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Chemisorption
About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.
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TL;DR: In this paper, an analysis of X-ray absorption spectroscopy XAS data was performed for fuel cell performance electrocatalytic activities of bimetallics, confirming the role of poisoning of Pt sites in fuel cells.
Abstract: An analysis of X-ray absorption spectroscopy XAS data X-ray absorption near-edge structure XANES and extended X-ray absorption fine structure EXAFS at the Pt L3 edge for Pt‐M bimetallic materials M = Co, Cr, Ni, Fe and at the Co K edge for Pt‐Co is reported for Pt‐M/C electrodes in HClO4 at different potentials. The XANES data are analyzed using the method, which utilizes the spectrum at some potential V minus that at 0.54 V reversible hydrogen electrode RHE representing a reference spectrum. These data provide direct spectroscopic evidence for the inhibition of OH chemisorption on the cluster surface in the Pt‐M. This OH chemisorption, decreasing in the direction Pt Pt‐Ni Pt‐Co Pt‐Fe Pt‐Cr, is directly correlated with the previously reported fuel cell performance electrocatalytic activities of these bimetallics, confirming the role of OH poisoning of Pt sites in fuel cells. EXAFS analysis shows that the prepared clusters studied have different morphologies, the Pt‐Ni and Pt‐Co clusters were more homogeneous with M atoms at the surface, while the Pt‐Fe and Pt‐Cr clusters had a “Pt skin.” The cluster morphology determines which previously proposed OH inhibition mechanism dominates, the electronic mechanism in the pres
145 citations
TL;DR: CAC-5 (modified AC) exhibits better CO2 adsorption performance, which can be attributed to the formation of the CO2-philic active sites on AC surface by N-species, and the high IAST selectivity factor for N-doped ACs indicates their excellent Adsorption selectivity for CO2 over N2.
145 citations
TL;DR: In this paper, the authors studied the kinetics and mechanism of oxidation of carbon atoms exposed at monolayer steps on graphite surface and two pieces of direct evidence are shown for the importance of surface diffusion in the overall kinetics.
Abstract: The kinetics and mechanism of oxidation of carbon atoms exposed at monolayer steps on graphite surface have been studied with the etch‐decoration and transmission electron microscopy technique and two pieces of direct evidence are shown for the importance of surface diffusion in the overall kinetics. It is found that the rate of carbon removal, or the turnover frequency, depends on the population density of these edge carbon atoms, being substantially higher on low‐density surfaces. In the argon flush experiment, it is found that surfaces with low edge carbon densities continue to ’’burn’’ for prolonged periods of time after O2 is cut off from the gas phase. Two independent mechanisms are revealed by the experimental results: (1) reaction resulted from direct collision of O2 on the edge carbon, and (2) reaction of the edge carbon with the migrated oxygen which is first chemisorbed on the basal carbon. Furthermore, from the results of the argon flush experiments, the following results can be calculated: surface diffusion coefficient = 5×10−12 cm2/s (for O/C = 0.34) and 2×10−12 cm2/s (for O/C = 0.06); rate constant for the edge carbon reacting with the migrated O atom = 4.5 s−1, all at 650 °C. The amount of chemisorption on the basal plane can also be obtained from the data of the argon flush technique as demonstrated in this work.
145 citations
TL;DR: In this paper, the authors showed that hydrogen can be desorbed from ceria as reversible adsorption and reversible adaption depending on the reduction temperature, and that H2 was the only desorption product.
Abstract: The chemisorption of hydrogen on two ceria samples (CeO2-BS, 4 m2 g–1; CeO2-SM, 56 m2 g–1) reduced at temperatures ranging from 623 to 1173 K has been studied by Fourier-transform infrared (FTIR) spectroscopy and temperature-programmed desorption followed by thermal conductivity (TPD-TC) and mass spectrometry (TPD-MS). The concentration of the oxygen vacancies created by the reduction treatments was determined by using a combination of O2 pulses and temperature-programmed oxidation. According to our TPD-MS study, hydrogen can be desorbed from ceria as both H2(reversible adsorption) and H2O (irreversible adsorption), the relative contribution of these two forms depending on the reduction temperature. For samples reduced at 773 K or higher temperatures, H2 was the only desorption product. From this observation, some earlier TPD-TC and TPR-TC results could be better understood. Upon reduction at 773 K, the amount of H2 chemisorbed per mole of CeO2 was ten times larger for CeO2-SM than for CeO2-BS. Likewise, the molar chemisorptive capability of CeO2-SM strongly decreased (45 times) with the reduction temperature. No simple relationship could be observed between the amount of chemisorbed hydrogen and the total concentration of oxygen vacancies in the oxide. In contrast to earlier results on the contribution of a massive bronze-like phase when chemisorbing H2 at 195–500 K, the results reported here show that the hydrogen chemisorption on reduced ceria is a surface-related process. Furthermore, the highest value for the hydrogen chemisorption we have obtained, 7.1 H atom nm–2(BET), suggests a pure surface process.
145 citations
TL;DR: In this paper, the decomposition of NO has been studied in a flow reactor on oxides of iron, cobalt, nickel, copper, and zirconium as well as on supported platinum at 780-960 Torr between 450 and 1000 °C.
144 citations