Mechanistic Understanding of Electrocatalytic Bio-oil Hydrogenation Rates: Towards a Cost-effective Electrochemical System

美国经济中的运输部门产生了很大一部分温室气体排放。增加可再生燃料的使用是减少与运输相关的温室气体排放以及确保国内可持续燃料资源的一种选择。帮助满足运输需求的一个有希望的战略是利用可再生电力从生物质废物中合成运输级燃料(例如液体碳氢化合物)，从而实现二氧化碳中性燃料来源。生物油加氢被认为是生产生物燃料最耗资和最耗能的步骤。解决这一挑战的一个有希望的方法是使用生物质的电催化加氢(ECH)，因为它提供了一种可持续的燃料生产方法，并能够使用可再生电力。然而，需要改进的电化学系统和电催化剂才能使ECH在经济上具有竞争力。这个基础研究项目将解决能源效率、产品产量挑战和ECH的经济分析。该项目将重点研究水相金属加氢反应的分子途径和反应瓶颈。该研究项目将为密歇根大学的两名博士生提供多学科培训，使他们能够在材料合成和表征、计算建模和电催化方面进行尖端研究。代表不足的少数族裔和女性学生将在高中和本科两级从事研究和推广活动。这项基础性研究项目将集中在假设指导下研究铂族金属和双金属合金在水相中的电化学氢化反应。这项研究将促进金属和双金属合金在利用可再生电力进行可持续燃料生产的生物质废物选择性加氢方面的知识。该项目的目标是通过关注三个主要领域，有机物和氢在金属表面的吸附，金属和双金属的电催化氢化速率，以及使用理论和实验相结合的方法来了解吸附和反应速率之间的联系，以及预测更活跃和选择性的合金，来帮助产生电催化氢化的广泛应用。该团队将在受控条件下测量和计算不同金属上的本征反应速率，然后找到与吸附能和反应中间体之间的关联。S项目的指导假设是，通过从具有中等加氢活性的金属开始，并进行修饰以生成双金属(例如铂合金)，可以调整氧化的芳香族和氢的吸附能量，以提高反应速度和能源效率。为了探测反应途径和中间体，该项目将测量吸附等温线，并在反应条件下使用表面增强拉曼光谱选择性地探测电催化剂表面附近的物种。作为对实验工作的补充，该项目包括氢和含氧芳烃吸附能的密度泛函理论模拟以及在水中的外加电位下的ECH活性。这一奖项反映了NSF的法定使命，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 transportation sector of the U.S. economy generates a large portion of greenhouse gas emissions. Increased use of renewable fuels is one option to reduce transportation-related greenhouse gas emissions and also to secure domestic, sustainable resources for fuel. One promising strategy to help meet transport needs is to synthesize transportation-grade fuels (e.g. liquid hydrocarbons) from biomass waste using renewable electricity, thereby enabling a CO2-neutral fuel source. Bio-oil hydrogenation is known to be the most capital- and energy-intensive steps for biofuel production. One promising approach to address this challenge is to use electrocatalytic hydrogenation (ECH) of biomass because it provides a sustainable method of fuel production and enables the use of renewable electricity. However, improved electrochemical systems and electrocatalysts are needed to make ECH economically competitive. This fundamental research project will address energy efficiency, product yield challenges, and economic analysis of ECH. The project will focus on the molecular pathways and reaction bottlenecks for hydrogenation reactions on metals in the aqueous phase. The research project will provide multidisciplinary training to two PhD students at the University of Michigan and enable them to conduct cutting-edge research in materials synthesis and characterization, computational modeling, and electrocatalysis. Underrepresented minority and female students will be engaged in research and outreach at both the high school and undergraduate level. This fundamental research project will focus on the hypothesis-directed study of electrochemical hydrogenation reactions on platinum group metals and bimetallic alloys in aqueous phase. The research will advance knowledge of metals and bimetallic alloys for use in selective hydrogenation of biomass waste using renewable electricity for sustainable fuel production. The project's goal is to help engender the widespread use of electrocatalytic hydrogenation by focusing on three main areas, the adsorption of organics and hydrogen on metal surfaces, electrocatalytic hydrogenation rates on metals and bimetallics, and using a combination of theory and experiment to understand the link between adsorption and reaction rates and selectivity to predict more active and selective alloys. The team will measure and compute intrinsic reaction rates under controlled conditions on different metals, and then find correlations with adsorption energies and reaction intermediates. The project?s guiding hypothesis is that by starting with metals having moderate activity for hydrogenation and modifying to create bimetallics (e.g., Pt-alloys), one can tune the oxygenated aromatic and hydrogen adsorption energies to increase reaction rates and energy efficiency. To probe the reaction pathway and intermediates, the project will measure adsorption isotherms and use surface-enhanced Raman spectroscopy under reaction conditions to selectively probe species near the electrocatalyst surface. To complement the experimental work, the project includes density functional theory modeling of hydrogen and oxygenated aromatic adsorption energies and ECH activity at applied potentials in water. Fundamental knowledge will result of molecular-level reaction mechanisms for electrocatalytic hydrogenation systems.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.