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

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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.