High-Throughput Studies of Metal Oxide Thin Films for Fuel Cell Applications

Low temperature fuel cells and hydrogen-generating electrolyzers are clean energy technologies with far reaching potential. However, performance is bottlenecked by the slow electrochemical reaction kinetics of oxygen reduction and oxygen evolution. Accelerating the reaction of oxygen currently requires precious metal electrocatalysts, stifling the prospect of widespread fuel cell and electrolyzer proliferation. Consequently, there has been a concerted effort in discovering alternative bifunctional oxygen electrocatalysts, most notably from inexpensive and naturally abundant materials. In particular, complex metal oxides represent a major class of promising new catalyst materials, demonstrating strong catalytic activity and tunability. The sheer breadth of metal oxide systems, underscored by their nearly limitless structural and compositional degrees of freedom, motivates high-throughput synthesis and experimental approaches to expedite and maximize the efficacy of materials discovery. In this study, we performed a range of high-throughput oxygen catalysis measurements on composition-spread libraries of co-sputtered metal oxide thin films. Catalytically active oxides were discovered using a combination of electrochemical screening (cyclic voltammetry, rotating disk electrode, electrochemical impedance, etc.) and versatile high-throughput characterization techniques for structural and compositional mapping. The information from the screening results narrowed the library of potential oxygen catalysts, while identifying novel oxide compounds and structures. The effective translation from thin film to high-surface-area nanoparticle catalysts not only validates the methods utilized in this study, but demonstrates high-throughput electrochemistry as a crucial and complementary approach to catalysis research