Devivaraprasad Ruttala, Ramesh Rahul, Naresh Nalajala, Kar Tathagata, Singh Ramesh Kumar, Neergat Manoj
Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB) , Powai, Mumbai, India 400076.
Langmuir. 2014 Jul 29;30(29):8995-9006. doi: 10.1021/la501109g. Epub 2014 Jul 15.
Shape-controlled Pt nanoparticles (cubic, tetrahedral, and cuboctahedral) are synthesized using stabilizers and capping agents. The nanoparticles are cleaned thoroughly and electrochemically characterized in acidic (0.5 M H2SO4 and 0.1 M HClO4) and alkaline (0.1 M NaOH) electrolytes, and their features are compared to that of polycrystalline Pt. Even with less than 100% shape-selectivity and with the truncation at the edges and corners as shown by the ex-situ TEM analysis, the voltammetric features of the shape-controlled nanoparticles correlate very well with that of the respective single-crystal surfaces, particularly the voltammograms of shape-controlled nanoparticles of relatively larger size. Shape-controlled nanoparticles of smaller size show somewhat higher contributions from the other orientations as well because of the unavoidable contribution from the truncation at the edges and corners. The Cu stripping voltammograms qualitatively correlate with the TEM analysis and the voltammograms. The fractions of low-index crystallographic orientations are estimated through the irreversible adsorption of Ge and Bi. Pt-nanocubes with dominant {100} facets are the most active toward oxygen reduction reaction (ORR) in strongly adsorbing H2SO4 electrolytes, while Pt-tetrahedral with dominant {111} facets is the most active in 0.1 M HClO4 and 0.1 M NaOH electrolytes. The difference in ORR activity is attributed to both the structure-sensitivity of the catalyst and the inhibiting effect of the anions present in the electrolytes. Moreover, the percentage of peroxide generation is 1.5-5% in weakly adsorbing (0.1 M HClO4) electrolytes and 5-12% in strongly adsorbing (0.5 M H2SO4 and 0.1 M NaOH) electrolytes.
使用稳定剂和封端剂合成了形状可控的铂纳米颗粒（立方体形、四面体形和立方八面体形）。对这些纳米颗粒进行了彻底清洗，并在酸性（0.5 M硫酸和0.1 M高氯酸）和碱性（0.1 M氢氧化钠）电解质中进行了电化学表征，并将其特性与多晶铂的特性进行了比较。即使形状选择性低于100%，并且如非原位透射电子显微镜分析所示在边缘和角落处存在截断，形状可控纳米颗粒的伏安特性与相应单晶表面的伏安特性仍具有很好的相关性，特别是尺寸相对较大的形状可控纳米颗粒的伏安图。尺寸较小的形状可控纳米颗粒也显示出来自其他取向的贡献略高，这是由于边缘和角落处截断不可避免地产生了贡献。铜溶出伏安图与透射电子显微镜分析和伏安图在定性上相关。通过锗和铋的不可逆吸附估算低指数晶体取向的比例。在强吸附性硫酸电解质中，具有占主导地位的{100}面的铂纳米立方体对氧还原反应（ORR）最具活性，而在0.1 M高氯酸和0.1 M氢氧化钠电解质中，具有占主导地位的{111}面的铂四面体最具活性。ORR活性的差异归因于催化剂的结构敏感性和电解质中存在的阴离子的抑制作用。此外，在弱吸附性（0.1 M高氯酸）电解质中过氧化物生成的百分比为1.5 - 5%，在强吸附性（0.5 M硫酸和0.1 M氢氧化钠）电解质中为5 - 12%。
