Connectivity and ION Conductions in Fuel Cell Membranes Probed by Tunneling Atomic Force Microscopy

在化学系化学测量和成像项目的支持下，以及材料研究部聚合物项目的共同资助下，加州大学圣巴巴拉分校的Steven Buratto教授和他的团队利用导电原子力显微镜（c-AFM）对质子交换膜（PEM）中的离子电导率和孔连通性进行了纳米尺度和单孔通道水平的成像。质子交换膜用于质子交换膜燃料电池。PEM燃料电池使用电化学电池将化学能转化为电能，可以作为高效的电源，提供高功率密度和低环境影响。对燃料电池性能至关重要的是聚合物电解质膜，它是一个有效的质子导体，但也是一个电绝缘体。从质子传导的大小和化学区域的分布来看，对质子传导的详细了解，对于完全理解燃料电池的性能和提高性能的系统方法都是至关重要的。为此，c-AFM将用于关联运行中的半燃料电池的相位和电流图像，并确定电化学活性水表面域的比例。PI和他的团队还将对纳米级结构域的形态和连通性进行成像，作为以下因素的函数：(1)更准确地反映燃料电池运行的环境条件，如高温和低相对湿度；(2)膜的类型和组成；(3)催化剂颗粒与离子通道的接近程度。这些实验的结果将用于获得质子交换膜燃料电池中离子电导率的基本理解，并为下一代膜材料的开发提供灵感和见解。燃料电池的发电效率比内燃机高，而且产生的副产品对环境无害，这使得燃料电池在替代能源和可持续性领域中扮演着重要角色，尤其是当反应物来自可再生资源时。参与该项目的学生将接触到这种替代能源，帮助优化生产聚电解质膜的工业过程，并为新膜材料的发现提供重要的见解。此外，学生将接受最先进的扫描探针显微镜和纳米表征技术的培训。这项拨款支持的研究人员（包括pi）也将积极推广到圣巴巴拉地区的K-12学校。从事该项目的研究人员还计划开发一种可操作的燃料电池的演示，这将包括在UCSB化学系目前正在进行的推广项目中。此外，他们将每年三次访问圣巴巴拉和文图拉县的高中，讨论他们的研究及其影响，并促进科学教育。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, and co-funding from the Polymers Program in the Division of Materials Research, Professor Steven Buratto and his group at University of California-Santa Barbara are utilizing conductive atomic force microscopy (c-AFM) to image ion conductance and pore connectivity in proton exchange membranes (PEM) used in PEM fuel cells on a nanometer length scale and at the level of a single pore channel. PEM fuel cells, which convert chemical energy into electricity using an electrochemical cell, can be used as efficient power sources, offering high power density and low environmental impact. Critical to fuel cell performance is the polymer electrolyte membrane, which is an efficient proton conductor but an electric insulator. A detailed understanding of proton conduction, in terms of the size and distribution of the chemical domains responsible for transport, is crucial to both a complete understanding of fuel cell performance and a systematic approach to improving the performance. To this end, c-AFM will be used to correlate phase and current images taken on an operating half fuel cell and determine the fraction of electrochemically-active aqueous surface domains. The PI and his group will also image the nanoscale domain morphology and connectivity as a function of (1) the environmental conditions that more accurately reflect those of an operating fuel cell such as high temperature and low relative humidity, (2) the membrane type and composition, and (3) the proximity of the catalyst particles to the ion channels. The results of these experiments will be used to gain a fundamental understanding of ion conductance in PEM fuel cells and provide inspiration and insight into the development of the next-generation membranes materials.The possibility of producing power with efficiency greater than internal combustion engines, and with environmentally benign byproducts, makes fuel cells an important player in the field of alternative energy and sustainability, especially if the reactants are derived from renewable resources. Students working on this project will be exposed to this alternative source of power, help optimize industrial processes that produce polyelectrolyte membranes, and provide important insight into the discovery of new membrane materials. In addition, students will be trained in state-of-the-art scanned probe microscopy and nano-characterization techniques. Researchers supported by this grant (including PIs) will also be active in outreach to K-12 schools in the Santa Barbara area. Researchers working on this project also plan to develop a demonstration of an operating fuel cell that will be included in the currently active outreach program in the chemistry department here at UCSB. In addition, they will visit high schools in the Santa Barbara and Ventura Counties three times per year to discuss their research and its impact as well as to promote science education.