Development of an O2-Sensitive Fluorescence-Quenching Assay for the Combinatorial Discovery of Electrocatalysts for Water Oxidation

摘要

Electrochemical water oxidation is a major focus of solar energy conversion efforts. This anodic half-reaction affords electrons and protons needed to achieve fuel production by reduction of water, CO2, or other abundant feedstocks at the cathode of a photoelectrochemical cell (PEC; Figure 1). High kinetic barriers associated with the oxidation of water to O2 and the common use of high-cost electrocatalytic materials are among the challenges that limit the utility of photoelectrochemical energy storage. Improved electrocatalysts that operate at lower overpotential and avoid the use of expensive precious-metal or rare-earth elements are needed. While valuable progress is being made toward this goal, the rational design of optimal catalysts from first principles remains infeasible, and the number of possible catalyst compositions, even those with well-defined metal stoichio-metry, far exceeds the number that can be tested in a traditional sequential fashion. Combinatorial methods can play an important role in the discovery of new electrocatalysts, and we describe herein a fluorescence-based assay for spatially resolved, direct detection of O2 across an array of metal-oxide electrocatalysts. Initial implementation of this technique has led to the identification of new electrocatalysts, which are composed entirely of earth-abundant elements (e.g., Ni/Al/ Fe) and warrant further investigation.