The major goal of this proposal is to develop highly efficient ultra-low noble metal content (e.g. Pt, IrO₂, RuO₂) and noble metal and even precious group metal free (PGM-free) oxygen evolution reaction (OER) electrocatalyst for proton exchange membrane (PEM) based acid mediated water electrolysis. This in turn will reduce the capital cost while significantly improving the efficiency (≤43kWh/kg H₂) than the state-of-the art commercial PGM based PEM electrolyzers and expectedly meeting the hydrogen production cost goal ($2/Kg H₂). In the direction of developing highly active and efficient ultra-low noble metal and PGM-free electrocatalysts, the fundamental relationships between the electrocatalyst atomic level crystal structure and compositions on the electrocatalyst surface as well as within the bulk, and surface related electrochemical properties have been correlated to understand the fundamental structure-property relationships in the 2D thin film system. In this direction, first principles based theoretical calculation (e.g. density functional theory, DFT) has been utilized to identify the suitable electrocatalysts and compositions followed by advanced experimental electrocatalyst synthesis, and characterization. Such atomic and electronic structure-property relationships is very helpful for the identification, design and synthesis of suitable electro-catalysts in 0D, 1D and 3D nanostructured dimensions and configurations as well as in the preferred oriented crystallographic state. The processing-structure-property correlations will also serve to ultimately develop low cost PGM-free based electro-catalysts. The theoretical and experimental studies will thus work synergistically to determine not only the bulk and surface atomic and electronic level structures and compositions that are effective in terms of electrocatalytic response but also help to understand the underlying detailed mechanisms contributing to the electrocatalytic activity.. Understanding of the mechanisms will then serve to effectively fine tune and design the electrocatalyst system helping to unravel the fundamental pathways leading to the identification of PGM-free commercially viable electrocatalyst for PEM based acid mediated electrolyzers.

In order to understand the process/synthesis-atomic/electronic structure-electrochemical property relationships, a fundamental theoretical and experimental study has been conducted to integrate theory, modeling, synthesis, structural and electrochemical characterization of the electrocatalysts to advance the science and technology of electrocatalysts. In this direction, theoretically predicted F doped (Mn,Ir)O₂:F, (Sn,Ir)O₂:F, and (Sn,Nb,Ir)O₂:F have been synthesized in 2D thin film and suitable correlation between processing-structure property have been developed. The theoretical and experimental outcomes and understandings of structure-property relationship of 2D thin film obtained has been utilized to synthesize highly active low overpotential electrocatalysts in different "materials length scales" e. g. vertically aligned 1D nanorod/nanotube structure of (Sn,Ir)O₂:F and (Mn,Ir)O₂:F were synthesized which expedite the reaction kinetics resulting in superior electrocatalytic activity towards water splitting compared to the 2D structures. Low noble metal containing 1D nanotube of (Mn,Ir)O2:10F and (Sn,Ir)O2:F solid solution indeed show excellent promise for replacing the state of the art OER electro-catalysts IrO2/RuO2 on the grounds of its excellent electrochemical performance. This study portends significant reduction in noble metal content for OER electro-catalyst along with a significant improvement in electrochemical activity. Together, these will be of immense help in reducing the capital cost of water electrolysis cells for economic and efficient hydrogen production from acid based PEM water electrolysis for meeting the incessantly growing global energy demands, employing non-carbonaceous clean energy source in an efficient and economic manner.

The 2D thin film data has also been utilized to synthesize for the very first time highly active low overpotential 3D nanostructured non noble metal containing Cu-Mn-oxides based PGM-free electrocatalyst. In addition, PGM-free F doped cobalt nickel phosphide (CoNiP:F), and Mn-metal oxide electro-catalyst were computationally identified and experientially validated for oxygen evolution reaction (OER) for PEM water electrolysis,. The first-principles calculations of the total energies and electronic structures identified Co-Ni-P and Mn-metal oxide based electro-catalysts. Both F doped CoNiP and Mn-metal oxide were thus explored as high performance electro-catalysts possessing unique electronic structures mimicking the PGM electrocatalysts. Development of PGM-free electrocatalyst marks a hallmark advancement in the identification and development of novel noble metal-free 0D and 3D nanostructured electro-catalysts (Cu-Mn-oxide, CoNiP and Mn metal-oxide) possessing unique electronic/molecular structure exhibiting remarkable stability and outstanding electrochemical activity higher than IrO2 for OER, the currently accepted gold standard electro-catalysts. Hence, these systems can replace IrO2 with possible further modification leading to further improvements. In the opinion of the PIs, the system represents a fundamental breakthrough in the pursuit of PGM-free electrocatalysts for economic and efficient hydrogen production from acid based PEM water electrolysis, while also enabling proficient power generation from fuel cells (PEMFCs, DMFCs). The experimental results obtained in this project validate the theoretical predictions thus serving as a pathway for not only identifying new commercially viable electrocatalysts with significant reduction in noble metal content but also even completely eliminating use of any precious metals. The project thus has significant potential for advancing the science and technology of PGM-free electrocatalysts for acid mediated PEM based water electrolysis..

Last Modified: 01/17/2019
Modified by: Prashant N Kumta