EAGER: Continuous, Catalyzed Thermopower Wave Generators Powered by Renewable Biofuels: A New Fuel Cell Concept

便携式储能和输送是现代交通系统的基石，也是便携式电子设备迅速发展的原因，是一个快速发展的领域。此外，最新的自主和移动传感器、机器人和离网无线网络的发展，特别是在微米和纳米尺度上，今天往往因为缺乏类似规模的高功率密度能源系统而受到阻碍。当今的每一种便携式能源技术都有其明显的缺点。电池是最常见的电能存储形式，但与以燃料的化学键存储能量相比，电化学能量密度从根本上说是有限的。此外，电池会随着时间的推移慢慢失去电量，这使得它们不太适合长期储存能量。超级电容器提供了更高的功率密度(重量和体积)，但以能量密度为代价。此外，它们甚至不能像电池一样长时间地保持充电。燃料电池和发动机可以利用化学燃料的高能量密度，但小规模制造较为复杂，因此其功率密度到目前为止一直受到限制。麻省理工学院的Michael Stro教授对一种替代能源设备进行了一些初步研究，这种设备有可能取代这些现有的设备。基于热电波的能源设备可以极大地提高便携式电力设备的能量密度，使其能量密度增加到原来的10倍以上，并具有其他优势，如零存储损失和电荷衰减。高导电性的支架，如碳纳米管(CNT)，沿其长度方向引导热化学反应波；该波还推动载流子产生高功率的电脉冲。根据Stro的说法，这种快速波意味着热电波通常可以在功率密度方面优于使用静态热梯度的传统热电设备，并且在效率方面可能没有相同的限制(通常约为1%-5%)。要测试的概念是，是否可以创造出可以连续发电的热电式燃料电池；以前的设备只能使电脉冲短于一秒。本项目介绍了将金属催化剂纳米颗粒添加到碳纳米管热电管道中的新方面。通过专注于甲酸和甲醇等可生物衍生的燃料，这些发电机可以使用可再生能源。这是一个理想而迫切的项目，因为必须成功地展示几个高风险方面。首先，使用甲酸和甲醇的波传播必须使用低到中等活性的催化材料来进行分解，以沿着热导材料的长度进行分解，包括碳纳米管纤维、无机纳米线或石墨膜。对这些波的理论理解方面的进展将伴随着这一努力。催化剂的选择(S)必须优化活化能；太低，燃料会在不受纳米管控制的情况下自发反应，太高，所需的起爆能太大，降低效率。为了使液体燃料行波管实用化，更常见的金属，如金、铁或铜，必须是活性催化剂金属。除此之外，目标将是制造一种工作装置，并展示更长的使用寿命。这显然是渴望获奖的高风险-高潜在回报项目。为了对这一项目产生更广泛的影响，PI打算利用本科生和研究生研究人员，作为培养工程学多样性的一种手段。PI指出，组成这个项目的实验似乎很适合本科生，他们很快适应并学习如何准备热电波衬底，并学习如何使用仪器。过去，PI与一大批本科生进行了广泛的合作，其中许多人是性别和少数族裔。在一个短而迫切的项目中开发这些方面是困难的，因此PI做出了这一努力是值得赞扬的。

Abstract#1239073Strano, Michael S.Technical BasisPortable energy storage and delivery is the cornerstone of modern transportation systems and the of the proliferation of portable electronic devices and is a rapidly growing field. Additionally, the development of the newest autonomous and mobile sensors, robots, and off-grid wireless networks, particularly at the micro- and nanoscale, is often hampered today by the lack of high power density energy systems of similar size. Each of todays portable energy technologies has its distinct shortcomings. Batteries are the most familiar form of electrical energy storage, but electrochemical energy density is fundamentally limited compared to storing energy in the chemical bonds of fuels. In addition, batteries slowly lose their charge over years, making them less desirable for long-term energy storage. Supercapacitors offer substantially higher power density (in weight and volume terms), but at the expense of energy density. Moreover, they cannot hold their charge even as long as batteries. Fuel cells and engines can use the large energy density of chemical fuels but are more complicated to fabricate at the small scale, so their power density has been limited so far. Professor Michael Strano of the Massachusetts Institute of Technology has performed some initial studies on an alternative energy device that offers the possibility of supplanting these existing devices.Thermopower wave based energy devices may dramatically increase the energy density of portable power devices more than a factor of 10, with other advantages such as zero storage losses and charge decay. High-conductivity scaffolds, like carbon nanotubes (CNTs), direct a hot chemical reaction wave along their length; the wave also pushes charge carriers to create a high-power pulse of electricity. This fast wave means that thermopower waves can often outperform conventional thermoelectrics using static thermal gradients in terms of power density and may not have the same limits on efficiency (usually about 1-5%)according to Strano. The concept to be tested is whether thermopower fuel cells can be created, which could be operated to generate power continuously; previous devices could only make electrical pulses shorter than a second. This project introduces the new aspect of the addition of metal catalyst nanoparticles to the CNT thermoelectric conduits. By focusing on fuels like formic acid and methanol that can be biologically derived, these generators can use renewable energy sources. This is an ideal EAGER project in that several high risk aspects must be successfully demonstrated. First, wave propagation using formic acid and alternatively methanol must be demonstrated using low- to medium-activity catalytic materials for their decomposition along the length of thermal conduit materials, including carbon nanotube fibers, inorganic nanowires, or grapheme films. Advances in theoretical understanding of these waves will accompany this effort. The choice of catalyst(s) must optimize the activation energy; too low and the fuel will react spontaneously without being controlled by the nanotubes, too high and the required initiation energy will be too large, sapping the efficiency. For liquid-fueled-TWGs to be practical, more common metals like Au, Fe, or Cu must be the active catalyst metal. Beyond this, a target would be to fabricate a working device and demonstrate extended operating life. This is clearly the high risk-high potential return project envisioned for EAGER awards. Broader Impacts For this project, the PI intends to utilize undergraduate and graduate researchers, as a means of fostering diversity in Engineering. The PI notes that the experiments that make up this project seem to be well suited for undergraduates, who adapt and learn quickly how to prepare thermopower wave substrates, and learn how to use the instrumentation. The PI has extensively worked with a large body of undergraduate students in the past, many of whom are gender and racial minorities. It is difficult to develop these aspects in a short EAGER project, so the PI is to be commended for making this effort.