Ceria–zirconia-supported rhodium catalyst for NOx reduction from coal combustion flue gases

The catalytic activities of ceria–zirconia mixed oxides Ce_xZr_1−xO₂ (x = 0.17, 0.62 and 0.8) rhodium catalysts were determined by isothermal steady-state experiments using a representative mixture of exhaust gases of coal combustion. Results show that all supports are active in deNO_x reaction in the presence of the mentioned gas mixture. However, their catalytic activity varies with the content of cerium and goes through a maximum for x = 0.62, leading to 27% NO_x consumption. The effect of rhodium on Ce_0.62Zr_0.38O₂ considerably improves the catalytic activity during the deNO_x process assisted by hydrocarbons. The rhodium addition decreases by about 34 °C the temperature of NO_x consumption, which goes up to 57%. A mechanism of hydrocarbon (HC) assisted reduction of NO is proposed on ceria–zirconia-supported rhodium catalysts. This mechanism is divided in three catalytic cycles involving (i) the oxidation of NO into NO₂, (ii) the reaction of NO₂ and the hydrocarbons leading to RNO_x species and C_xH_yO_z, and finally (iii) the decomposition of NO assisted by these latter C_xH_yO_z species.     

DMFC的PtRu-NdOx/C催化剂合成及性能

以NdOx作为助催化剂,采用浸渍还原法合成了不同原子比例的PtRu-NdOx/C催化剂。首先研究了不同还原温度对PtRu/C催化剂的电催化性能的影响。X射线衍射光谱法(XRD)和循环伏安测试结果表明:当还原温度为90℃时,合成出的催化剂粒度最小,对甲醇电氧化的催化性能也最好。其次,通过能量散射X射线谱(EDX)、XRD、透射电子显微镜法(TEM)和循环伏安法、计时电流法等测试手段,研究了不同n(Pt)∶n(Ru)∶n(Nd)原子比例对PtRu-NdOx/C催化剂性能的影响。实验结果表明:n(Pt)∶n(Ru)∶n(Nd)原子比为3∶3∶1时,合成出的催化剂电催化性能较好;而且Pt与Ru以合金形式存在,而Nd的氧化物则以无定形态存在,催化剂粒子分布均匀,平均粒径在2nm左右。     

电催化析氢催化剂研究进展

氢能热值高和环境友好性强等特点使其成为未来能源界最具发展潜力的能源之一。电催化析氢反应（hydrogen evolution reaction,HER）作为一种绿色、可持续的产氢方法成为近年来广泛研究的主题。发展高性能、低成本、高活性的析氢催化剂是目前该领域面临的主要挑战。本文总结了近年来高性能催化剂用于HER反应的进展,重点介绍HER反应的基本原理,评估HER催化剂催化性能的典型方法,过渡金属以及化合物、非金属催化剂以及单原子催化剂等电催化析氢催化剂的最新研究进展,系统讨论了催化活性与催化剂形态、结构、组成和合成方法之间的联系,并对催化剂的合成策略、活性位点的固有活性、如何提高活性中心的内在活性和活性位点的数量进行了展望。     

Characterizing electrocatalytic surfaces: Electrochemical and NMR studies of methanol and carbon monoxide on Pt/C

We use cyclic voltammetry (CV) on fuel cell electrodes to elucidate the important differences between adsorbates resulting from carbon monoxide adsorption and methanol adsorption onto commercial Pt/C electrocatalysts in a sulfuric acid electrolyte. Under open circuit conditions, methanol was found to adsorb preferentially onto the Pt sites associated with “strongly bound” hydrogen. The sites associated with “weakly bound” hydrogen adsorbed methanol more slowly. In the case of CO adsorption, which requires no adsorbate dehydrogenation, all adsorption sites showed similar affinity towards the adsorbate. Electrochemical oxidation of the adsorbates derived from both methanol and CO exposure exhibit slower oxidation when the adsorbate is associated with cubic-packed-like sites than from close-packed-steps and other sites. NMR of a ¹³CO-adlayer prepared by electrochemical adsorption from low concentration ¹³CH₃OH shows a lower NMR shift and smaller linewidth than the previously reported values for electrochemically adsorbed ¹³CO gas. These results are interpreted in terms of adsorbate motion on the electrocatalyst surface.     

直接甲醇燃料电池性能研究

以自制的PtRuMo/C和Pt/C分别为阳极、阴极催化剂制备了膜电极,考察了单电池在常压下的性能,分析了影响电池性能的因素。研究结果显示以氧气为氧化剂在常压、室温工作,50mA/cm~2时,稳定输出电压0.237V;以空气为氧化剂时,在常压、室温工作,输出电流密度40mA/cm~2时稳定的输出比功率为8mW/cm~2。适宜的操作条件:甲醇浓度为2.5mol/L,甲醇流量为1.04mol/L,氧气流量范围60￣100SCCM,空气流量范围为125￣200SCCM。电池性能的初步分析显示,催化层中存在较高的质子传递电阻,使得电池在大电流放电时性能下降较快,限制了比功率的提高。     

Co3O4 nanoparticles decorated Polypyrrole/carbon nanocomposite as efficient bi-functional electrocatalyst for electrochemical water splitting

An effective bi-functional electrocatalyst of Co₃O₄/Polypyrrole/Carbon (Co₃O₄/Ppy/C) nanocomposite was prepared through a simple dry chemical method and used to catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Three types of carbon support as Vulcan carbon, reduced graphite oxide (RGO) and multi-walled carbon nanotubes (MCNTs) were used to study the influence on electrochemical reactions. Spherical shaped Co₃O₄ nanoparticles with 8–10 nm was found uniformly distributed on Ppy/C composite, which were analyzed by X-ray diffraction and transmission electron microscopy techniques. Amongst, Co₃O₄/Ppy/MWCNT shows improved bifunctional electrocatalytic activity towards both OER and HER with relatively low over potential (340 mV vs. 490 mV at 10 mA cm⁻²) and Tafel slope (87 vs. 110 mV dec⁻¹). In addition to that, MWCNT supported Co₃O₄/Ppy nanocomposite exhibits good electronic conductivity and electrochemical stability up to 2000 potential cycles. The results clearly indicate that the Co₃O₄/Ppy/MWCNT nanocomposite could be the promising bi-functional electrocatalyst for efficient water electrolysis.     

N,N-二辛基甘氨酸萃取铑的机理

报道了Ｎ，Ｎ－二辛基甘氨酸从盐酸体系中萃取铑的机理．结果表明：铑的萃取率随酸度、氯离子浓度、铑离子浓度的增大而降低．采用斜率法测得萃合物组成为：Ｒ２ＮＣＨ２ＣＯＯＨＨＲｈ（Ｈ２Ｏ）２Ｃｌ４．萃取反应方程式为：Ｒ２ＮＣＨ２ＣＯＯＨ．ＨＣｌ（Ｏ）＋Ｒｈ（Ｈ２Ｏ）２Ｃｌ－４（Ａ）＝Ｒ２ＮＣＨ２ＣＯＯＨ．ＨＲｈ（Ｈ２Ｏ）２Ｃｌ４（Ｏ）＋Ｃｌ     

高分散度Pt/C电催化剂的制备

Cabot公司Vulcan XC-72型炭黑，经过H2O2氧化处理后作为Pt的载体，H2PtCl6作为金属前驱体制备了高度分散的Pt/C催化剂。讨论了不同条件下H2PtCl6在炭黑上的吸附性能。载体经过H2O2氧化处理24h,H2PtCl6在pH=9下吸收48h，H2 350℃还原2h，可以制备出铂晶粒平均大小为1.8nm的Pt/C电催化剂。     

A nanoporous oxide interlayer makes a better Pt catalyst on a metallic substrate: Nanoflowers on a nanotube bed

To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in electrocatalytic activity （3x） and stability （60x） for methanol oxidation were found, suggesting promising applications in direct methanol fuel cells. The 3x and 60x improvements persist for Pt/Pd catalysts used to overcome the CO poisoning problem.