Zumin Wang

Efficient water oxidation under visible light by tuning surface defects on ceria nanorods

Fluorite CeO2 nanorods (NRs) with tunable surface defects are successfully prepared via hydrothermal synthesis followed by post-calcination under different atmospheres. Impressively, the CeO2 NRs obtained under mixed Ar and H-2 gas at 800 degrees C exhibit superior catalytic activity towards water oxidation under visible light (lambda >= 420 nm), which is 10 times higher than that of CeO2 NRs treated under air at 800 degrees C. Detailed characterization and theoretical analysis reveal that the rich surface defects including surface oxygen vacancies and Ce3+ ions are the origin of the enhanced water oxidation performance of the CeO2 NRs treated under the reduced atmosphere.

Bismuth oxychloride hollow microspheres with high visible light photocatalytic activity

Hollow microspheres of two bismuth oxychlorides, BiOCl and Bi24O31Cl10, were successfully synthesized using carbonaceous microsphere sacrificial templates. The phase evolution from BiOCl to Bi24O31Cl10 was easily realized by heating the former at 600 °C. With a uniform diameter of about 200 nm, an average shell thickness of 40 nm, and basic nanosheets of <20 nm, the hollow microspheres of both BiOCl and Bi24O31Cl10 showed high visible light photocatalytic activity towards the degradation of Rhodamine B (RhB). Besides the effective photosensitization process and efficient photointroduced carrier separation, the high photocatalytic activity was believed to result from their hollow-structure-dependent large visible light absorption. Moreover, as a chlorine-deficient analogue, the Bi24O31Cl10 hollow spheres possessed a narrower band gap, more dispersive band structure, and higher photocarrier conversion efficiency, which further helped them to exhibit better photocatalytic activity.

Y2O3:Yb3+/Er3+ Hollow Spheres with Controlled Inner Structures and Enhanced Upconverted Photoluminescence

Multishell Y2 O3 :Yb(3+) /Er(3+) hollow spheres with uniform morphologies and controllable inner structures are prepared successfully by using a glucose-template hydrothermal process followed by temperature-programmed calcination. Much enhanced upconverted photoluminescence of these Y2 O3 :Yb(3+) /Er(3+) are observed, which are due to the multiple reflections and the enhanced light-harvesting efficiency of the NIR light resulting from the special features of the multishell structures.

Composite Yttrium-Carbonaceous Spheres Templated Multi-Shell YVO4 Hollow Spheres with Superior Upconversion Photoluminescence

Complex oxide YVO4 multi-shell hollow spheres with uniform morphologies and controllable shell numbers are successfully prepared by using a newly developed and general composite yttrium-carbonaceous sphere templated approach. The prominent upconversion luminous intensity of the YVO4 :Yb3+ /Er3+ hollow spheres might be attributed to the enhanced near-infrared excitation light harvesting efficiency originated from the multiple reflections.

Highly active CeO 2 hollow-shell spheres with Al doping

Metal oxide hollow structures are of great interest in many current and emerging areas of technology. This paper presents a facile and controlled protocol for the synthesis of Al-doped CeO2 hollow-shell spheres (CHS), where the dopant confers enhanced stability and activity to the material. These Al-doped CeO2 hollow-shell spheres (ACHS) possess a controllable shell number of up to three, where the sizes of the exterior, middle, and interior spheres were about 250‒100 nm,150‒50 nm, and 40‒10 nm, respectively, and the average shell thickness was ~15 nm. The thermal stability of the ACHS structure was enhanced by the homogeneous incorporation of Al atoms, andmore active oxygen species were present compared with those in the non-doped congener. Au NPs supported on ACHS (Au/ACHS) showed superior catalytic performance for the reduction of p-nitrophenol. For the same Au NP content, the reaction rate constant (k) of the Au/ACHS was nearly twice that of the non-doped Au/CHS, indicating that Al doping is promising for improving the performance of inert or unstable oxides as catalyst supports.摘要本文利用多孔碳球为模板, 通过竞争吸附控制煅烧法制备了铝掺杂的氧化铈多壳层空心球材料. 通过XRD、SEM、TEM对所得材料的结构、表面形貌以及热稳定性能进行了表征, 结果表明该方法制备的不同掺杂比例的多壳层空心球均一分散, 铝原子被均匀地分布到氧化铈的晶格中, 使其热稳定性得到提高. XPS结果表明铝的掺杂大大提高了材料中三价铈和表面氧空位的比例, 所以当其被作为催化剂载体时, 负载的金纳米粒子更加分散且与载体结合作用更强. 将该催化剂应用于硝基苯酚加氢反应, 其催化活性比未掺杂铝的样品提高了一倍.本文研究结果表明铝掺杂可以有效提高氧化铈催化剂的稳定性和活性; 竞争吸附控制煅烧法是制备空心掺杂材料的一种简单实用的方法.

Controlled synthesis of highly active Au/CeO2 nanotubes for CO oxidation

Uniform CeO2 nanotubes with smooth thin walls and high porosity were controllably synthesized using a simple well-controlled solvothermal technique. The growth of CeO2 nanotubes was explored and it was found that it followed the oriented attachment-Ostwald ripening mechanism. Furthermore, through an auto-redox process, gold nanoparticles of ∼5 nm size could be homogeneously generated on these CeO2 nanotubes. These novel nanocomposites exhibited outstanding performance in terms of both activity and stability for catalytic CO oxidation.

Facile one-pot synthesis of MOF supported gold pseudo-single-atom catalysts for hydrogenation reactions

Catalysts based on extremely small (single atoms or pseudo single atoms) noble metals can lead to much more efficient use through enhanced reactivity and selectivity. However, fabrication of practical and stable (pseudo) single-atom catalysts on various supports remains a significant challenge. Herein, we report a facile co-precipitation and conversion strategy to fabricate a series of gold pseudo single-atom supported metal organic framework catalysts (PSAC Au/MOF) on a large scale. By well controlled synthesis of precursors, up to 1.0 wt% surface clean Au atoms can be atomically dispersed and stabilized on the support. The PSAC Au/MOF exhibited superior catalytic activity in hydrogenation of p-nitrophenol, exceeding the turnover frequency of most reported catalysts by more than one order of magnitude. No obvious decline in activity was observed after 5 cycles.