Mechanisms of the electrochemical oxidation, restructuring, and dissolution of platinum

铂的电化学氧化、重组和溶解机制

• 批准号: 418603497
• 负责人: Dr. Serhiy Cherevko
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418603497?language=en
• 关键词: Mechanisms; electrochemical; oxidation; restructuring; dissolution

The electrochemical oxidation of platinum and the reduction of the formed ultrathin oxide films result in Pt dissolution and surface restructuring, which is a main origin of Pt catalyst degradation in fuel cells. Although Pt oxidation has been studied for a long time, a more detailed understanding of their atomic-scale mechanisms has up to now been obtained only for the close-packed Pt(111) surface. For the accompanying Pt dissolution, microscopic models are even lacking completely. In this project we will systematically study the oxidation, oxide reduction, and dissolution of Pt single crystal electrodes, focusing on the more open Pt(001), Pt(110), and Pt(310) surfaces. In situ surface X-ray scattering techniques will be employed for clarifying the precise atomic and nanoscale surface structure, electrochemical mass spectrometry for determining the potential- and time-dependent rates of anodic and cathodic dissolution. We will specifically investigate (i) the mechanisms, kinetics, and reversibility of the place exchange between oxygen and Pt surface atoms in the initial stages of oxidation, (ii) the structure and structural evolution of the formed Pt oxide film, (iii) the surface restructuring caused by oxidation/reduction cycles, and (iv) how all of this influences Pt dissolution. The mass spectrometry measurements will cover a wide range of oxidation parameters, including the potential-time program, solution composition (anion species, pH, O2 content), and temperature, allowing to identify cases that are of particular fundamental interest or practical relevance for catalyst stability. With X-ray scattering we will obtain detailed structural data for a more restricted range of oxidation conditions, whose selection will be guided by the dissolution data. Together with density functional theory calculations by collaborating groups, these results should provide detailed insights on the microscopic atomic-scale mechanism. As a first test whether the developed models can be applied for understanding the stability of real catalysts, we will additionally perform complementary studies for an intermediate model system – shape-controlled Pt nanocrystals with defined facets on planar carbon supports.

铂的电化学氧化和所形成的氧化物膜的还原导致铂溶解和表面重构，这是燃料电池中铂催化剂劣化的主要原因。虽然Pt的氧化已经研究了很长时间，但迄今为止，仅对紧密堆积的Pt（111）表面获得了对其原子尺度机制的更详细的理解。对于伴随的铂溶解，微观模型甚至完全缺乏。 在这个项目中，我们将系统地研究Pt单晶电极的氧化，氧化物还原和溶解，重点是更开放的Pt（001），Pt（110）和Pt（310）表面。原位表面X射线散射技术将用于澄清精确的原子和纳米级表面结构，电化学质谱法用于确定阳极和阴极溶解的电位和时间依赖性速率。我们将具体调查（i）的机制，动力学和可逆性的氧和Pt表面原子之间的位置交换在氧化的初始阶段，（ii）形成的Pt氧化膜的结构和结构演变，（iii）由氧化/还原循环引起的表面重组，以及（iv）如何所有这些影响Pt溶解。质谱测量将涵盖广泛的氧化参数，包括电位-时间程序、溶液组成（阴离子物质、pH值、O2含量）和温度，从而能够识别对催化剂稳定性具有特别重要意义或实际相关性的情况。与X射线散射，我们将获得详细的结构数据的氧化条件，其选择将指导溶解数据的范围更有限。再加上合作小组的密度泛函理论计算，这些结果应该提供微观原子尺度机制的详细见解。作为第一个测试是否开发的模型可以应用于了解真实的催化剂的稳定性，我们将另外进行补充研究的中间模型系统-形状控制的Pt纳米晶体与平面碳载体上的定义方面。