EAGER: Unravelling the Origin of Electrocatalytic Activity of Metal Free Conjugated Polymers: Designing Carbon-Based Electrocatalysts

该项目探讨了基于氧相关反应，特别是氢燃料电池所必需的氧还原反应（ORR），为可持续能源设计电催化剂的潜力。虽然铂基阴极催化剂仍然是氢燃料电池应用中最有效的催化剂，但在设计和开发低成本过渡金属替代品以及各种碳基催化剂（如碳纳米管）方面取得了相当大的进展。这个早期概念探索性研究资助（EAGER）项目通过共轭聚合物（CP）的设计，合成和性能评估扩展了碳基ORR催化剂的能力。目前，氯化石蜡的性能受到合成电活性氯化石蜡的挑战以及与将技术提升到与铂相媲美的水平所需的结构-功能特性相关的知识差距的限制。 因此，该项目的重点是将合成参数与材料性质（即有序和结构）联系起来，同时调制所得CP的电荷和自旋分布。将追求两个具体目标- 1）从杂环单体合成电活性聚合物，和2）建立结构与功能的关系。 实验结构-功能关系，从而获得将提供有价值的数据，需要为未来的理论/计算工作，以指导知识驱动的优化非金属碳基聚合物氧还原电催化剂，以及其他潜在的应用这一类的电化学materials.The项目是基于中心假设，即CP的电催化活性与这些材料中的电荷存储。 研究者和其他人先前的研究将CP中的电荷转移与它们的极化状态联系起来。在该系统中，掺杂剂通过使π电子沿着大分子链离域来限定分子内共轭长度的延伸，从而促进CP的禁带中局部电子能级的出现。 虽然CP因其在太阳能电池中的性能而广为人知，并且作为电催化剂和电催化剂的前体也显示出有前途的性质，但由于两个主要问题，它们的利用受到阻碍：a）它们的低溶解度，限制了它们的合成，以及B）与性能与荷电状态相关的知识空白。EAGER项目将利用研究者实验室开发的干聚合技术合成具有一系列结构和化学特性的各种氯化石蜡。CP通过氧化化学气相沉积（oCVD）一步合成和掺杂。掺杂剂浓度将通过控制oCVD工艺中的气相组成来调节。将在ORR中评估合成材料的电催化性能，从而创建一个超越当前最先进水平的连接结构与性能关系的平台。该项目有可能在CP中建立化学结构与电活性之间的关系，从而为提高碳基电催化剂的性能和耐久性提供基础。该项目还提供了一条将材料选择和合成方法扩展到其他碳基材料（如共轭微孔聚合物和网络）的途径。该奖项反映了NSF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。

The project explores the potential of designing electrocatalysts for sustainable energy based on oxygen-related reactions, especially the oxygen reduction reaction (ORR) essential to hydrogen fuel cells. While platinum-based cathode catalysts remain the most effective catalysts for hydrogen fuel cell applications, considerable progress has been made in the design and development of lower-cost transition metal alternatives, as well as a variety of carbon-based catalysts (such as carbon nanotubes). This Early-concept Grant for Exploratory Research (EAGER) project extends the capabilities of carbon-based ORR catalysts through the design, synthesis, and performance evaluation of conjugated polymers (CPs). The performance of CPs is currently limited by challenges in synthesizing electroactive CPs, as well as by knowledge gaps related to structure-function properties required to advance the technology to levels rivaling platinum. Thus, the project focuses on connecting synthetic parameters with materials properties (i.e. order and structure), while modulating the charge and spin distributions of the resulting CPs. Two specific aims will be pursued – 1) Synthesize electroactive polymers from heterocyclic monomers, and 2) Establish structure-to-function relationships. The experimental structure-function relationships thus obtained will provide valuable data needed for future theoretical/computational efforts to guide knowledge-driven optimization of non-metal carbon-based polymeric oxygen reduction electrocatalysts, as well as other potential applications of this class of electrochemical materials.The project is based on the central hypothesis that the electrocatalytic activity of CPs is related to the charge storage in these materials. Prior studies by the investigator and others have related the charge transfer in CPs to their polaronic states. In this system, the dopants define the extension of intramolecular conjugation lengths by delocalizing pi electrons along the chain of macromolecules, thereby facilitating the emergence of localized electronic levels in the forbidden bandgap of the CPs. While CPs are widely known for their performance in solar cells, and have also shown promising properties both as electroatalysts and precursors to electrocatalysts, their utilization has been hampered due to two main issues: a) their low solubilities, limiting their synthesis, and b) knowledge gaps related to the correlation of performance with the state-of-charge. The EAGER project will utilize a dry polymerization technique developed in the investigator’s laboratory to synthesize various CPs having a range of structural and chemical properties. The CPs are being synthesized and doped in one step via oxidative chemical vapor deposition (oCVD). The dopant concentration will be adjusted by controlling vapor phase composition in the oCVD process. The synthesized materials will be evaluated for their electrocatalytic properties in the ORR, thereby creating a platform for linking structure-to-properties relationships beyond the current state of the art. The project has the potential to establish a relationship between chemical structure and electroactivity in CPs, thus providing a basis for enhancing the performance and durability of carbon-based electrocatalysts. The project also provides a path for expansion of the materials selection and synthesis methods into other carbon-based materials such as conjugated microporous polymers and networks.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.