Proton-Coupled Electron Transfer of Cerium Oxide Nanoparticle Thin-Film Electrodes

Metal oxide (MOx) materials are effective catalysts or cocatalysts in a range of electrochemical reactions and energy systems. A key component of their redox chemistry is proton coupled electron transfer (PCET). Reported here are studies of isolated cerium oxide nanoparticles deposited on fluorine-doped tin oxide (FTO) electrodes with a Langmuir-Blodgett trough and calcined. Cyclic voltammograms of these films showed welldefined, quasi-reversible waves. The E1/2 values moved with pH by -64 +/- 4 mV/pH, close to the ideal Nernstian -59 mV/pH for a 1e-/1H+ couple. These results imply that the electroactive CeO- H bonds had an average bond dissociation free energy (BDFE) of 78.6 +/- 1.5 kcal mol-1. Integration of the faradaic currents indicates that 0.15 +/- 0.04 electrons can be added per cerium atom in the nanoparticle film or similar to 20% of the surface cerium atoms. This study shows how electrochemical investigations can elucidate the stoichiometry and thermochemistry of PCET processes of MOx nanoparticle films. Comparison of these results with those for related ceria nanoparticles shows the remarkable range of properties of this useful material.

Automated summary

Metal oxide (MOx) materials are effective catalysts or cocatalysts in electrochemical reactions and energy systems, and their redox chemistry involves proton coupled electron transfer (PCET). This study investigates isolated cerium oxide nanoparticles deposited on fluorine-doped tin oxide electrodes, finding well-defined, quasi-reversible waves in the cyclic voltammograms of the films. The results reveal the stoichiometry and thermochemistry of the PCET processes of MOx nanoparticle films, and highlight the diverse properties of ceria nanoparticles.