CAS: Rational Design of Earth-Abundant Phosphide Hydrogen Evolution Catalysts

Iowa State University, Ames IA

Investigators

Abstract

With funding from the Chemical Catalysis Program of the Division of Chemistry, Drs. Kovnir and Johnson from Iowa State University are addressing a key socioeconomic problem: the strong dependence on fossil fuels. To that end, their research groups are studying the production of hydrogen from water via electrolysis. To produce hydrogen efficiently and economically by electrolysis improved electrode materials, known as electrocatalysts, are needed. This joint experimental and computational project is providing a fundamental understanding of how electrocatalysts with well-defined properties and structures can be modified to enhance their performance. Their collaborative and integrative synthetic, structural, and surface studies of electrocatalysts are providing a unique training and educational experience for student researchers. Students involved in the project include undergraduate and high-school students. Drs. Kovnir and Johnson are also engaged in broadening participation of underrepresented minorities in their research, including for example the ACS Summer Research Internship Program for Economically Disadvantaged High School Students. Dr. Kovnir is developing summer research projects to for undergraduate on sustainable materials and the undergraduate and graduate students are learning how to communicate science to the public through the Chemistry Learning Community outreach. Hydrogen is a sustainable fuel that is currently produced by catalyzed steam reforming (and burning of methane), which compromises all environmental benefits. Releasing hydrogen via catalytic electrolysis of water, if coupled with renewable energy sources, is a future solution to this issue. Although heterogeneous catalysts accounts for 20% of the Gross World Product, to be sustainable and cheap, electrocatalysts based on earth-abundant elements are required. Recently, nanoparticle phosphides formed with abundant first-row transition-metals (Iron or Nickel) have been shown to be promising electrocatalysts for the hydrogen evolution reaction (HER). The surface of these electrocatalytic nanoparticles is difficult to control precisely and characterize, because each crystal facet on a nanoparticle has different atomic bonding and reactivity. Unsurprising then, with many facets participating in reactions, there is lack of fundamental understanding as to why some catalysts are better than others, and, more often than not, serendipity discovers new catalysts. Given that the structure of each surface facet is defined by the crystal structure of the bulk phase, Drs. Kovnir and Johnson of Iowa State University are studying the electronic behavior of the surface-active sites by the alternation of chemical bonding patterns in the bulk transition-metal phosphides. Fundamental relationships are being established between bulk structure, in-situ surface (crystal facet-dependent) structure, and electrocatalytic performance of model transition-metal–phosphide catalysts with tunable reactivities. With funding from the Chemical Catalysis Program in the Division of Chemistry these studies will aid progress toward the discovery of improved, cheaper, and environmentally sustainable HER electrocatalysts. Drs. Kovnir and Johnson are actively engaged in student participation in their research, including high school and undergraduate students, and students from underrepresented groups. Summer research and science communication opportunities are also being provided for these students. 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.