Collaborative Research: EAGER: Insights into the Hydrogen Evolution Reaction of Transition Metal Dichalcogenide Nanocrystals by In-situ Electron Paramagnetic Resonance Spectroscopy

氢(H2)作为清洁能源燃料和化学前体的大规模部署将需要取代昂贵的铂族金属，这些金属通过利用可再生电力的氢析出反应(HER)催化水的电化学分解。先前的研究已经确定了一类富含稀土的过渡金属二卤化物(TMD)纳米晶(NC)电催化材料，它们在HER中显示出巨大的应用前景。该项目将通过采用现场分析技术和理论计算相结合的方式，进一步推动TMD-NC技术的进步，这些计算将提供对TMD NCS中活性催化位置的精确知识和理解。结合对氢能的相应机理理解，该项目将为发现和设计更高效、更低成本的氢能催化剂铺平道路，从而实现氢经济。更广泛地说，该项目包括支持可再生能源可持续技术和先进催化剂的教育、推广和劳动力培训举措。这个合作的早期概念探索研究助学金(AGER)项目的总体目标是实时建立原子尺度的整体理解，了解2H-MoS2 NC催化剂上HER的结构、化学、催化活性和机理之间的相互作用。该团队将利用原位电子顺磁共振(EPR)光谱和原位X射线探头与密度泛函理论(DFT)计算相结合的方法来实现这一点。EPR光谱将在广泛的操作条件下灵敏地探测顺磁催化中心的局部环境，以及它们在催化氧化还原过程中的行为。作为对原位EPR谱的补充，原位X射线技术将被用来探测非磁性(即非EPR活性物种和其他非自旋相关因素)催化活性HER物种，并将使顺磁/自旋效应从整体催化活性中分离出来。EPR光谱特性的变化，如信号形状、宽度、强度和g因子(塞曼分裂)，作为潜在偏置、时间和温度的函数，将与测量的HER活动相关联，以实现该提案的中心目标。密度泛函计算将清楚地识别HER活性缺陷中心的磁性状态，将这些磁性状态与缺陷的局部环境相关联，并计算相应的EPR谱，考虑到吸附、电极极化和溶剂筛选的作用。这项研究的结果将解决在理解TMD催化活性方面的关键挑战，并为合理设计基于TMD的电催化剂提供基本的见解。除了对TMD电催化的直接关注外，该项目还将推动原位EPR作为催化科学的一种有前途的工具。从更广泛的影响角度来看，该项目将对德克萨斯大学埃尔帕索分校的拉美裔学生(82%)进行可再生能源研究方面的培训。与项目有关的教育材料将与若干外联活动结合起来，旨在扩大埃尔帕索地区布利斯堡的军人和退伍军人对科学研究的参与。关于催化及其在可再生能源中的作用的教育模块将在马萨诸塞大学阿默斯特分校开发和提供，作为K-12 STEM教育者年度专业发展研讨会的一部分。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The large-scale deployment of hydrogen (H2) as a clean-energy fuel and chemical precursor will require replacing expensive platinum-group metals that catalyze the electrochemical splitting of water via the hydrogen evolution reaction (HER) utilizing renewable electricity. Previous research has identified a class of earth-abundant transition-metal dichalcogenide (TMD) nanocrystalline (NC) electrocatalytic materials that show great promise for the HER. The project will enable further advances in TMD-NC technology by employing a combination of in-situ analytical techniques coupled with theoretical calculations that will provide precise knowledge and understanding of the active catalytic sites in TMD NCs. Together with corresponding mechanistic understanding of the HER, the project will pave the way for the discovery and design of more efficient and less costly HER catalysts, thereby enabling the hydrogen economy. More broadly, the project includes educational, outreach, and workforce training initiatives supporting sustainable technologies for renewable energy and advanced catalysts. The overarching goal of this collaborative Early-concept Grants for Exploratory Research (EAGER) project is to establish an atomic-scale holistic understanding of the interplay between the structure, chemistry, catalytic activity, and mechanisms of the HER on 2H-MoS2 NC catalysts in real time. The team will accomplish this by employing a combination of in-situ electron paramagnetic resonance (EPR) spectroscopy and in-situ x-ray probes coupled with density functional theory (DFT) calculations. EPR spectroscopy will sensitively probe the local environment of paramagnetic catalytic sites, as well as their behavior in catalytic redox processes, under a wide range of operating conditions. In-situ x-ray techniques, complementary to in-situ EPR spectroscopy, will be employed to probe for the non-magnetic (i.e., non-EPR active species and other non-spin related factors) catalytically active HER species, and will enable the separation of the paramagnetic/spin effect from the overall catalytic activity. The changes in the EPR spectral properties, such as signal shape, width, intensity, and g-factor (Zeeman splitting) as a function of potential bias, time, and temperature, will be correlated with the measured HER activities to achieve the central goals of the proposal. DFT calculations will clearly identify the magnetic states of HER-active defect centers, correlate these magnetic states with the local environment of the defect, and calculate corresponding EPR spectra, taking into account the role of adsorbates, electrode polarization, and solvent screening. The outcomes of this research will resolve key challenges in understanding the catalytic activity of TMDs and provide fundamental insights that enable rational design of TMD-based electrocatalysts. Beyond the immediate focus on TMD electrocatalysis, the project will advance in-situ EPR as a promising tool for catalysis science. From the broader impacts perspective, the project will train the Hispanic student population (82%) at the University of Texas at El Paso in renewable energy research. Project-related educational material will be integrated with several outreach activities geared towards broadening participation of army personal and veterans at Fort Bliss in the El Paso region in scientific research. Educational modules on catalysis and its role in renewable energy will be developed and delivered at the University of Massachusetts, Amherst as part of the annual professional development workshops for K-12 STEM educators.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.