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

高级氧化工艺（AOPs），如商业UV/AOP工艺，越来越多地被用作去除有机微污染物（OMPs）的最终处理屏障，在美国和世界各地的高级水回收和再利用工厂。在典型的UV/AOP工艺中，UV- c光（波长200- 280nm）与氧化剂（如过氧化氢）结合产生OH自由基，OH自由基可以破坏和矿化omp，包括个人护理产品、药品、杀虫剂、除草剂等。目前的商用UV/AOPs需要大量的能源来运行，具有很高的资本支出和运营成本，或者在处理含有溴化物离子的水时产生溴酸盐等有毒产物。电化学高级氧化工艺（EAOPs）是一种很有前途的技术，它可以利用电在催化电极表面产生OH自由基来破坏omp。与UV/AOPs相比，EAOPs具有几个优势，包括高效率、模块化设计、易于自动化和使用清洁可再生能源的电力。然而，所需的催化电极（电催化剂）的稳定性、寿命和高成本是在水回收和再利用工厂实施EAOPs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能（例如，高强度和耐腐蚀性）来设计、合成和优化一类新的EAOPs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。通过学生教育和培训，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，将为社会带来额外的好处。高熵合金化已经成为一种很有前途的方法，可以使用地球上丰富的金属作为前体，制备具有与贵金属（例如Pt和Ir）相当的催化活性和耐腐蚀性的电极。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）催化电极（电催化剂）提供了独特的机会。然而，由于HEA通常是由五种或五种以上元素混合/合金化而形成的，因此找到合适的合金成分来生产目标HEA电催化剂是具有挑战性的。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，设计、合成和优化使用地球上丰富金属的EAOPs的新型HEA电催化剂。该研究的具体目标是：(1)通过原子建模/模拟和热力学分析筛选大的设计空间，设计出地球丰富的HEAs，用于在水溶液和混合物中电催化生成羟基（OH）自由基；(2)利用制造和实验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、耐腐蚀性和耐久性）；(3)利用自由基清除/捕获法和非靶向高分辨率质谱法对HEA电催化剂氧化选定的有机微污染物（OMPs）进行动力学和机理研究。这项研究的成功完成有可能产生变革性的影响，通过生成成分-结构-性能关系来指导设计和开发用于水再利用和利用电化学氧化回收的HEA电催化剂。为了实现项目的教育和培训目标，项目负责人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项目。此外，pi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进行演讲。该奖项反映了美国国家科学基金会的法定使命，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。

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.