负载型贵金属纳米粒子作为光/超声催化剂在化学合成和降解污染物方面的应用

综述了Au/TiO2、Au/ZrO2、Ag/AgCl等负载型贵金属纳米粒子作为有效的光/超声催化剂在化学合成和降解污染物方面的应用.负载型贵金属纳米粒子能够有效地将太阳能转化为化学能.在紫外光或可见光的辐照下,负载型贵金属纳米粒子能够催化一系列的选择性化学转化,如醇类化合物氧化为醛/酮类化合物、硫醇氧化为二硫化合物、苯氧化为苯酚、硝基苯类化合物还原为偶氮化合物等.在超声波辐射下,负载型贵金属纳米粒子能够有效地催化分解水产氢.此外,在紫外光或可见光的辐照下,负载型贵金属纳米粒子能够有效地催化降解多种污染物,如醛类、醇类、酸类、酚类化合物和染料等.在超声波辐射下,负载型贵金属纳米粒子也能够有效地催化降解包括染料在内的有机污染物.

Superacid Catalyst SO4^2-/ZrO2-La2O3 Prepared by Ultrasonic Co-precipitation and Low Temperature Aging

Sulfated zirconia-lanthana （SO4^2-/ZrO2-La2O3） precursors were prepared by ultrasonic coprecipitation method and followed by aging at different temperature. The precursors were treated by 0.5 mol/L H2SO4. Samples of SO4^2-/ZrO2-La2O3 nano-crystalline catalysts were obtained by baking the treated precursors at different temperatures. The acidic properties of SO4^2-/ZrO2-La2O3 were tested by the Hammett indicator method. The phase composition, specific area, particle structure, and surface state were characterized by X-ray diffraction, BET, transmission electron microscopy, infrared spectrum, and X-ray photoelectron spec- troscopy. The catalytic activities were estimated by esterification of acetic acid with glycerin. It was shown that the catalyst prepared by ultrasonic stirring and low temperature （-15 ℃） exhibited highly active sites and high catalytic property.

Influence of ultrasonic on the coking amount of catalyst （Ni/γ-Al2O3） for the dry reforming of benzene

The Influence of ultrasonic treatment on the coking amount of a nickel-based catalyst （Ni/γ-Al2O3） for the reaction of reforming with carbon dioxide of Benzene was investigated. The results show that ultrasonic treatment modify the pore size distribution of the catalysts significantly and also reduce the amount of coke formed on the catalyst. The reduction in the coking amount is not sensitive to the power output of the ultrasonic treatment device in the power range tested （120 W and 500 W）.

Cobalt/iron bimetal-organic frameworks as efficient electrocatalysts for the oxygen evolution reaction

The development of high efficiency and stable electrocatalysts for oxygen evolution is critical for energy storage and conversion systems. Herein, a series of Co/Fe bimetal-organic frameworks (MOFs) were fabricated using a facile ultrasonic method at room temperature, as electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. The Co2Fe-MOF exhibited an overpotential of 280 mV at a current density of 10 mA cm^-2, a low Tafel slope of 44.7 mV dec^-1, and long-term stability over 12000 s in 1 mol L^-1 KOH. This impressive performance was attributed to the high charge transfer rate, large specific surface area, and synergistic effects of the cobalt and iron centers.

Mass production of high-performance single atomic FeNC electrocatalysts via sequenced ultrasonic atomization and pyrolysis process

Mass production of highly efficient,durable,and inexpensive single atomic catalysts is currently the major challenge associated with the oxygen reduction reaction(ORR)for fuel cells.In this study,we develop a general strategy that uses a simple ultrasonic atomization coupling with pyrolysis and calcination process to synthesize single atomic FeNC catalysts(FeNC SACs)at large scale.The microstructure characterizations confirm that the active centers root in the single atomic Fe sites chelating to the four-fold pyridinic N atoms.The identified specific Fe active sites with the variable valence states facilitate the transfer of electrons,endowing the FeNC SACs with excellent electrochemical ORR activity.The FeNC SACs were used as cathode catalysts in a homemade Zn-air battery,giving an open-circuit voltage(OCV)of 1.43 V,which is substantially higher than that of commercial Pt/C catalysts.This study provides a simple approach to the synthesis of single atomic catalysts at large scale.

Pd embedded in porous carbon （Pd@CMK-3） as an active catalyst for Suzuki reactions： Accelerating mass transfer to enhance the reaction rate

Heterogeneous catalysts are promising candidates for use in organic reactions due to their advantages in separation, recovery, and environment compatibility. In this work, an active porous catalyst denoted as Pd embedded in porous carbon （Pd@CMK-3） has been prepared by a strategy involving immersion, ammonia- hydrolysis, and heating procedures. Detailed characterization of the catalyst revealed that Pd（0） and Pd（I1） species co-exist and were embedded in the matrix of the porous carbon （CMK-3）. The as-prepared catalyst has shown high activity toward Suzuki reactions. Importantly, if the reaction mixture was homogenized by two minutes of ultrasonication rather than magnetic stirring before heating, the resistance to mass transfer in the pore channels was significantly reduced. As a result, the reactions proceeded more rapidly and a four-fold increase in the turnover frequency （TOF） could be obtained. When the ultrasonication was employed throughout the entire reaction process, the conversion could also exceed 90% even without the protection of inert gas, and although the reaction temperature was lowered to 30 ℃. This work provides a method for fabricating highly active porous carbon encapsulated Pd catalysts for Suzuki reactions and proves that the problem of mass transfer in porous catalysts can be conveniently resolved by ultrasonication without any chemical modification being necessary.