Theoretical prediction by DFT and experimental observation of heterocation-doping effects on hydrogen adsorption and migration over the CeO₂(111) surface

Abstract

The addition of dopants with a small ionic radius led to strong binding of H atoms, and the balance of H+ reactivity (mobility) and H+ coverage was fundamentally important for high H+ conductivity and catalysis involving surface protonics.

Theoretical investigation of selective CO2 capture and desorption controlled by an electric field

“…Results of the present study demonstrated that the surface structure relaxation during adsorption dominates the adsorption behaviour in the adsorption without applying the electric field of CO 2 molecules as well as a recent study about H atom adsorption [20].…”

“…On the other hand, CeO 2 has f electrons and is known as a semi-conductor, so CeO 2 adsorption can be greatly controlled by applying an electric field, and its performance can be easily tuned by hetero-cation doping; since the valence of Ce can be changed, there is a high level of structural freedom through doping with cations of different valence states. Therefore, DFT calculations were performed using CeO 2 doped with various hetero-cations, 20 which have been studied as CO 2 adsorbents 21,22 and as supports for CO 2 -activation catalysts. 23,24 Then, differences between the doped cations were investigated with regard to the changes in the CO 2 adsorption performance by application of the electric field.…”

Effects of A-site composition of perovskite (Sr1−xBaxZrO3) oxides on H atom adsorption, migration, and reaction

“…Reportedly, H atoms tend to join electron-deficient surface oxygen sites because the electron of the H atom can transfer easily to oxygen sites (known as Lewis acid sites). 47,50–52 Therefore, we concluded that the formation of the electron-rich surface oxygens by the subtle Ba 2+ substitution provoked the decrease in the H atom adsorption energy. Furthermore, the obtained DOS shapes (depicted in Fig.…”

“…Previous results verified that activated H atoms over the oxide surface can facilitate N 2 cleavage via unstable species (N 2 H intermediate in the case of NH 3 synthesis) in the electric field. 47 In this mechanism, the formation rate of N 2 H intermediate determines the overall reaction rate. Therefore, the ability of donating H atoms to N 2 is an important factor for NH 3 synthesis in the electric field.…”

“…The binding energies were calibrated with the C 1s peak at 284.8 eV. 24,[45][46][47] Before measurements, the Sr 1Àx Ba x ZrO 3 samples were reduced under H 2 atmosphere (N 2 /H 2 ¼ 1/3, total 240 SCCM) at 723 K for 2 h, which was the same procedure as the activity tests. These samples were transferred to the XPS apparatus without an air exposure using a transfer vessel.…”