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1.
To realize renewable energy conversion,it is important to develop low-cost and high-efficiency electrocatalyst for oxygen evolution reaction.In this communication,a novel bijunction CoS/CeO 2 electrocatalyst grown on carbon cloth is prepared by the interface engineering.The interface engineering of CoS and CeO 2 facilitates a rapid charge transfer from CeO 2 to CoS.Such an electrocatalyst exhibits outstanding electrocatalytic activity with a low overpotential of 311 mV at 10 mA·cm?2 and low Tafel slope of 76.2 mV·dec?1,and is superior to that of CoS(372 mV)and CeO 2(530 mV)counterparts.And it has long-term durability under alkaline media. 相似文献
2.
The influence of 30% (v/v) organic cosolvent in 1.0 mol dm –3 HClO 4 on the OER electrode kinetics, surface properties and electrode stability of IrO 2-based electrodes was investigated by cyclic voltammetry and polarization curves. The Tafel coefficients in the presence of cosolvent are explained in terms of the change of the rate-determining step (r.d.s.) of the OER electrode mechanism, coating dissolution and/or cosolvent oxidation. Of the several cosolvents investigated t-BuOH and PC show less effects on the OER and electrode properties making them the best choice for organic eletrosynthesis applications, in contrast to AN, which causes coating dissolution, and DMF and DMSO which show an anticipation of the voltammetric current. 相似文献
3.
Using renewable energy to electrolyze water to produce hydrogen is the only way to realize a green hydrogen economy. At present, the large-scale application of this technology is encumbered by the relatively low activity and stability of oxygen evolution reaction (OER) electrocatalysts. The use of cost-effective catalysts can significantly reduce the overpotential of oxygen evolution and improve the economics and power conversion efficiency of the hydrogen production process from electrolysis of water. Among the various candidates, the transition metal oxide-based (TMOs) materials show great prospects and receive ever-increasing research interests because of their diversified surface/bulk structures, natural enrichment, easy accessibility and environmental friendliness. In this review, the latest tactics aiming at enhancing activity via increasing the accessible active sites and promoting intrinsic activity have been summarized. In addition, with special emphasis on the long-term stability, the up-to-data strategies for elevating the stability are introduced. Finally, conclusions and perspectives are also presented. 相似文献
4.
利用可再生能源电解水制氢,是实现绿色氢能经济的必由之路。现阶段,电解水过程的阳极析氧反应过电位较高,催化剂性能不稳定,制约着该技术的工业化应用。使用经济高效的催化剂,可显著降低析氧过电位,提高电解水制氢过程的经济性和电能转化效率。在各类析氧催化剂材料中,过渡金属氧化物(TMOs)由于晶体结构多样、储量丰富、环境友好、易于制备以及活性较高等优点,受到了越来越多的关注。本文从活性和稳定性出发,总结分析了近年来过渡金属氧化物催化析氧反应的研究进展,并对其未来的发展提出了建议与展望。 相似文献
5.
以六水合硝酸钴、六水合硝酸镍、尿素和氟化铵为原料,采用水热法在镍网上原位构筑层状双金属氢氧化物(LDH)(CoNi-LDH@NF),然后采用快速界面法在硝酸钠和六水合氯化铁的100℃溶液中对其进行刻蚀制备了FeOOH@CoNi-LDH@NF.利用XRD、SEM、XPS和TEM对FeOOH@CoNi-LDH@NF进行了形... 相似文献
6.
Recently, metal–organic frameworks are one of the potential catalytic materials for electrocatalytic applications. The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory. Firstly, the catalytic activities of heterometallic clusters are investigated. Among all heterometallic clusters, Fe 2Mn–Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction, and Fe 2Co–Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction, respectively 100 and 50 mV lower than those of Pt(111) and RuO 2(110) catalysts. The analysis of the potential gap of Fe 2M clusters indicates that Fe 2Mn, Fe 2Co, and Fe 2Ni clusters possess good bifunctional catalytic activity. Additionally, the catalytic activity of Fe 2Mn and Fe 2Co connected through 3,3′,5,5′-azobenzenetetracarboxylate linker to form Fe 2M–PCN–Fe 2M is explored. Compared with Fe 2Mn–PCN–Fe 2Mn, Fe 2Co–PCN–Fe 2Co, and isolated Fe 2M clusters, the mixed-metal Fe 2Co–PCN–Fe 2Mn possesses excellent bifunctional catalytic activity, and the values of potential gap on the Mn and Co sites of Fe 2Co–PCN–Fe 2Mn are 0.69 and 0.70 V, respectively. Furthermore, the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst. In conclusion, the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts. 相似文献
7.
电解水制氢是绿色氢能源研究中的热点课题。其中,析氧半反应较高的过电位是导致电解水动力学缓慢的主要原因。为了提高电解水制氢的效率,本文主要通过简单的液相合成方法,以硼氢化钠和过渡金属Ni,Fe,Co盐为原料,制备了非晶态的过渡金属硼化物Ni-Fe-Co-B,将其作为析氧半反应催化剂。对Ni-Fe-Co-B进行了SEM、TEM、XRD、XPS和电化学表征。结果表明,非晶态催化材料Ni-Fe-Co-B被成功合成,当n(Ni)∶n(Fe)∶n(Co)=1∶1∶1,电流密度为20 mA/cm2时,Ni-Fe-Co-B的过电位仅为299 mV,Tafel斜率为101 mV/dec。在0.47 V的恒电压测试下,Ni-Fe-Co-B具有12h以上的稳定性。 相似文献
8.
High-performance and ultra-durable electrocatalysts are vital for hydrogen evolution reaction (HER) during water splitting. Herein, by one-pot solvothermal method, MoO x/Ni 3S 2 spheres comprising Ni 3S 2 nanoparticles inside and oxygen-deficient amorphous MoO x outside in situ grow on Ni foam (NF), to assembly the heterostructure composites of MoO x/Ni 3S 2/NF. By adjusting volume ratio of the solvents of ethanol to water, the optimized MoO x/Ni 3S 2/NF-11 exhibits the best HER performance, requiring an extremely low overpotential of 76 mV to achieve the current density of 10 mA∙cm ‒2 ( η10 = 76 mV) and an ultra-small Tafel slope of 46 mV∙dec ‒1 in 0.5 mol∙L ‒1 H 2SO 4. More importantly, the catalyst shows prominent high catalytic stability for HER (> 100 h). The acid-resistant MoO x wraps the inside Ni 3S 2/NF to ensure the high stability of the catalyst under acidic conditions. Density functional theory calculations confirm that the existing oxygen vacancy and MoO x/Ni 3S 2 heterostructure are both beneficial to the reduced Gibbs free energy of hydrogen adsorption (|∆ GH*|) over Mo sites, which act as main active sites. The heterostructure effectively decreases the formation energy of O vacancy, leading to surface reconstruction of the catalyst, further improving HER performance. The MoO x/Ni 3S 2/NF is promising to serve as a highly effective and durable electrocatalyst toward HER. 相似文献
9.
The role of a multifunctional catalyst for de-NO x process has been investigated. The NO x storage capacity of H 3PW 12O 40·6H 2O (HPW) was improved by the presence of a noble metal (Pt, Rh or Pd). Both HPW and noble metal were deposited on a specific support (based on Zr–Ce or Zr–Ti). The presence of noble metal in several oxidation states, as evidenced by TPR and IR, involves the possibility of forming different catalytic sites: (i) M 0 (zero-valent metal) and perhaps (ii) (metal–H) δ+ from specific interactions between noble metal and the HPW proton. Supports were also able to adsorb and activate NO x and to generate cationic catalytic sites (M x+). These cationic sites seem to be the clue for their important activity toward NO x reduction. This catalyst presents an outstanding resistance to SO 2 poisoning which can be related to NO and NO 2 absorption mechanism in HPW. The use of alternating short cycles of lean/rich mixtures allows us optimising the performance of this catalytic system in terms of both NO x reduction capacity and NO x storage efficiency: up to 48 and 84%, respectively (with a 2% CO + 1% H 2 mixture for reducing). Experimental results sustain two hypotheses: first, HPW-metal-support catalyst includes several (independent) catalytic functions required for a de-NO x process to occur and second, the formation of oxygenate active species must be indispensable for NO x reduction into nitrogen. 相似文献
10.
The study of the electrochemical behaviour of mixed spinel oxide electrodes, obtained by the partial replacement of Fe by Ni and/or Mn in the cobalt ferrite CoFe 2O 4 is presented. The electrodes were prepared by brush painting of iron substrates with a suspension of the respective oxide, prepared by solid-state reaction. The influence of the substituent on the electrodes electrocatalytic activity towards the OER is analysed in terms of the kinetic parameters obtained by steady state measurements and the cationic distribution proposed for the oxides. The data show that the introduction of Ni brings about the presence of Co 3+ tetrahedrally coordinated in addition to the Co 3+/Co 2+ couple in octahedral sites, giving rise to a better electrocatalyst for the OER. In contrast the presence of Mn produces electrodes with lower catalytic activity. 相似文献
11.
We present a density functional study on the mechanism of metal dusting at surfaces of transition metal oxides. The present study focuses on one of the major metal dusting processes: the Boudouard reaction on FeO(1 0 0) surface. Cluster models are used to represent the surface and the effects of cluster sizes and relaxation upon CO adsorption are carefully examined. It is found that the CO adsorption on a well-aligned transition metal oxide surface is very weak and does not lead to CO-bond dissociation. A minimum energy path of a gas-phase CO attacking an adsorbed CO from the surface normal is calculated and the structural change of the reaction species along the reaction path is examined. The results suggest that the Boudouard reaction is extremely unfavorable energetically at the transition metal oxide surfaces and that a pitting mechanism dictates the dusting process, in agreement with practical observations. 相似文献
12.
(MoVW) 5O 14-type oxides were identified as the active and selective components in industrial acrylic acid catalysts. Tungsten is suggested
to play an important role as a structural promoter in the formation and stabilization of this oxide. Vanadium is responsible
for high catalytic activities but is detrimental for the stability of this oxide at the necessary high concentrations for
optimum catalytic performance. The activity of mixed MoVW oxide catalysts for methanol, propene, and acrolein partial oxidation
could be considerably improved, when the amount of the (MoVW) 5O 14-type oxide was increased by thermal annealing. A model is proposed on the basis of the correlation between Raman wavenumber
and bond order and degree of reduction, which explains the observed different selectivities of MoO 3−x
and the (MoVW) 5O 14-type oxides in terms of metal–oxygen bond strengths, i.e. oxygen basicity and oxygen lability, respectively. According to
this model, the (MoVW) 5O 14 mixed oxide catalyses partial oxidation because of its intermediate C–H activation and oxygen releasing oxygen functionalities.
However, these (MoVW) 5O 14-type industrial oxidation catalysts are heterogeneous and highly complex systems. Their physicochemical characterization
also revealed that their chemical bulk and surface compositions vary with thermal activation and oxygen potential. A core-shell
model is suggested to describe the active catalyst state, the shell providing a high number of active centers, the core high
electronic conductivity and ion mobility. The fact that the surface composition of such catalysts is considerably different
from their bulk compositions, most probably implies that the “molecular structure” at their surface differs too considerably
from their bulk crystal structure. Hence, the posed question about the active catalyst structure and its relation to its catalytic
performance cannot unambiguously be explained by the crystallographic structure, but still remains unsolved. 相似文献
13.
The oriented structure of the exposed V=O bond of vanadium oxides on ZrO 2(100) was studied by in situ polarized total-reflection fluorescence X-ray absorption near-edge structure (XANES) spectroscopy. The pre-edge peak intensity of s-polarized XANES was half the intensity of the p-polarized one. Moreover, both pre-edge peaks decreased in a similar way and eventually became zero by the reaction of V=O bonds with NH 3 at 423 K, suggesting that all of the observed V=O bonds behaved as active sites. The present technique suggests that the exposed V=O bonds are oriented to a 45°-direction from the normal to the ZrO 2(100) surface. 相似文献
14.
Two new RESmTi 2O 7 mixed metal oxides were prepared by mixing Sm 2O 3, RE 2O 3 (RE = Gd, Er) and TiO 2 using a modified solid state method which gives the target pyrochlores with excellent phase purity. SmGdTi 2O 7 and SmErTi 2O 7 samples were characterized using PXRD, SEM, EDS, FT-IR and Raman spectroscopy. Rietveld refinement was employed to obtain crystallographic parameters using MAUD software. The qualitative phase analysis showed that the mixed metal oxides were crystallized in a cubic crystal system with the Fd3 m space group with small shifting in Bragg positions due to the effect of RE cationic radius on the lattice structure. The quantitative phase analysis using Rietveld refinement method illustrated the relation between crystallographic parameters, structural factors and ionic radii of RE atoms, during which, the sensitivity of the pyrochlores for cationic radius variations of RE atoms, and the extraordinary effect of the RE on the crystal structure of pyrochlores were confirmed. 相似文献
15.
Nanostructured VO 2(B) was synthesized via a combined hydrothermal method using V 2O 5 as a source material and oxalic acid powder as a reductant. Especially, cetyltrimethylammonium bromide (CTAB) was used as template and then three different morphologies of the VO 2(B): nanobelts, nanoflowers and nanoflakes were obtained through the change of the experimental conditions. The morphology and crystalline structure of the prepared products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the electrochemical charge–discharge cycling properties of the VO 2(B) nanostructures in lithium-ion battery were investigated. The results indicated that the belt-like, flower-like and flake-like VO 2(B) nanostructures have the initial specific discharge capacity of 205.2, 254.0 and 56.0 mA h g −1, and that the morphology of VO 2(B) nanostructures can deeply affect the service performance of batteries. According to the experiments, this CTAB-assisted hydrothermal method provides an insight into the preparation and application of nanostructured VO 2(B) as cathode material in lithium-ion battery. 相似文献
16.
This paper reports results of studies on structure and activity in soot combustion of nanocrystalline CeO 2 and CeLnOx mixed oxides (Ln = Pr, Tb, Lu, Ce/Ln atomic ratios 5/1). Nano-sized (4–5 nm) oxides with narrow size distribution were prepared by a microemulsion method W/O. Microstructure, morphology and reductivity of the oxides annealed up to 950 °C in O 2 and H 2 were analyzed by HRTEM, XRD, FT-IR, Raman spectroscopy and H 2-TPR. Obtained mixed oxides had fluorite structure of CeO 2 and all exhibited improved resistance against crystal growth in O 2, but only CeLuOx behaved better than CeO 2 in hydrogen. The catalytic activity of CeO2, CeLnOx and physical mixtures of CeO2 + Ln2O3 in a model soot oxidation by air was studied in “tight contact” mode by using thermogravimetry. Half oxidation temperature T1/2 for soot oxidation catalysed by nano-sized CeO2 and CeLnOx was similar and ca. 100 °C lower than non-catalysed oxidation. However, the mixed oxides were much more active during successive catalytic cycles, due to better resistance to sintering. Physical mixtures of nanooxides (CeO2 + Ln2O3) showed exceptionally high initial activity in soot oxidation (decrease in T1/2 by ca. 200 °C) but degraded strongly in successive oxidation cycles. The high initial activity was due to the synergetic effect of nitrate groups present in highly disordered surface of nanocrystalline Ln2O3 and enhanced reductivity of nanocrystalline CeO2. 相似文献
17.
Mixed oxides of general formulae Ta yNb 1−yO 5 (0< y<1) have been synthesized by a modified sol–gel method. Characterization of the samples has been carried out by x-ray diffraction, SEM/EDX, FTIR spectroscopy and thermal analysis. The electrochemical properties have been studied in a lithium cell. The first discharge capacity decrease from 206 ( y=0.25) to 136 mA h g −1 ( y=0.75). Ta yNb 1−yO 5 samples undergo an irreversible structural changes induced by electrochemical Li +-insertion. For all compositions, the new compounds formed after the first discharge has a very high cyclability, as shown the low capacity loss <1% per cycle. 相似文献
19.
Anhydrous α-alum materials doped with the trivalent samarium oxide Sm 2O 3 and denoted as KAl(SO 4) 2:xSm (x = 0; 0.5; 1; 1.5; 2; 2.5% mol.) are prepared by the solid-state reaction method at 350 °C. The resulting phases are crystallized in a simple hexagonal structure with space group P321. Powder X-ray diffraction (XRD), Infrared (IR), and Raman spectroscopies confirmed a high purity of phases with variation in lattice parameters according to the amount of doping.Optical measurements through absorption and fluorescence spectroscopies in the ultra-violet and visible regions prove the different electronic transitions between excited levels and 6H 5/2 ground state of Sm 3+, the incorporation of samarium in the crystal structure, and suggest the quenching phenomenon.The materials presented in the study showed an ionic semiconductor behavior with an increase in their conductivity as a function of the doping level. A 1D conduction is made according to the Correlated Barrier Hopping CBH model by cations mobility in crystalline sites under the effect of thermal agitation in the [170–250 °C] region. KAl(SO 4) 2: xSm (x = 1.5% mol.) with its lower activation energy value, is suggested as a suitable cathode material for aluminum-based batteries. 相似文献
20.
Electrocatalysts of the general formula Ir xRu 1−xO 2 were prepared using Adams’ fusion method. The crystallite characterization was examined via XRD, and the electrochemical properties were examined via cyclic voltammetry (CV) in, linear sweep voltammetry (LSV) and chronopotentiometry measurements in 0.5 M H 2SO 4. The electrocatalysts were applied to a membrane electrode assembly (MEA) and studied in situ in an electrolysis cell through electrochemical impedance spectroscopy (EIS) and stationary current density–potential relations were investigated. The Ir xRu 1−xO 2 ( x = 0.2, 0.4, 0.6) compounds were found to be more active than pure IrO 2 and more stable than pure RuO 2. The most active electrocatalyst obtained had a composition of Ir 0.2Ru 0.8O 2. With an Ir 0.2Ru 0.8O 2 anode, a 28.4% Pt/C cathode and the total noble metal loading of 1.7 mg cm −2, the potential of water electrolysis was 1.622 V at 1 A cm −2 and 80 °C. 相似文献
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