Electrochemistry ARL-BAA-0025: Megalibraries of Electrocatalysts - Synthesis and Optical Screening Methods
Abstract
Electrocatalytic materials are important for many DoD relevant devices and processes, including fuel cells, off-site fuel production, and battery technologies, among others. However, current electrocatalyst materials suffer from high cost, low efficiency, poor selectivity, and stability issues. Therefore, there is a pressing need for discovering new enabling electrocatalytic materials, which demands a robust, efficient, and high-throughput approach. In this proposal, the development of critical new synthesis and analytical tools that are poised to rapidly accelerate electrocatalyst discovery and optimization will be explored. As proof-of-concept, the platform will focus on the electrocatalytic oxygen reduction reaction (ORR), a lynchpin in the global electrocatalysis effort - for efficient fuel cells and H2O2 production. This work aims to develop an unprecedentedly high-throughput electrocatalyst synthesis and screening platform to accelerate the discovery of improved electrocatalysts for ORR. First, polymer pen lithography, an emerging technology developed with DoD funding, will be used to create chip-based arrays consisting of millions of possible material candidates in the form of nanoparticle "megalibraries". A megalibrary is a single 2 cm x 2 cm chip that can contain millions of unique and well-defined nanoparticles. Megalibraries are synthesized through parallelized scanning probe block copolymer lithography, wherein defined concentrations of nanoparticle precursors are site-specifically deposited, and subsequently transformed into nanoparticles. In just one experiment >1,000,000 unique nanomaterials, whose composition and size are controlled and spatially encoded on a chip, can be synthesized. The nanomaterials of interest will be comprised of Au, Ag, Cu, Co, Ni, Pd, Pt, Sn, and Fe, and combinations thereof, with emphasis on new Fe, Pt, and Cu-based nanoparticles. This nine-element palette will lead to millions of new materials that have never existed before. Importantly, these constituent elements 1) span a range of precious metals as well as earth-abundant transition metals, 2) have individually or in certain combinations been shown as promising materials for ORR, and 3) are compatible with the megalibrary synthesis strategy. To identify promising candidates from the megalibraries, complementary screening methods that distinguish high performers from others must be developed. An optical method will be used to spatially resolve catalyst performance at a speed and scale that matches the synthetic throughput described above. Probes that react with H2O2 for ORR can be incorporated into reaction matrices coating megalibraries to trap products as they are made and reveal an intense fluorescence signal. Spatially resolved fluorescence turn-on can be used as an indicator for catalyst activity and selectivity, indicating the performance of each material within a megalibrary in one experiment. The nanoparticles are spaced at least 1 µm away from its nearest neighbor, and as product is generated at the nanoparticle surface and diffuses outwards, it is trapped by the surrounding molecular probes. The probes thus convert the nanoscale patterns in the megalibrary into micron-sized fluorescent signals that accumulate and amplify catalyst activity for visualization. Taken together, these ultra-high-throughput methods will enable the rapid synthesis of millions of unique and well-defined materials, and the interrogation of each material s catalytic performance. Such unparalleled throughput will accelerate the discovery of electrocatalytic materials, reveal fundamental structure-function relationships, and lay the foundation for discovering new materials that are higher in efficiency, resiliency, and safety, all important to the DoD and ARO.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2023
- Source ID
- W911NF2310285
Entities
People
- Chad Mirkin
Organizations
- Army Contracting Command
- Northwestern University
- United States Army