“…By this mechanism, protons hop via water molecules with a distorted O–H bond. The rate-determining step of the Grotthuss mechanism is reported as the water rotation step272829. The distorted O–H bond species were also observed during ER, as shown in Fig.…”
Section: Kinetic Analyses For Catalytic Steam Reforming (Sr) and Elecmentioning
Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.
“…By this mechanism, protons hop via water molecules with a distorted O–H bond. The rate-determining step of the Grotthuss mechanism is reported as the water rotation step272829. The distorted O–H bond species were also observed during ER, as shown in Fig.…”
Section: Kinetic Analyses For Catalytic Steam Reforming (Sr) and Elecmentioning
Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.
“…A Grotthuss hop is accompanied by a reorganization of the local hydrogen bond network to accommodate the formation of a solvation complex on a new site. Thus, a solvation complex is observed to migrate through the hydrogen bond network, giving rise to a structural diffusion model of proton migration. − 6 Oxygen−oxygen (top) and oxygen−hydrogen (bottom) radial distribution functions for H + in water. The distribution functions are measured with respect to the hydronium oxygen (O*).…”
Section: Hydronium and Hydroxyl Ions In Liquid Watermentioning
Over the past decade, new simulation methodologies, such as the
Car−Parrinello ab initio molecular dynamics
technique, have become increasingly important as tools to study and
characterize condensed phase molecular
systems. We emphasize the versatility of these new approaches to
simulation by reviewing selected applications
to molecular crystals, liquids, and clusters, which highlight a range
of interesting phenomena. The molecular
crystals white phosphorus, nitromethane, and hydrogen chloride
dihydrate exhibit molecular reorientation
phenomena, methyl torsional motion, and proton-hopping events,
respectively. We indicate how, in the latter
examples, it is now possible to include quantum effects in the
simulation of the proton motion. Ionic solvation
and proton transport in water are used to illustrate the current status
of simulations of liquid systems. The
final topic in our survey deals with the possibility of including the
quantum nature of nuclear motions into
the simulation methodology of clusters.
“…From examination of these two idealized current-voltage plots, the basic principle behind the change in E, as a function of 0 2 level scan readily be seen. The exact current-voltage curves for each process can be expressed using the Butler-Volmer equation if all the parameters (e.g., a, k,, A ) are known [14,15]. However, in the case of surface reactions, it is very difficult to obtain accurate values for substitution into the Butler-Volmer formalism, since the required values (especially a, k, and A ) depend on the morphology of the surface which is very difficult to reproduce.…”
The electrochemical response mechanism of a previously reported potentiometric oxygen (0,) sensing system based on thin films of copper sputtered on single crystal Si(100) is examined. The potentiometric 0 2 response of such films is shown to depend on sample stirring rate as well as the pH, ionic strength and nature of the buffer salts within the test solution. XPS studies of the copper films exposed to solution for several days confirm the presence of compper corrosion products on the surface. These findings, in conjunction with cyclic voltammetric measurements, suggest that the potentiometric 0 2 response originates from slow corrosion of copper and simultaneous reduction of 0, -at the surface of the thin films. A steady-state situation exists when the rates of these two reactions are equal, resulting in a corrosion potentlal (also referred as rest potential E, for the system) that varies in a near Nernstian (1 e-) manner with the partial pressure of 0 2 in solution. A mathematical formulation for this type af response, based on the Butler-Volnier equation, is presented. The analytical implications of these findings with respect to devising useful potentiometric O2 sensors based on copper films are discussed.
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