparation process using the ultrasound spray pyrolysis approach. Detailed explorations demonstrated that differences in the pyrolysis temperature of the precursors and heat transfer are crucial to the formation of the hollow nanostructure. In addition, iron species were in situ atomically dispersed on the as-formed CeO₂-Al₂O₃ hollow spheres via this strategy, which demonstrated promising potential in transferring syn-gas to valuable gasoline products.

Direct Identification of Active Surface Species for the Water-Gas Shift Reaction on a Gold-Ceria Catalyst

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.

Pt-Embedded CuO x-CeO2 Multicore-Shell Composites: Interfacial Redox Reaction-Directed Synthesis and Composition-Dependent Performance for CO Oxidation

Exploring the state-of-the-art heterogeneous catalysts has been a general concern for sustainable and clean energy. Here, Pt-embedded CuO _x-CeO₂ multicore-shell (Pt/CuO _x-CeO₂ MS) composites are fabricated at room temperature via a one-pot and template-free procedure for catalyzing CO oxidation, a classical probe reaction, showing a volcano-shaped relationship between the composition and catalytic activity. We experimentally unravel that the Pt/CuO _x-CeO₂ MS composites are derived from an interfacial autoredox process, where Pt nanoparticles (NPs) are in situ encapsulated by self-assembled ceria nanospheres with CuO _x clusters adhered through deposition/precipitation-calcination process. Only Cu-O and Pt-Pt coordination structures are determined for CuO _x clusters and Pt NPs in Pt/CuO _x-CeO₂ MS, respectively. Importantly, the close vicinity between Pt and CeO₂ benefits to more oxygen vacancies in CeO₂ counterparts and results in thin oxide layers on Pt NPs. Meanwhile, the introduction of CuO _x clusters is crucial for triggering synergistic catalysis, which leads to high resistance to aggregation of Pt NPs and improvement of catalytic performance. In CO oxidation reaction, both Pt^δ+-CO and Cu⁺-CO can act as active sites during CO adsorption and activation. Nonetheless, redundant content of Pt or Cu will induce a strongly bound Pt-O-Ce or Cu-[O _x]-Ce structures in air-calcinated Pt/CuO _x-CeO₂ MS composites, respectively, which are both deleterious to catalytic reactivity. As a result, the composition-dependent catalytic activity and superior durability of Pt/CuO _x-CeO₂ MS composites toward CO oxidation reaction are achieved. This work should be instructive for fabricating desirable multicomponent catalysts composed of noble metal and bimetallic oxide composites for diverse heterogeneous catalysis.

Synthesis of a ceria-supported iron–ruthenium oxide catalyst and its structural transformation from subnanometer clusters to single atoms during the Fischer–Tropsch synthesis reaction

The transformation from subnanometer clusters to single atoms during Fischer–Tropsch synthesis was revealed by X-ray absorption fine structure analysis of a ceria-supported iron–ruthenium oxide catalyst.

Study of the sludge reduction in an oxic-settling-anaerobic activated sludge process based on UNITANK

An oxic-settling-anaerobic process (OSA) can effectively reduce sludge production, but most of the research studies on the OSA process have been either under laboratory test conditions or based on synthetic wastewater, which cannot fully reflect the performance and sludge reduction efficiency in existing OSA process. Thus, aiming at examining the sludge reduction efficiency and the stability of the OSA process, UNITANK and UNITANK-OSA processes were performed in a 120 m(3)/d pilot-scale system using actual sewage. The results indicate that UNITANK-OSA achieved a 48% reduction of the sludge compared to the reduction due to UNITANK, not considering the accumulation of the effluent-suspended solids. The effluent quality was not found to change significantly, except that the total phosphorus concentration increased slightly. The extracellular polymeric substances metal floc theory may, to some extent, explain this reduction in this study. The OSA process could be used to reform the classic wastewater treatment process to get lower sludge mass.

[Visual symptoms of sellar tumors: a report of 407 cases]

The common primary symptoms of sellar tumors are visual impairment and field defects associated with the anatomic relationship between the sella turcica and the visual route, and the patients often consult the oculist first. The authors reviewed 407 cases of sellar tumors at their hospital during the recent 10 years and analyzed the characteristics of these patients to present the general clinical patterns and main points for diagnosis of this disease.

Improved myocardial protection by antegrade perfusion in combination with coronary sinus occlusion in the presence of left anterior descending artery obstruction

The present study was undertaken to evaluate the improved protection of antegrade aortic root perfusion combined with intermittent coronary sinus occlusion (APCSO) for the 1-hour ischemic myocardium in the presence of left anterior descending artery occlusion, 12 dogs were divided into 2 groups: anteperfusion (AP) alone (n = 6) and APCSO (n = 6). The experimental results showed that APCSO provided a better cardioplegic distribution and a lower hypothermia (15.6 degrees C versus 17.2 degrees C) in the occluded LAD region, compared with AP. After ischemia, cardiac index and left ventricular stroke index recovered excellently in APCSO (128% to 141% and 115% to 158% of preischemic values, respectively), and much worse in AP (69% to 82% and 53% to 73% of preischemic values, respectively). Our study has confirmed that APCSO is superior to AP in myocardial protection in the presence of coronary artery occlusion.