CAREER: Electronic transport and interfacial effects on electrochemical hydrogen evolution reaction for transition metal dichalcogenides

电化学催化可用于从水中产生氢气，从而为从天然气或石油中产生氢气的传统工艺提供了一种可持续的替代方案。近年来，一类被称为过渡金属二硫族化合物（TMDCs）的低成本化学材料已被确定为有前途的材料，用于水基制氢，为燃料电池提供动力，并作为制造化学品的原材料。尽管前景光明，但还需要更多的科学理解和工程设计来最大限度地提高二硫化物材料的性能，使其达到与更昂贵的最先进的铂基催化剂相媲美的水平。为此，该项目将探索二硫化物材料的基本方面及其利用独特的反应堆系统产氢的有效性。这项研究将有助于为可持续能源和化学品的未来铺平道路，同时也为美国在燃料和化学品制造领域的长期竞争力奠定基础。这项研究将与强调代表性不足群体参与的教育和外联活动结合起来。该项目在一定程度上寻求答案，即电子输运性质和界面效应（而不是氢吸附的自由能）限制了TMDCs上析氢反应（HER）的总体速率。单晶片状纳米器件将被用作HER微反应器，它可以精确控制催化位点的密度和类型，并精确测量催化剂内的电荷传输，以及催化剂/集流器界面上的肖特基势垒。研究了TMDC的电学性能、界面肖特基势垒和氢吸附自由能随TMDCs从半导体2H相到半金属1T′相转变的变化规律，TMDCs的应变工程，以及TMDCs的不同集流器。在硫酸电解质溶液中，使用标准的三电极电池与单个TMDC纳米器件耦合，各种性能的变化将与测量的HER活性相关。半导体的MoS2和WS2，半金属的MoTe2和WTe2纳米片将用于拟议的研究，通过化学气相沉积生长或从化学气相传输生长的大块晶体中机械剥离。除了优化用于HER的TMDC材料外，纳米器件平台还可以应用于其他电和光催化剂，以将其催化性能与催化位点的能量学、平衡电学性能、界面效应和光子诱导的激发态等关键参数相关联。该项目将通过三个推广项目将研究与教育和推广活动联系起来，分别针对普通公众（耶鲁大学西校区的周末能源研讨会）、代表性不足的本科生（少数族裔教员每月举办的系列研讨会）和当地高中生（基于TMDC薄膜的HER工具包和工作手册）。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Electrochemical catalysis can be used to generate hydrogen from water, thereby offering a sustainable alternative to conventional processes that generate hydrogen from natural gas or petroleum. In recent years, a class of low-cost chemical materials, known as transition metal dichalcogenides (TMDCs), have been identified as promising materials for water-based hydrogen production to power fuel cells and as a raw material for the manufacture of chemicals. Despite their promise, additional scientific understanding and engineering design will be needed to maximize the performance of the dichalcogenide materials to levels rivaling more expensive state-of-the-art platinum-based catalysts. To that end, the project will explore fundamental aspects of the dichalcogenide materials and their effectiveness for hydrogen generation utilizing a unique reactor system. The research will help pave the path to a sustainable energy and chemicals future while also laying ground work for long-term competitiveness of the U.S. in the fuels and chemical manufacturing sectors. The research will be integrated with educational and outreach activities emphasizing participation by under-represented groups. The project seeks answers to the extent that electronic transport properties and interfacial effects (rather than the free energy of hydrogen adsorption) limit the overall rate of the hydrogen evolution reaction (HER) on TMDCs. A single-crystalline flake nanodevice will be employed as a HER micro-reactor, which allows precise control of the density and types of catalytic sites, and accurate measurements of charge transport within the catalyst, as well as the Schottky barrier at the catalyst/current collector interface. Three aims are proposed to study how the TMDC electrical properties, interfacial Schottky barrier, and the hydrogen adsorption free energy change as a function of 1) the phase transition from the semiconducting 2H to the semi-metallic 1T' phase of TMDCs, 2) strain engineering of TMDCs, and 3) different current collectors. The changes in the various properties will be correlated with the measured HER activities using a standard three-electrode cell coupled to the individual TMDC nanodevices in sulfuric acid electrolyte solution. Semiconducting MoS2 and WS2, and semi-metallic MoTe2 and WTe2 nanoflakes will be used for the proposed research, grown by chemical vapor deposition or exfoliated mechanically from bulk crystals grown by chemical vapor transport. Beyond optimization of TMDC materials for HER, the nanodevice platform can be applied to other electro- and photo-catalysts to correlate their catalytic properties to critical parameters such as energetics of catalytic sites, equilibrium electrical properties, interfacial effects, and excited states induced by photons. The project will link the research to education and outreach activities via three outreach programs targeting, respectively, the general public (a weekend Energy symposium at Yale West Campus), under-represented undergraduate students (a monthly seminar series given by minority faculty members), and local high school students (a demonstration HER kit and workbook based on TMDC thin films).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.