Collaborative Research: Design of High Entropy Alloy Electrocatalysts for Mineralization of Total Organic Carbon in Municipal Wastewater

高级氧化工艺(AOPS)，如商品化的UV/AOP工艺，正越来越多地被用作去除美国和世界各地先进水回收和回用工厂中有机微污染物(OMP)的最终处理屏障。在典型的UV/AOP工艺中，UV-C光(波长为200-280 nm)与氧化剂(如过氧化氢)相结合，产生可破坏和矿化OMP(包括个人护理产品、药品、杀虫剂、除草剂等)的OH自由基。目前商业化的UV/AOP需要大量能量来运行，具有高资本支出和运营成本，或者在处理含溴离子的水时产生溴酸盐等有毒产品。电化学高级氧化技术(EAOPs)是一种利用电流在催化电极表面产生羟基自由基来破坏OMPS的技术。与UV/AOPS相比，EAOPS具有效率高、模块化设计、使用清洁可再生能源的电力易于自动化和操作等优点。然而，所需催化电极(电催化剂)的稳定性、寿命和高昂的成本是阻碍EAOPS在水回收和回用厂实施的主要障碍。为了应对这些挑战，该项目的首席研究员(PI)建议利用高熵合金的独特性质(例如，高强度和耐腐蚀性)来设计、合成和优化用于EAOP的新型电催化剂。该项目的成功完成将通过产生基础知识和开发新型电催化剂来提高在水回收和再利用系统中使用EAOPS的效率和成本效益，从而造福社会。还将通过学生教育和培训为社会带来更多好处，包括指导迈阿密大学的两名研究生和佛罗里达国际大学的一名本科生。以富含稀土的金属为前驱体，高熵合金化已成为制备催化活性和耐腐蚀性与贵金属(如铂和Ir)相当的电极的一种有前途的工艺。因此，高熵合金(HEAs)为开发更稳定、更耐用、更具成本效益的电化学高级氧化过程(EAOPs)的催化电极(电催化剂)提供了独特的机会。然而，由于HEA通常是通过混合/合金化五种或五种以上的元素形成的，因此找到产生目标HEA电催化剂的合适的合金成分是具有挑战性的。为了应对这一挑战，该项目的首席研究员(PI)建议将原子建模和模拟与实验相结合，以设计、合成和优化使用富含稀土的金属的新型HEA电催化剂。这项研究的具体目标是：(1)通过原子模拟/模拟和热力学分析筛选出较大的设计空间，设计用于电催化产生水溶液和混合物中的羟基(OH)自由基的富土HEAs；(2)通过制备和小试规模的电化学和湿化学实验，评估和优化电催化剂的结构和性能(活性、耐腐蚀性和耐用性)；以及(3)使用自由基清除/捕获分析和非靶向高分辨率质谱仪，对HEA电催化剂氧化选定的有机微污染物(OMP)进行动力学和机理研究。这项研究的成功完成有可能通过产生组成-结构-性能关系来产生革命性的影响，以指导HEA电化学氧化中水回用和再生的电催化剂的设计和开发。为了实现该项目的教育和培训目标，私人投资机构建议利用迈阿密大学和佛罗里达国际大学的现有项目，从代表性不足的群体中招募和指导本科生参与该项目。此外，PIS计划为市中心和代表性不足的高中生开发和提供STEM浸入式课程，包括在K-12学校和迈阿密的弗罗斯特科学博物馆演讲。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。

Advanced oxidation processes (AOPs) such as the commercial UV/AOP process are increasingly being utilized as a final treatment barrier to remove organic micropollutants (OMPs) in advanced water reclamation and reuse plants in the United States and worldwide. In a typical UV/AOP process, UV-C light (200-280 nm in wavelength) is combined with an oxidant (e.g., hydrogen peroxide) to generate OH free radicals that can destroy and mineralize OMPs including personal care products, pharmaceuticals, pesticides, herbicides, etc. Current commercial UV/AOPs require significant amounts of energy to operate, have high CapEx and OpEx or generate toxic products such as bromate when treating water containing bromide ions. Electrochemical advanced oxidation processes (EAOPs) have emerged as promising technologies that can destroy OMPs using electricity to generate OH radicals at the surface of catalytic electrodes. Compared to UV/AOPs, EAOPs have several advantages including high efficiency, modular design, and ease of automation and operation using electricity from clean renewable energy sources. However, the stability, lifetime, and high cost of the required catalytic electrodes (electrocatalysts) are major impediments to the implementation of EAOPs in water reclamation and reuse plants. To address these challenges, the Principal Investigators (PIs) of this project propose to leverage the unique properties of high entropy alloys (e.g., high strength and corrosion resistance) to design, synthesize, and optimize a new class of electrocatalysts for EAOPs. The successful completion of this project will benefit society through the generation of fundamental knowledge and development of novel electrocatalysts to improve the efficiency and cost effectiveness of using EAOPs in water reclamation and reuse systems. Additional benefits to society will be achieved through student education and training including the mentoring of two graduate students at the University of Miami and one undergraduate student at Florida International University. High entropy alloying has emerged as a promising process for the preparation of electrodes with catalytic activity and corrosion resistance comparable to those of noble metals (e.g., Pt and Ir) using earth-abundant metals as precursors. Thus, high entropy alloys (HEAs) provide unique opportunities to develop more stable, durable, and cost-effective catalytic electrodes (electrocatalysts) for electrochemical advanced oxidation processes (EAOPs). However, it is challenging to find the right alloy composition that produces the target HEA electrocatalyst given that HEAs are typically formed by mixing/alloying five or more elements. To address this challenge, the Principal Investigators (PIs) of this project propose to combine atomistic modeling and simulations with experimentation to design, synthesize, and optimize new HEA electrocatalysts for EAOPs using earth-abundant metals. The specific aims of the research are to (1) design earth-abundant HEAs for the electrocatalytic generation of hydroxyl (OH) radicals in aqueous solutions and mixtures by screening a large design space via atomistic modeling/simulations and thermodynamic analysis; (2) evaluate and optimize electrocatalyst structure and performance (activity, corrosion resistance, and durability) using fabrication and bench scale electrochemical and wet chemical experiments, and (3) conduct kinetic and mechanistic investigations of the oxidation of selected organic micropollutants (OMPs) by HEA electrocatalysts using radical scavenging/trapping assays and non-targeted high-resolution mass spectrometry. The successful completion of this research has the potential for transformative impact through the generation of composition-structure-performance relationships to guide the design and development of HEA electrocatalysts for water reuse and reclamation using electrochemical oxidation. To implement the education and training goals of the project, the PIs propose to leverage existing programs at the University of Miami and Florida International University to recruit and mentor undergraduate students from underrepresented groups to work on the project. In addition, the PIs plan to develop and deliver STEM immersion programs to inner-city and underrepresented high school students including presentations at K-12 schools and the Frost Museum of Science in Miami.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.