A study of the catalytic activity of platinum. examination of surface oxygen species by photoelectron spectroscopy

Vacuum ◽  
1976 ◽  
Vol 26 (4-5) ◽  
pp. 211
Author(s):  
Meng Wang ◽  
Yan Zhang ◽  
Yunbo Yu ◽  
Wenpo Shan ◽  
Hong He

Herein, transition metal (Mn and Fe)-doped Ce–Sn nanorod catalysts were successfully synthesized via a hydrothermal method.


1996 ◽  
Vol 454 ◽  
Author(s):  
Y. Kanai ◽  
H. Ichimura ◽  
H. Kawakami

ABSTRACTThe direct decomposition of NO (2NO → N2+02) has been carried out using an electrochemical membrane reactor composed of an yttria-stabilized zirconia (YSZ) disc deposited with Pd and Au metal films at reaction temperature of 773∼1023 K and applying voltage of 0∼1.8 V. N2 and O2 were continuously produced in the cathode and anode chambers, respectively. NO decomposition activity increased by applying electrical potential. It was clearly shown that the enhancement of the catalytic activity was due to electrochemical pumping, by which the surface oxygen species formed by the dissociation of NO were transported from cathode to anode through YSZ. By comparing the catalytic activity between Pd/YSZ/Au and Au/YSZ/Au systems, it is suggested that the NO decomposition occurs mainly on the Pd surface, and YSZ itself did not catalyze the reaction at lower temperature. The rate-determining step for the reaction was the adsorption of NO at 973 K, while at 773 K, the step was either a diffusion of O2- in YSZ or a migration of surface oxygen species on the Pd surface. The surface observation of Pd films by SEM showed that many microvoids were created throughout the Pd surface after the reaction. The creation of the microvoids results in an increase in the number of three-phase boundary sites, which will play an important role for the enhancement of the NO decomposition. Moreover, it was found that Pd/YSZ/Au resisted a serious degradation of the activity in the presence of O2 in the feed stream.


2020 ◽  
Vol 1 (1) ◽  
pp. 38-42
Author(s):  
Jun Yan

Cu-supported nano-TiO2 catalyst was prepared by forced hydrolysis method under mild condition. The morphology, composition and optical absorption properties of the samples were characterized by means of scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy (UV-VIS DRS). Visible photocatalytic activity of the samples was investigated by photocatalytic degradation experiment on methyl orange. The results indicated that nano-TiO2 was about 20nm in size with the main form of anatase, and photo response range was significantly broadened after it was loaded on the surface of Cu. The sample possessed high visible light catalytic activity, with the degradation rate of methyl orange reaching 94% under simulated natural light.


2016 ◽  
Vol 73 (11) ◽  
pp. 2747-2753 ◽  
Author(s):  
Wusong Kong ◽  
Hongxia Qu ◽  
Peng Chen ◽  
Weihua Ma ◽  
Huifang Xie

In this study, Cu2O-CuO/ZSM-5 nanocomposite was synthesized by the impregnation method, and its catalytic performance for the destruction of AO7 in aqueous solutions was investigated. The morphology, structure and surface element valence state of Cu2O-CuO/ZSM-5 were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The operating conditions on the degradation of AO7 by Cu2O-CuO/ZSM-5, such as initial pH values, concentration of AO7 and catalyst dosage were investigated and optimized. The results showed that the sample had good catalytic activity for destruction of AO7 in the absence of a sacrificial agent (e.g. H2O2): it could degrade 91% AO7 in 140 min at 25 °C and was not restricted by the initial pH of the AO7 aqueous solutions. Cu2O-CuO/ZSM-5 exhibited stable catalytic activity with little loss after three successive runs. The total organic carbon and chemical oxygen demand removal efficiencies increased rapidly to 69.36% and 67.3% after 120 min of treatment by Cu2O-CuO/ZSM-5, respectively.


Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2115 ◽  
Author(s):  
Anna Ilnicka ◽  
Malgorzata Skorupska ◽  
Piotr Romanowski ◽  
Piotr Kamedulski ◽  
Jerzy P. Lukaszewicz

The constantly growing demand for active, durable, and low-cost electrocatalysts usable in energy storage devices, such as supercapacitors or electrodes in metal-air batteries, has triggered the rapid development of heteroatom-doped carbon materials, which would, among other things, exhibit high catalytic activity in the oxygen reduction reaction (ORR). In this article, a method of synthesizing nitrogen-doped graphene is proposed. Few-layered graphene sheets (FL-graphene) were prepared by electrochemical exfoliation of commercial graphite in a Na2SO4 electrolyte with added calcium carbonate as a separator of newly-exfoliated FL-graphene sheets. Exfoliated FL-graphene was impregnated with a suspension of green algae used as a nitrogen carrier. Impregnated FL-graphene was carbonized at a high temperature under the flow of nitrogen. The N-doped FL-graphene was characterized through instrumental methods: high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical performance was determined using cyclic voltamperometry and linear sweep voltamperometry to check catalytic activity in ORR. The N-doped electroexfoliated FL-graphene obeyed the four-electron transfer pathways, leading us to further test these materials as electrode components in rechargeable zinc-air batteries. The obtained results for Zn-air batteries are very important for future development of industry, because the proposed graphene electrode materials do not contain any heavy and noble metals in their composition.


Catalysts ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 375
Author(s):  
Adele R. Latypova ◽  
Maxim D. Lebedev ◽  
Evgeniy V. Rumyantsev ◽  
Dmitry V. Filippov ◽  
Olga V. Lefedova ◽  
...  

The article describes the synthesis of aminoorgano-functionalized silica as a prospective material for catalysis application. The amino groups have electron donor properties which are valuable for the metal chemical state of palladium. Therefore, the presence of electron donor groups is important for increasing catalysts’ stability. The research is devoted to the investigation of silica amino-modified support influence on the activity and stability of palladium species in 4-nitroaniline hydrogenation process. A series of catalysts with different supports such as SiO2, SiO2-C3H6-NH2 (amino-functionalized silica), γ-Al2O3 and activated carbon were studied. The catalytic activity was studied in the hydrogenation of 4-nitroaniline to 1,4-phenylenediamine. The catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and chemisorption of hydrogen by the pulse technique. The 5 wt.% Pd/SiO2-C3H6-NH2 catalyst exhibited the highest catalytic activity for 4-nitroaniline hydrogenation with 100% conversion and 99% selectivity with respect to 1,4-phenylenediamine.


NANO ◽  
2020 ◽  
Vol 15 (02) ◽  
pp. 2050018
Author(s):  
Cai Chen ◽  
Han Zhang ◽  
Arshid M. Ali ◽  
Hui Zhang

Oxygen defects of nanoflower TiO2 photo-catalyst was fabricated at the presence of hydrogen at different temperatures (100–600∘C) and the concentrations of oxygen defects were firstly quantitatively analyzed by hydrogen programmed temperature reduction techniques (H2-TPR). Total oxygen defect concentration and surface oxygen defect concentration were consistent with XPS and EPR results, respectively. Even at the hydrogen thermal temperature of 600∘C, the shape of TiO2 was still kept as nanoflower structure as characterized by SEM. However, the rutile and anatase coexist in the composition of crystal phase when hydrogen reduction temperature of the TiO2 catalyst reached 400∘C to 600∘C as proved by Raman and XRD results. TiO2 sample with oxygen defects shows excellent photo-catalytic activity for degradation of Direct Blue 78(DB) regardless of ultraviolet light (the maximum degradation rate achieved within 100[Formula: see text]min was 93.27%) or visible light (the maximum degradation rate achieved within 100[Formula: see text]min was 88.25%). The photo-catalytic activity seems to be highly correlated with the surface oxygen defects of TiO2 catalyst. With surface oxygen-defect concentrations increase, the degradation ability on DB was significantly enhanced, while bulk oxygen defects had negligible effect on the photo-catalytic activity. The enhanced photo-catalytic performance of TiO2 with a fixed amount of oxygen defects was attributed to the strong capturing capability of the photo-generated electrons. In addition, the surface defects could also improve the photo-catalytic reaction efficiency.


Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 342 ◽  
Author(s):  
Yuji Ohkubo ◽  
Tomonori Aoki ◽  
Satoshi Seino ◽  
Osamu Mori ◽  
Issaku Ito ◽  
...  

In a previous study, Pt nanoparticles were supported on a substrate of acrylonitrile–butadiene–styrene copolymer (ABS) to give the ABS surface catalytic activity for H2O2 decomposition during contact lens cleaning. Although the Pt-particle/ABS catalysts exhibited considerably high specific catalytic activity for H2O2 decomposition, the catalytic activity decreased with increasing numbers of repeated usage, which meant the durability of the catalytic activity was low. Therefore, to improve the catalytic durability in this study, we proposed two types of pretreatments, as well as a combination of these treatments before supporting Pt nanoparticles on the ABS substrate. In the first method, the ABS substrate was etched, and in the second method, the surface charge of the ABS substrate was controlled. A combination of etching and surface charge control was also applied as a third method. The effects of these pretreatments on the surface morphology, surface chemical composition, deposition behavior of Pt particles, and Pt loading weight were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cross-sectional SEM, and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. Both etching and controlling the surface charge effectively improved the catalytic durability for H2O2 decomposition. In addition, the combination treatment was the most effective.


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