(521be) Direct Comparisons of Hydrogen Transfer Electrocatalysis across Molecular and Extended Oxides

Global efforts to decarbonize the chemical industry are directed towards electrification of manufacturing processes. Hydrogen plays a crucial role in industrial manufacturing; making it imperative to understand mechanisms and dynamics of hydrogen transfer through catalytic materials. We are specifically studying hydrogen transfer in redox-active metal oxides as candidates for next-generation catalytic architectures. We are further focusing on probing the inter-relationships between hydrogen transfer electrocatalysis across molecular and extended oxide materials, which we refer to as the “molecules-to-materials design continuum.”

The focus of this presentation will be a comparison of the catalyst activity and selectivity of oxygen reduction reaction (ORR) on tungsten polyoxometalates and tungsten oxide nanoclusters. We have hypothesized that thermal treatment of tungsten polyoxometalates over a range of temperatures will result in the loss of stabilizing ligands and/or counterions with progressive rearrangement into disordered clusters and ultimately crystalline nanoparticles, where each of the accessible forms of the oxide will exhibit different behavior under ORR conditions. The experimental design that we are implementing is as follows:

1. The tungsten polyoxometalates are supported on conductive carbon using electrostatic adsorption, followed by controlled thermal treatments up to 400^oC to progressively evolve the chemical composition from well-defined molecules to well-defined crystalline nanomaterials.
2. The supported catalysts are coated as films on glassy carbon electrodes for ORR measurements under standard conditions using rotating disk and ring-disk electrode voltammetry.
3. Analysis of the ORR linear sweep voltammetry provides information on the ORR rate constants for each catalyst structure as well as its selectivity to 2 versus 4-electron oxygen reduction.

This approach is designed to facilitate direct comparisons between catalytic behavior for molecular clusters and extended solids of mutual similar composition under the overarching hypothesis that these comparisons will reveal important information about the impact of active site composition and electronic structure on H-transfer catalysis.