Chemisorption

About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.

Atomic and molecular adsorption on Rh(111)

Abstract: A systematic study of the chemisorption of both atomic (H, O, N, S, C), molecular (N2, CO, NO), and radical (CH3, OH) species on Rh(111) has been performed Self-consistent, periodic, density functional theory (DFT-GGA) calculations, using both PW91 and RPBE functionals, have been employed to determine preferred binding sites, detailed chemisorption structures, binding energies, and the effects of surface relaxation for each one of the considered species at a surface coverage of 025 ML The thermochemical results indicate the following order in the binding energies from the least to the most strongly bound: N2

Activated TiO2 with tuned vacancy for efficient electrochemical nitrogen reduction

Abstract: Renewable energy-driven electrochemical N2 reduction reaction (NRR) provides a green and sustainable route for NH3 synthesis under ambient conditions but is plagued by a high reaction barrier and low selectivity. To promote NRR, modification of the catalyst surface to increase N2 adsorption and activation is key. Here, we show that engineering surface oxygen vacancies of TiO2 permits significantly enhanced NRR activity with an NH3 yield rate of about 3.0 μgNH3 h−1 mgcat.−1 and a faradaic efficiency (FE) of 6.5% at -0.12 V (vs. the reversible hydrogen electrode, RHE). Efficient conversion of N2 to NH3 is achieved in a wide applied potential range from -0.07 to -0.22 V (vs. RHE) with NH3 production rates ≥ 2.0 μgNH3 h−1 mgcat.-1 and NH3 FEs ≥ 4.9%, respectively. An NH3 FE as high as 9.8% is obtained at a low overpotential of 80 mV. Density functional theory calculations reveal that the surface oxygen vacancies in TiO2 play a vital role in facilitating electrochemical N2 reduction by activating the first protonation step and also increasing N2 chemisorption (relative to *H).

Thermal ageing of Pt on low-surface-area CeO2-ZrO2-La2O3 mixed oxides : Effect on the OSC performance

Abstract: This work aims at exploring the thermal ageing mechanism of Pt on ceria-based mixed oxides and the corresponding effect on the oxygen storage capacity (OSC) performance of the support material. Pt was supported on low-surface-area CeO2–ZrO2–La2O3 mixed oxides (CK) by impregnation method and subsequently calcined in static air at 500, 700 and 900 °C, respectively. The evolutions of textural, microstructural and redox properties of catalysts after the thermal treatments were identified by means of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) and high-resolution transmission electron microscope (HRTEM). The results reveal that, besides the sintering of Pt, encapsulation of metal by the mixed oxides occurs at the calcination temperature of 700 °C and above. The burial of Pt crystallites by support particles is proposed as a potential mechanism for the encapsulation. Further, the HRTEM images show that the distortion of the mixed oxides lattice and other crystal defects are distributed at the metal/oxides interface, probably indicating the interdiffusion/interaction between the metal and mixed oxide. In this way, encapsulation of Pt is capable to promote the formation of Ce3+ or oxygen vacancy on the surface and in the bulk of support. The OSC results show that the reducibility and oxygen release behavior of catalysts are related to both the metal dispersion and metal/oxides interface, and the latter seems to be more crucial for those supported on low-surface-area mixed oxides. Judging by the dynamic oxygen storage capacity (DOSC), oxygen storage capacity complete (OSCC) and oxygen releasing rate, the catalyst calcined at 700 °C shows the best OSC performance. This evident promotion of OSC performance is believed to benefit from the partial encapsulation of Pt species, which leads to the increment of Ce3+ or oxygen vacancies both on the surface and in the bulk of oxides despite a loss of chemisorption sites on the surface of metal particles.