请求电化学分析大神帮我看看ORR在酸性条件下测出的结果对不对。?最近在做ORR,碱性条件下导师以前做过,还可以参考,可是酸性条件下测出的结果总感觉不对,这是我在酸性条件下测出的样品和Pt/C的对比LSV图(1600rpm), 测试 条件是: 参比电极 AgCl,电压扫的范围是-0.2-0.8,介质是0.5M H2SO4. 感到最大的不对就是我测的PtC电极(PtC的lsv曲线也是我测的),大家看看有没有什么问题,因为我扫描范围是从-0.2-0.8.而我看有些文献是从0.012V-1.012V,例如这篇JACS:Bamboo-like Carbon Nanotube/Fe3C Nanoparticle Hybrids and Their Highly Efficient Catalysis for Oxygen Reduction,这样换算出的PtC电极在酸性条件下的RHE onset电位是在0.95eV(其中Pt丝它是AgCl电极在HClO4做的,而碳材料是AgCl电极在0.5MH2SO4做的); 可是另外一篇JACS(也是我参考它扫描的)Highly Efficient Metal-Free Growth of Nitrogen-Doped Single-Walled Carbon Nanotubes on Plasma-Etched Substrates for Oxygen Reduction扫描范围却是从-0.2-0.8(AgCl,0.5MH2SO4),而且onset值差不多也是在这附近。所以我有点懵了,还有文献说potential貌似越负越好,请看这句话(Journal of Power Sources 264 (2014) 114e122??Meanwhile, its Eonset (0.725 V vs. RHE) and E1/2 (0.623 V vs. RHE) are more negative than those of Pt/OMC (0.828and 0.733 V vs. RHE).),但大多文献都是说越正越接近Pt/C越好,这个也请大神回答下。唉,感觉ORR酸性测好像没有一个标准,基本的电极换算我也列出来了,E(RHE)=E(Hg/HgO)+0.0591*pH+0.098 RHE=Ag/AgCl+0.059PH+0.197 0.5molH2SO4 ph=0 0.1M KOH, PH=13, E(RHE)=E(Hg/HgO)+0.8633 E(SHE)= E(Hg/HgO) +0.098 求ORR大神给我指点下迷津,小弟已经通读了chemsocrev最新出的orr综述以及2015angew那篇关于orr的综述,还是不能解惑,所以不要泛泛叫我看了,请给我实质性帮助,第一,我的测试结果有没有问题;第二酸性条件下参考RHE,potential越负点好还是正点好? 酸性对比.jpg查看更多7个回答 . 13人已关注
求大神:反相微乳液法合成Pt@SiO2无法完成包覆的问题?采用油胺油酸 十八烯 还原Pt(acac)2来制备出约2nm pt纳米粒子,分散度也较好(下图1),但是在得到粒子进行Igepal-环己烷-氨水-TEOS包覆的时候,出现较大的问题无法进行正常包覆? ???包覆比例开始参照文献Langmuir 2010, 26(21), 16469–16473? ???Cyclohexane(25 mL) was mixed with igepal CO-630 (8.0 mL) and NH4OH solution (1.0 mL), and the mixture was stirred for 10 min. A NiPt particle dispersion in cyclohexane (25 mL, 10 mM with respect to the precursor concentration) was added into the mixture. After 30 s, TMOS (1.0 mL) was injected, and the resulting mixture was stirred for 60 min at room temperature. The NiPt@SiO2 particles were precipitated by adding methanol (10 mL) and were purified by a repetitive dispersion/precipitation cycle in ethanol.其中TMOS改为了TEOS,考虑到TEOS水解较慢,这里把反应时间增大到12h,最终得到的结果如下图2所示,粒子根本无法进行包覆,粒子仍然聚在一个区域。? ???考虑到是否粒子过小而造成这种现象,仅采用油胺还原 乙酰丙酮铂 得到大小约7nm纳米粒子,分散度比之前2nm的更好,之前在盖德查到有人说TEOS滴加过快也会造成无法包覆,所以这次试验TEOS一分钟加一次,每次加25微升。滴加完毕后搅拌48h后加入甲醇,出现明显的分层,但是下层只有极少数的黑色沉淀,照电镜后发现也没有包覆成功,水解的 二氧化硅 球倒是特别均匀,如图3所示。? ???后来考虑到是不是这个微乳液的配比不太符合,有参考了文献 J. Phys. Chem. C 2010, 114, 2512–2518 ? ? In a 250 mL Erlenmeyer flask, 3 mL of Igepal CO-520 was added to 100 mL of cyclohexane, and the mixture wasstirred at room temperature for 5 min. Nine milligrams of Fe-Pt nanocrystals redispersed in 9 mL of cyclohexane was added to the stirring Igepal solution. After stirring for 5 min, 0.65 mL of 30% aqueous NH4OH solution was added dropwise to the mixture, followed by immediate addition of TEOS; 0.375-1.0 mL of TEOS was added, depending on the desired silica shell thickness, which could be increased from 3 to 13 nm by increasing the amount of TEOS. The mixture was stirred for 48 h, and then the SiO2-coated Fe-Pt nanocrystals were extracted from the cyclohexane phase by adding 50 mL of methanol. The cyclohexane phase was discarded. The nanoparticle dispersion was collected in a 100 mL, round-bottom flask and placed on a rotary evaporator to concentrate the dispersion down to a volume of 10 mL. 采用之前制备的粒子烘干后取9mg参照这种方法进行包覆,TEOS滴加量为0.5ml,反应48h后加入甲醇分层后,甲醇相内并没有出现沉淀,也就是说根本没有包覆成功的粒子出现,不知道实验过程中出现了什么问题,请教一下各位做这个方面的同学怎么解决这种现象。图1.png图2.png图3.png查看更多7个回答 . 25人已关注