Proton-coupled electron transfer reactions of nanoscale materials

Redox reactions across the interface between a solid and a solution are ubiquitous in the environment and in many technologies. These are usually discussed as pure electron transfer processes, but our laboratory has recently shown that these reactions can be proton-coupled electron transfers. It is our hypothesis that protons are often key components of redox chemistry of these nanocrystals, and that the coupling of the electrons with protons is a common and important component of many processes, although currently underappreciated.

We are working mostly with colloidal metal oxide nanocrystals, including ZnO, TiO2 and CeO2, as well as molybdenum nitride (Mo2N). These colloidal materials can be studied using many of the techniques of molecular chemistry, such as titrations and optical, NMR, and EPR spectroscopies. We are also using materials characterization techniques such as x-ray diffraction and electron microscopy. We are exploring inner-sphere reactions of these materials, redox reactions that involve bond making and bond breaking, for instance O–H bonds at the surface of a metal oxide. We are examining the stoichiometries and mechanisms of these novel reactions. What we learn from these fundamental studies should be relevant to a wide range of applications.

Relevant Publications

Peper, J. L.; Gentry, N. E.; Boudy, B.; Mayer, J. M.
Aqueous TiO2 Nanoparticles React by Proton-Coupled Electron Transfer
Inorg. Chem.  202261, 767–777.  
Agarwal, R. G.; Coste, S. C.; Groff, B. D.; Heuer, A. M.; Noh, H.; Parada, G. A.; Wise, C. F.; Nichols, E. M.; Warren, J. J.; Mayer, J. M.
Free Energies of Proton-Coupled Electron Transfer Reagents and Their Applications
Chem. Rev.  2022122, 1-49.  
Agarwal, R. G.; Kim, H.-J. Mayer, J. M.
Nanoparticle O-H Bond Dissociation Free Energies from Equilibrium Measurements of Cerium Oxide Colloids
J. Am. Chem. Soc.  2021143, 2896-2907.  
Peper, J. L.; Gentry, N. E.; Brezny, A. C.; Field, M. J.; Green, M. T.; Mayer, J. M.
Different Kinetic Reactivity of Electrons in Distinct TiO2 Nanoparticle Trap States
J. Phys. Chem. C  2021125, 680–690.  
Castillo-Lora, J.; Delley, M. F.; Laga, S. M.; Mayer, J. M.
Two-Electron–Two-Proton Transfer from Colloidal ZnO and TiO2 Nanoparticles to Molecular Substrates
J. Phys. Chem. Lett.  202011, 7687-7691.  
Valdez, C.N., Delley, M.F., Mayer, J.M.
Cation Effects on the Reduction of Colloidal ZnO Nanocrystals
J. Am. Chem. Soc.  2018140, 8924-8933.  
Ghosh, S., Castillo-Lora, J., Soudackov, A.V., Mayer, J.M.; Hammes-Schiffer, S.
Theoretical Insights into Proton-Coupled Electron Transfer from a Photoreduced ZnO Nanocrystal to an Organic Radical
Nano Lett.  201719, 5762-5767.  
Peper, J. L.; Vinyard, D. J.; Brudvig, G. W.; Mayer, J. M.
Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO2 Nanoparticles
J. Am. Chem. Soc.  2017139, 2868-2871.  
Damatov, D.; Mayer, J.M.
(Hydro)peroxide ligands on colloidal cerium oxide nanoparticles
Chem. Commun.  201652, 10281-10284.  
Valdez, C.N.; Schimpf, A.M.; Gamelin, D.R.; Mayer, J.M.
Proton-Controlled Reduction of ZnO Nanocrystals: Effects of Molecular Reductants, Cations, and Thermodynamic Limitations
J. Am. Chem. Soc.  2016138, 1377-1385.  
Valdez, C. N.; Schimpf, A. N.; Gamelin, D. R. Mayer, J. M.
Low Capping Group Surface Density on Zinc Oxide Nanocrystals
ACS Nano   20148, 9463–9470.  
Valdez, C.N.; Braten, M.; Soria, A.; Gamelin, D.R.; Mayer, J.M.
Effect of Protons on the Redox Chemistry of Colloidal Zinc Oxide Nanocrystals
J. Am. Chem. Soc.   2013135, 8492-8495.  
Schrauben, J.N.; Hayoun, R.; Valdez, C.N.; Braten, M.; Fridley, L.; Mayer, J.M.
Titanium and Zinc Oxide Nanoparticles are Proton-Coupled Electron Transfer Agents
Science  2012336, 1298-1301.