金属铂氧化物还原反应温度的模拟研究

采用第一性原理的分子动力学对H_(2)和金属铂氧化物的还原反应温度进行了模拟计算,同时对其反应机理进行了探讨。计算结果表明,从减少能耗的角度出发,金属铂氧化物还原反应发生的适合温度在250℃左右。PtO_(2)的还原反应路径有两条:一是由H_(2)先还原为PtO,再进一步还原为金属Pt;另外一种路径是PtO_(2)由H2直接还原为金属Pt,反应路径的选择与反应压力有关。PtO还原为Pt的活化能垒高于PtO_(2)还原为金属Pt的活化能垒,其原因是PtO与H_(2)的反应轨道能级差高于PtO_(2)与H_(2)的反应轨道能级差,因此PtO与H_(2)间电子跃迁所需要的能量要高于PtO_(2)与H_(2)。

现场拉曼光谱研究多种铂氧化物还原过程及其对甲醇氧化的影响

采用原位拉曼光谱技术研究方波电位循环氧化还原 (ORC)过程中产生的铂氧化物的还原过程 ,其中过氧化物和超氧化物消失的电位在 0 2V左右 ,晶格氧化物和氧化铂则分别消失在 0V和 -0 2 5V左右。

直热式钽基铂网氧化物灯丝特性的研究

阐述了钽基铂网氧化物灯丝的工作机理、性能、制造工艺。对其放电特性的研究表明该灯丝性能良好、工作稳定可靠、放电波形平整而光滑。在１１００Ｋ工作温度时，灯丝发射电流密度超过６Ａ／ｃｍ２，四根这种灯丝可产生３５０Ａ弧流（脉冲宽度３０ｍｓ）。

铂系金属氧化物对增强Al_2O_3热稳定性作用的研究

为探索铂金属氧化物(以下均用MO_(x)代表)对增强栽体Al_2O_3热稳定性作用的机理,本文采用了氮物理等温吸附、X-射线物相分析、电子探针及附栽催化剂的活性试验等多种方法,研究了Al_2O_3和MO_(x)-Al_2O_3两种物系的物理和化学性质,认为MO_(x)对增强载体Al_2O_3热稳定性的作用,主要是通过MO_(x)与Al_2O_3间存在较强的相互作用、从而提高了Al^(3+)和O^(-2)的扩散活化能,在一定程度上抑制了它们间的互扩散,此外在加热过程中,Al_2O_3晶界间将偏析出MO_(x)晶粒而提高了Al_2O_3晶粒迁移所需越过的能垒,从而形成了Al_2O_3晶粒间的碰撞障碍,有效地防止其进一步的聚集。

Mg3(PO4)2修饰铂钨锆复合氧化物的性能

采用浸渍-焙烧法制备不同含量Mg3(PO4)2修饰的铂钨锆复合氧化物(Pt-WO3/ZrO2)。采用N2吸附-脱附、X线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、NH3程序升温脱附(NH3-TPD)、H2程序升温还原(H2-TPR)以及CO脉冲吸附等手段对Mg3(PO4)2修饰的Pt-WO3/ZrO2进行表征。通过连续的固定床反应器对Mg3(PO4)2修饰的Pt-WO3/ZrO2催化甘油氢解的稳定性能进行评价,并利用水热釜对修饰前后的WO3/ZrO2载体进行水热稳定性研究。结果表明:一定量Mg3(PO4)2修饰的Pt-WO3/ZrO2,ZrO2的四方相较单斜相增长较多,总酸量增加,Pt的分散度增大,金属的还原性能增强,其中2%Mg3(PO4)2修饰的Pt-WO3/ZrO2催化甘油氢解的稳定性能较为显著,200 h内反应基本趋于稳定。一定量Mg3(PO4)2的引入有效地促进了ZrO2晶型的转变,促使其他晶型的ZrO2更多地转变为四方相的ZrO2,阻止了WO3/ZrO2载体总酸量的降低和孔道结构的坍塌,从而提高了WO3/ZrO2载体的水热稳定性。

Pt/CeO_2-ZrO_2催化剂上的CO变换反应本征动力学

The intrinsic kinetics of water gas shift reaction over Pt/CeO 2-ZrO 2 was investigated.Experiments were carried out by means of orthogonal design.Parameters of power-type rate model of water gas shift reaction were determined by the non-linear least-square parameter estimation method.The kinetics of water gas shift reaction over Pt/CeO 2-ZrO 2 was different from that of common commercial catalysts.The accuracy of experimental data and kinetics model was proved by F-examination.

Comparative studies of leached Pt-Fe and Pt-Co catalysts for CO oxidation reactions

Leached Pt-Fe and Pt-Co catalysts were prepared by acid leaching the reduced catalysts in acid solution. Oxidation treatments of leached catalysts produced the structure o f metal oxides decorat-ing the surface of nanoparticles. The fully oxidized Fe2O3 and Co3O4 species on Pt nanoparticle sur-faces result in the low performance of the CO complete oxidation （COOX） reaction. In contrast, un-saturated FeO and CoO surface species can be formed during exposure to the CO preferential oxida-tion （CO-PROX） reaction with an excess of H2, leading to a high O2 activation ability and enhancing the CO-PROX activity. The FeOx surface structures can be transformed between these two states by varying the reactive gas environments, exhibiting oscillating activity in these two reactions. Con-versely, the CoO surface structure formed in the H2 -rich atmosphere is stable when exposed to the COOX reaction and exhibits similar activity in these two reactions. It is hoped that this work may assist in understanding the important role of surface oxides in real reactions.

Effects of hierarchical structure on the performance of tin oxide-supported platinum catalyst for room-temperature formaldehyde oxidation

Flower-like tin oxide-supported platinum（Pt/SnOx） with a hierarchical structure was synthesized by a hydrothermal method and characterized by XRD,SEM,TEM,high resolution TEM,XPS and nitrogen adsorption.The flower-like Pt/SnOx microspheres of 1 μm in diameter were composed of staggered petal-like nanosheets with a thickness of 20 nm.Pt nanoparticles（NPs） of 2-3 nm were well dispersed on the SnOx nanosheets.The catalyst was tested in the catalytic oxidation of gaseous formaldehyde（HCHO） at room temperature,and exhibited enhanced activity compared to Pt NPs supported on commercial SnO and ground SnOx.HCHO removal of 87%was achieved over the hierarchical Pt/SnOx after 1 h of reaction,which was 1.5 times that over the ground SnOx-supported Pt（Pt/g-SnOx）,and the high activity was maintained after six recycles,showing the high stability of this catalyst.HCHO decomposition kinetics was modeled as a second order reaction.The reaction rate constant for Pt/SnOx was 5.6 times higher than Pt/g-SnOx.The hierarchical pore structure was beneficial for the diffusion and adsorption of HCHO molecules,and the highly dispersed Pt NPs on the SnOx nanosheets were the active sites for the oxidative decomposition of HCHO into CO2 and H2O.This study provided a promising approach for designing efficient catalysts for indoor HCHO removal at ambient temperature.

Glycerol hydrogenolysis to n‐propanol over Zr‐Al composite oxide‐supported Pt catalysts

Zr‐Al mixed oxide supported Pt catalysts with different Zr/Al mole ratios（2.5%Pt/ZrxAl（1–x）Oy） were synthesized by an impregnation method and used for the selective hydrogenolysis of glycerol to n‐propanol in an autoclave reactor. The catalysts were fully characterized by X‐ray powder diffrac‐tion, Brunauer‐Emmett‐Teller surface area analysis, CO chemisorption, H2 temperature‐ pro‐grammed reduction, pyridine‐infrared spectroscopy, and NH3‐temperature‐programmed desorp‐tion. The results revealed that the Zr/Al ratio on the support significantly affected the size of the platinum particles and the properties of the acid sites on the catalysts. The catalytic performance was well correlated with the acidic properties of the catalyst; specifically, more acid sites contrib‐uted to the conversion and strong acid sites with a specific intensity contributed to the deep dehy‐dration of glycerol to form n‐propanol. Among the tested catalysts, 2.5 wt% Pt/Zr（0.7）Al（0.3）Oy exhibited excellent selectivity for n‐propanol with 81.2% glycerol conversion at 240 °C and 6.0 MPa H2 pres‐sure when 10% aqueous glycerol solution was used as the substrate. In addition, the effect of vari‐ous reaction parameters, such as H2 content, reaction temperature, reaction time, and number of experimental cycles were studied to determine the optimized reaction conditions and to evaluate the stability of the catalyst.

Attenuation of cisplatin induced ototoxicity by sound preonditioning through NO pathway

Objective：To explore the protective effect of sound preconditioning against ototoxicity induced by cisplatin and its possible mechanism with respect to the nitric oxide （NO） pathway. Methods： Albino guinea pigs were divided into silent control, CDDP,sound preconditioning and sound preconditioning＋CDDP groups. The animals of the CDDP group were injected with cisplatin intravenously 8 mg/kg b.w. The animals in the sound preconditioning were exposed to white noise at 85dB SPL, 5h/d, for 10 d （sound preconditioning）. The animals in the sound preconditioning＋CDDP group were treated with sound preconditioning first and then administrated with cisplatin intravenously 8 mg/kg b.w. Hearing thresholds of auditory brainstem responses （ABRs） of all animals were measured to evaluate hearing function. Hair cell loss was estimated via surface preparation. Cochlear tissue was assayed for measurement of NO level and immunohistochemistry method was used for inducible nitric oxide synthase （iNOS） analysis. Results： There was no significant difference between the silent control and sound preconditioning animals with respect to either functional or histological measures. Among the animals in the CDDP group, there was a significant elevation of threshold at the high test frequencies after administration compared with the silent control group （P〈0. 05）. Morphological examination showed that there was obvious loss of the OHC, especially in the third row of the basal turn. The NO level and immunoreactivity to iNOS in this group were higher and more intensive than those of the silent control group （P〈0. 05）. The ABR thresholds in the sound preconditioning ＋ CDDP group were much lower than those of the CDDP group （P〈0.05）. Slight sporadic loss of OHC was found in this group. The immunoreactivity to iNOS and the level of NO in cochlea decreased significantly compared with the CDDP group （P〈 0. 05）. Conclusion： It is suggested that sound preconditioning, to some extent, provides protective effect against ototoxicity of cisplatin. The excess synthesis of NO induced by the over-expressed of iNOS may be involved in the CDDP induced ototoxicity. The possible mechanism is related to suppression of the NO pathway.

Investigation of flexible electrodes modified by TiN,Pt black and IrO_x

TiN, platinum （Pt） black and iridium oxide are introduced to the stimulating sites to improve the performance of the flexible electrode. Low temperature process is used to fabricate the modifying films. TiN is coated on the gold sites by magnetron sputtering while platinum black and iridium oxide are coated by electroplating and electrodeposifion, respectively. The impedance of the electrode decreases dramatically after modification. The combined analysis of surface morphology and cyclic voltammograms （CV） in phosphate buffer saline （PBS） solution indicates that the modified electrode sites have larger electrode-electrolyte capacitance and smaller faradic resistance than unmodified sites, thus they have smaller electrochemical impedances.

A DFT study on PtMo resistance to SO_2 poisoning

Pt is a catalyst in proton exchange membrane fuel cell （PEMFC）, and its activity will be degraded in the air due to the exist- ence of SOx impurities. On strategy is introducing of Mo into the Pt catalyst because it can improve the SOx-tolerance capacity. Based on the aforementioned phenomenon, a density function theory （DFT） study on SOx adsorbed on Pt（111） and PtMo（111） was performed to enhance Pt catalytic activity. The adsorption energy of adsorbed species, the net change, partial density of state （PDOS）, and d-band center were calculated and analyzed comparatively. The results show that the presence of Mo-atom weakens the S-Pt bond strength and reduces the adsorption energies for SO2, S and SO3 on PtMo（111）. Moreover, the Mo atom weakens the effects of SO2 on the PtMo（lll） electronic structure and makes the catalyst maintains its original electronic structure after SO2 adsorption as compared with Pt（111）.

New cyclometalated transition-metal based photosensitizers for singlet oxygen generation and photodynamic therapy

The aim of this review article is to introduce recent studies on an emergent class of singlet oxygen photosensitizers of potential applications to the photodynamic therapy,with a primary focus on the cyclometalated transition-metal complexes.Singlet oxygen photosensitization performances of various cyclometalated Ir and Pt scaffolds are reviewed,and the general photophysical properties of relevant systems and the mechanisms of singlet oxygen production via photo-sensitization are also briefly discussed.Thus far,investigations of singlet oxygen sensitization by such Ir and Pt complexes are mainly carried out in organic solvents and under non-physiological conditions,while some research efforts have been made at examining the feasibility of applying pertinent cyclometalated complexes to photodynamic therapy.

Visible light catalyzed aromatization of 1,3,5-triaryl-2-pyrazolines by platinum(Ⅱ) polypyridyl complex under oxidant-free condition

With visible light(λ=450 nm) irradiation of a catalytic amount of platinum(Ⅱ) terpyridyl complex, 1,3,5-triaryl-2-pyrazolines can be smoothly converted to their corresponding pyrazoles and hydrogen in quantitative yields with no use of any oxidant at room temperature.