Rational Synthesis of Alloy Nanocrystals with Controlled Compositions and Facets for Electrocatalysis

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Catalysts consisting of nanoscale metal particles deposited on high-surface-area supports have long been used to promote the rates, product selectivity, and energy efficiency of chemical reactions. However, a long-standing challenge in such heterogeneous catalysis has been the design and synthesis of catalysts that are optimally tuned with respect to particle composition and structure. The project addresses that challenge by developing a precise and robust method for the fabrication of alloy-based electrocatalysts with well-controlled surfaces. The novel synthesis approach will be demonstrated as applied to the direct electrocatalytic conversion of hydrogen (H2) and oxygen (O2) to hydrogen peroxide (H2O2) – thus offering an alternative to energy-intensive and complex current technology. Project results will be further adapted to enhance classroom teaching, including the development of demonstrations (e.g., animations and experiments) related to key concepts in science and engineering. The multi-disciplinary and collaborative nature of the project will offer a vehicle to enrich the education and training experiences of participating students while broadening participation of underrepresented groups in research. Although nanocrystals made of alloys have been extensively explored for a wide variety of electrocatalytic processes, most of the studies reported in the literature are based on a trial-and-error approach that involves labor-intensive screening of numerous alloys in terms of elemental composition and atomic ratio. It is also a grand challenge to quantitatively control the surface of an alloy-based nanocrystal in terms of composition, elemental distribution, and atomic arrangement. With a focus on the electrocatalytic production of hydrogen peroxide, a compound pivotal to a variety of industrial applications, first-principles calculations and data science will be used to identify candidate alloys in terms of composition and surface structure, followed by their faithful translation into nanocrystal-based catalysts through the development of a synthetic method. Different from conventional approaches, solutions of different precursors will be co-titrated dropwise into the reaction solution so that the instantaneous concentration of each precursor is maintained in a predefined steady state throughout the synthesis. As a result, atoms will be produced from the different precursors at stable, pre-specified rates for the generation of alloy nanocrystals with a uniform composition, with the atomic ratio being determined by the reduction rates of their precursors in the steady state. When conformally deposited on nanocrystals with different shapes - as overlayers of a few atomic layers in thickness - alloy-based electrocatalysts with well-defined surfaces and enhanced resistance against elemental segregation will be obtained. The catalytic data from experimental measurements and theoretical predictions will be compared to refine the computational methods while establishing a feedback loop for iterative optimization of the catalysts without involving trial and error. The immediate outcome of this transformative research will be the creation of a knowledge base for the rational development of electrocatalysts featuring an optimal combination of activity, selectivity, and durability toward the electrocatalytic production of hydrogen peroxide. The methods and techniques to be developed can also be extended to accelerate the discovery and development of many other types of nanomaterials with enhanced performance in various applications, including those related to chemical production, petroleum refining, national security, and public health.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.