Charge transfer stabilization of late transition metal oxide nano-particles on a layered niobate support
Megan E. Strayer, Thomas Senftle, Jonathan P. Winterstein, Nella M. Vargas-Barbosa, Renu Sharma, Robert M. Rioux, Michael J. Janik, Thomas Mallouk
The interfacial interactions between late transition metal/metal oxide nanoparticles and oxide supports impact catalysts' activity and stability. Here, we report the use of isothermal titration calorimetry (ITC), electron microscopy and density functional theory (DFT) to explore periodic trends in the enthalpy of nanoparticle-support interactions for late transition metal and metal oxide nanoparticles on layered niobate and silicate supports. Data for Co(OH)2, hydroxyiridate-capped IrOx.nH2O, Ni(OH)2, CuO, and Ag2O nanoparticles were added to previously obtained data for Rh(OH)3 grown on nanosheets of TBA0.24H0.76Ca2Nb3O10 and a layered silicate. ITC measurements showed stronger bonding energies in the order Ag < Cu ≈ Ni ≈ Co < Rh < Ir on the niobate support, as expected from trends in M-O bond energies. Nanoparticles with exothermic interaction enthalpy were stabilized against sintering as revealed by electron micros-copy. In contrast, ITC measurements showed endothermic interactions of Cu, Ni, and Rh oxide/hydroxide nanoparticles with the silicate and poor resistance to sintering. These trends in interfacial energies were corroborated by DFT calculations using single-atom and four-atom cluster models of surface-bound metal/metal oxide nanoparticles. Density of states and charge density difference calculations reveal that strongly bonded metals (Rh, Ir) transfer d-electron density from the adsorbed cluster to niobium atoms in the support; this mixing is absent in weakly binding metals, such as Ag and Au, and in all metals on the layered silicate support. The large differences between the behavior of nanoparticles on niobate and silicate supports highlight the importance of d-orbital interactions in controlling their stability.
, Senftle, T.
, Winterstein, J.
, Vargas-Barbosa, N.
, Sharma, R.
, Rioux, R.
, Janik, M.
and Mallouk, T.
Charge transfer stabilization of late transition metal oxide nano-particles on a layered niobate support, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.5b11230, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918971
(Accessed October 21, 2021)