SusChEM: Spectro-electrochemical and theoretical study of carbon dioxide up-conversion mechanisms using clathrate hydrates

化学部的化学结构、动力学和机制B计划(CSDMB)支持克里斯托夫·罗斯-彼得鲁克教授(PI)和汉尼斯·琼森教授(联合PI)的项目。Rose-Petruck教授和Jónsson教授是布朗大学化学系的教员。该研究项目的重点是将二氧化碳(CO2)电化学转化为有用的化学品。近年来，人们对二氧化碳转化的兴趣显著增加，以应对对非化石燃料产生的可持续产品日益增长的需求。虽然正在做大量工作来推进这些努力，但仍有重大障碍需要克服。其中之一是电化学法产生氢气，这与所需的二氧化碳转化过程不断竞争。这种相互竞争的反应会窃取二氧化碳转化所需的电流(电子流)，这样做会使这一过程效率低下，成本高昂。为了解决这个问题，研究人员正在雪样水晶体中进行二氧化碳的电化学转化，这种晶体被称为笼状水合物，可以储存大量的二氧化碳。这种“雪”与盐和水混合，形成导电的“雪泥”。使用这种混合物进行二氧化碳的电化学转化大大减少了竞争产生的氢气，从而大大提高了产率和反应效率。就二氧化碳转化为增值产品的方式而言，这一发现具有潜在的变革性。以这种方式使用笼状水合物是非常新的，使该方法成功的反应机理尚不清楚。因此，研究人员正在寻求更好地了解这些反应是如何工作的，以及如何操纵它们来优化特定预期产品的产量。研究活动包括与研究仪器公司的合作伙伴关系，这是一家总部位于罗德岛的公司。这家公司是布朗大学向市场转移技术的合作伙伴。通过与领导层联盟的伙伴关系，加强了对历史上代表性不足的团体的招募和指导。将二氧化碳电化学还原为碳质产品是在笼形水合物加载的电解液中进行的。与非笼状电解液相比，这些反应条件大大降低了所需的过电位，并改变了产物光谱。产生了一系列还原电位较低的产品。研究人员推测，当笼状晶体接触工作电极时，笼状水合物结构内的反应是由笼状水分子产生的氢自由基引发的。实验与反应机理和速率的计算相结合。这些计算是基于电子结构的密度泛函理论和最小能量路径计算，以估计各个反应步骤的能垒和基于简谐过渡态理论的速率估计。这项研究调查了包括笼状水合物在内的电解液中的二氧化碳减少机理。这项研究提供了对一类新的反应机理的详细见解，这些反应机理使用笼合物作为水基框架，用于二氧化碳和其他分子的高能效上转换。这些活动包括合作伙伴。研究仪器公司在创业方面贡献力量，并为布朗大学向市场转让技术提供合作伙伴。通过与领导力联盟的伙伴关系，加强了对历来任职人数不足的群体的招聘和辅导。

The Chemical Structure, Dynamics, and Mechanism B Program (CSDMB) of the Chemistry Division supports the project by Professor Christoph Rose-Petruck (PI) and Professor Hannes Jónsson (co-PI). Professors Rose-Petruck and Jónsson are faculty members in the Department of Chemistry at Brown University. The research project focuses on the electrochemical conversion of carbon dioxide (CO2) into useful chemicals. Interest in CO2 conversion has increased significantly in recent years, in response to the increasing demand for sustainable products that are not generated from fossil fuels. While much work is being done to advance these efforts, there are still major hurdles to overcome. One of these is the electro-chemical generation of hydrogen gas that constantly competes with the desired CO2 conversion processes. This competing reaction steals the current (flow of electrons) needed for the CO2 conversion and, in so doing, makes the processes inefficient and costly. To solve this problem, the investigator are conducting the electrochemical conversion of CO2 in snow-like water crystals called clathrate hydrates that can store large amounts of CO2. This "snow" is mixed with salts and water to form an electrically conducting "snow-slush". The use of this mixture for the electro-chemical conversion of CO2 dramatically reduces the competing generation of hydrogen gas, leading to greatly improved yields and reaction efficiency. This discovery has the potential to be transformative in terms of how the conversion of CO2 into value added products is conducted. The use of clathrate hydrates in this fashion is very new, and the reaction mechanisms that enable the success of the approach are unknown. Hence, the researchers are seeking a better understanding of how these reactions work and how they can be manipulated to optimize the yield of a particular desired product. The research activities include a collaborative partnership with the Research Instruments Corporation, a Rhode Island based company. This company is a partner for technology transfer from Brown University into the market place. Recruitment and mentoring of historically underrepresented groups is enhanced through the partnership with the Leadership Alliance.The electrochemical reduction of CO2 into carbonaceous products is carried out in clathrate hydrate-loaded electrolytes. These reaction conditions strongly reduce the needed overpotential and change the product spectrum compared to that obtained with non-clathrate electrolytes. A spectrum of products is produced with low reduction potentials. The researchers hypothesize that reactions inside the clathrate hydrate structures are initiated by hydrogen-radical formation from clathrate water molecules as the clathrate crystals contact the working electrode. The experiments are combined with calculations of the reaction mechanisms and rates. These calculations are based on density functional theory of the electronic structure and minimum energy path calculations to estimate energy barriers for the various reaction steps and rate estimates based on harmonic transition state theory. The research investigates CO2 reduction mechanisms in electrolytes that include clathrate hydrates. The study provides a detailed insight into a new class of reaction mechanisms that use clathrates as water-based frameworks for high energy-efficient up-conversion of CO2 and other molecules. The activities include collaborative partners. The Research Instruments Corporation contributes strength in entrepreneurship and a partner for technology transfer from Brown University into the market place. Recruitment and mentoring of historically underrepresented groups is enhanced through the partnership with the Leadership Alliance.