CAS-SC: Controlling First and Second Coordination Shells of Earth-abundant Metals to Tune Activity and Stability for Acidic Water Oxidation

About This Grant

With funding support from the Chemical Catalysis program of the Division of Chemistry, Professors Linsey Seitz and Jeffrey Lopez at Northwestern University are investigating fundamental chemistry toward improved hydrogen production via electrochemical water splitting. Hydrogen gas is an important energy carrier and industrial chemical with increasing demand. Proton exchange membrane water electrolysis (PEMWE) is a favorable process for hydrogen production as it has a compact design, minimizes energy losses, and can produce hydrogen at high pressure and purity. However, this technology is expensive, largely due to high loadings of costly platinum group metal (PGM) needed for the process. Widespread PEMWE deployment has not yet been fully realized largely because the development of a commercially viable, stable, and energy-efficient water oxidation catalyst has remained a challenge for decades. The overarching goal of this proposal is to develop and understand the molecular-scale chemistry of inexpensive catalysts that efficiently and durably drive electrochemical water oxidation in PEMWE. This goal will be achieved by designing and implementing advanced automated and experimental probes to characterize catalyst materials under realistic operating conditions in parallel with evaluation of quantitative metrics for structure/performance relationships. Regular meetings with an Industrial Advisory Board will enable critical feedback and guidance to ensure the industrial relevance of ongoing work to the development of PEMWE technologies. In parallel with the research advancements, the PIs will expand electrochemistry-based curriculum at Northwestern University through the development of hands-on laboratory modules to accompany their existing integrated, lecture-based two-course sequence. The combined research and educational efforts will drive novel design and synthesis of efficient and durable catalysts, enhance our understanding of catalytic mechanisms, and develop novel tools and instrumentation for chemical discovery, ultimately advancing the frontiers of chemical science and training a competitive workforce for emerging technologies. Common approaches to catalyst design involve substitution of PGMs or other scarce elements into metal cationic sites of widely explored oxides. Instead, the research team will incorporate inherently Earth-abundant elements into anionic sites creating a library of PGM-free heteroanionic catalyst materials. Tuning the anion dimension of these materials will greatly expand the structural diversity and influence the electronic structure of these materials to offer superior functionality that is inaccessible from chemically simpler homoanionic compounds. The central hypothesis of this proposal is that highly active and durable Earth-abundant water oxidation catalysts can be synthesized and will exhibit enhanced performance through tuning of quantifiable material properties, such as metal valence, anion coordination around metal active sites, and metal cation - anion bond lengths. Along with these material properties, metrics for catalytic activity, material durability, and long-term performance stability will be quantified for every catalyst material tested in this work. The researchers will also exploit material dynamics under controlled reaction conditions to achieve enhanced activity and durability through enhanced fundamental, molecular-level understanding of dynamic catalyst properties. Experimental automation will allow us to perform these carefully designed experiments more quickly and with improved reproducibility, leading to the development of more robust structure-activity and structure-stability descriptors to be identified through our work. Advanced spectroscopic and high throughput analysis will resolve complex catalyst surface reorganization and deactivation mechanisms under controlled reaction conditions. This work will expedite the catalyst discovery and development process to drive transformative enhancements for hydrogen production via PEMWEs based on Earth-abundant catalysts, thereby limiting dependence on scarce and expensive resources. 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.