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1.
《Current Applied Physics》2018,18(4):417-423
We investigated synthesis and electrocatalytic performance of metal-free, nitrogen-doped carbon nano-onions (N-CNOs) for oxygen reduction reactions in alkaline electrolyte. N-CNOs were prepared by chemical oxidation of nanodiamond-derived carbon nano-onions (ox-CNOs), followed by thermal annealing with urea under the flow of argon gas. The chemical oxidation step was critical to successfully internalize nitrogen atoms into carbon network. Morphology, microstructure, and chemical states of carbon nano-onions (CNOs), ox-CNOs, and N-CNOs were characterized by transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Electrocatalytic activity of pristine and modified CNOs was characterized by a series of electrochemical measurements. Electrochemical characterizations were done with thin film electrodes of CNOs mounted on a glassy carbon disk. Compared to CNOs and ox-CNOs, N-CNOs showed remarkably enhanced electron-transfer kinetics with the 4-electron transfer as a dominant reaction pathway. Overall, N-CNOs exhibited electrochemical characteristics comparable to commercial Pt/C catalysts. 相似文献
2.
For the alkaline fuel cell cathode reaction, it is very essential to develop novel catalysts with superior catalytic properties. Here, we report the synthesis of highly active and stable MoS2/Pd composites for the oxygen reduction reaction (ORR), via a simple, eco-friendly sonochemical method. The bulk MoS2 was first transformed into single and few layers MoS2 nanosheets through ultrasonic exfoliation. Then the exfoliated MoS2 nanosheets served as supporting materials for the nucleation and further in-situ growth of Pd nanoparticles to form MoS2/Pd composites via ultrasonic irradiation. Cyclic voltammetry and rotating disk voltammetry measurements demonstrate that as-prepared MoS2/Pd composites which provides a direct four-electron pathway for the ORR, have better electrocatalytic activity, long-term operation stability than commercial Pt/C catalyst. We expect that the present work would provide a promising strategy for the development of efficient oxygen reduction electrocatalyst. In addition, this study can also be extended to the preparation of other hybrid with desirable morphologies and functions. 相似文献
3.
《Current Applied Physics》2015,15(12):1606-1614
B, N-codoped carbon nanofibers were massively prepared by heat treatment of electrospun carbon nanofibers with the mixture of boric acid/urea in N2 (BNCf-N) and subsequently activated in NH3 (BNCf-NA). The directly electrospun self-standing 3D non woven structure with void spaces between each fiber facilitates the mass transport of reactant and resulted molecules. Further NH3 activation gives BNCf-NA a high surface area of 306.3 m2 g−1 with micro/mesoporous structure, providing abundant passageway for proton transfer. Simultaneously, NH3 activation also realizes the optimization of surface functionalities, such as more B–N–C and pyridinic-N. These intriguing features render BNCf-NA excellent catalytic behavior with nearly four-electron oxygen reduction reaction (ORR) process in alkaline media, especially much better stability and methanol tolerance than the commercial Pt/C catalyst. Our work provides a large-scale preparation method for efficient metal-free catalysts toward ORR, thus further intensifying the commercial application of fuel cells. 相似文献
4.
In this study, carbon supported Pt and Pt-Pd were synthesized as oxygen reduction reaction electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs). Pt and Pt-Pd nanoparticles have been synthesized by reduction of metal precursors in presence of NaBH4. Various techniques such as X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were utilized to study the prepared samples. Furthermore, electrochemical properties of the prepared samples were evaluated from cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed, the crystallite size of electrocatalysts (Pt and Pt-Pd) is below 10 nm. The higher catalytic activity was detected for Pt-Pd/C electrocatalyst for oxygen reduction reaction (ORR). In addition, it is believed that the better performance of electrocatalyst is related to the synergic effect between Pt and Pd nanoparticles, weakening of the OO bond on Pd-modified Pt nanoparticles in ORR, uniform dispersion of Pd and Pt on the carbon support and higher electrochemical active surface area (EAS) of Pt-Pd/C electrocatalyst. 相似文献
5.
Co-doped flower-like SnS2 was synthesized using a one-step hydrothermal method. The Co content of Co-doped SnS2 was facilely tuned by controlling the [Co]/[Sn] molar concentration ratio (SC-x; x = 0.05, 0.5, 1.0 2.0, where x indicates the [Co]/[Sn] ratio). The morphology of the samples did not significantly change despite changes in the Co dopant content. Compared to SC-0 (667 mV), SC-0.05 (400 mV), SC-0.5 (382 mV), and SC-1.0 (374 mV), SC-2.0 showed higher catalytic performance, with an overpotential of 323 mV at a current density of 10 mA/cm2 in 1 M KOH solution. Moreover, SC-2.0 exhibited high stability for 12 h during chronopotentiometry. SC-2.0 was unexpectedly transformed to weakly crystallized CoOOH nanoparticles after the stability test. The transformation rate from Co-doped SnS2 to CoOOH was decreased with an increase in the Co content. 相似文献
6.
《Current Applied Physics》2015,15(9):993-999
Pt-transition metal alloy catalysts with an active Pt surface have exceptional properties for use in oxygen electro-reduction reactions in fuel cells. Herein, we report the simple synthesis of dealloyed PtCu catalysts and their catalytic performance in oxygen reduction. The dealloyed PtCu catalysts consisted of a Pt-enriched shell with a Pt–Cu alloy core and were synthesized through a chemical co-reduction process followed by thermal annealing and chemical dealloying. During synthesis, thermal annealing leads to a high degree of formation of PtCu alloy particles (e.g., PtCu or PtCu3), and chemical dealloying causes selective dissolution of unstable Cu species from the surface layers of the PtCu alloy particles, resulting in a PtCu alloy@Pt-enriched surface core–shell configuration. Our PtCu3/C catalyst exhibits a great improvement in the oxygen reduction reaction with a mass activity of 0.501 A/mgPt, which is 2.24 times greater than that of a commercial Pt catalyst. In this article, the synthesis details, characteristics and performance improvements in ORR of chemically dealloyed PtCu catalysts are systemically explained. 相似文献
7.
The inherent periodically arranged M−NX, M−SX and M−OX units (M are usually Fe, Co, Ni, etc.) in metal–organic frameworks (MOFs) can be promising active centers in electrocatalysis. In previous studies, MOFs were usually constructed by energy-consuming hydro- or solvo-thermal reactions. Ultrasonic synthesis is a rapid and environment-friendly technique when envisaging MOFs’ industrial applications. In addition, different synthetic pathways for MOFs may lead to difference in their microstructure, resulting in different electrocatalytic performance. Nevertheless, only a handful of MOFs were successfully prepared by ultrasonic synthesis and few were applied in electrochemical catalysis. Herein, we constructed Ni/Co-catecholates (Ni/Co-CATs) synthesized by one-step ultrasonic method (250 W, 40 KHz, 25 W/L, Ultrasonic clearing machine) and compared their performance in oxygen reduction reaction (ORR) with that of Ni/Co-CATs synthesized by hydrothermal method. Ni-CAT and Co-CAT prepared by ultrasonic showed the half-wave potential of −0.196 V and −0.116 V (vs. Ag/AgCl), respectively. The potentials were more positive than those prepared by hydro-thermal method. And they showed excellent electrochemical stability in neutral solution. The latter was only 32 mV lower than that of commercial Pt/C. The improved performance in ORR was attributed to higher specific surface area and mesopore volume as well as more structural defects generated in the ultrasonic synthesis process, which could facilitate their exposure of electrocatalytic active sites and their mass transport. This work gives some perspective into cost-effective synthetic strategies of efficient MOFs-based electrocatalysts. 相似文献
8.
Nowadays, the application of ultrasound (US) energy for assisting the lignocellulosic biomass and waste materials conversion into value-added products has dramatically increased. In this sense, this review covers theoretical aspects, promising applications, challenges and perspectives about US and its use for biomass treatment. The combination of US energy with a suitable reaction time, temperature and solvent contributes to the destruction of recalcitrant lignin structure, allowing the products to be used in thermochemical and biological process. The main mechanisms related to US propagation and impact on the fragmentation of lignocellulosic materials, selectivity, and yield of conversion treatments are discussed. Moreover, the synergistic effects between US and alternative green solvents with the perspective of industrial applications are investigated. The present survey analysed the last ten years of literature, studying challenges and perspectives of US application in biorefinery. We were aiming to highlight value-added products and some new areas of research. 相似文献
9.
The adsorption, diffusion and dissociation properties of O2 on the icosahedron (Ih) Ni@Pt12 core-shell nanoparticle were investigated using the ab initio density functional theory calculations. It is found that, compared with the Pt(111) surface, the Ih Ni@Pt12 core-shell nanoparticle can enhance the adsorption, diffusion and dissociation of O2, as well as the adsorption and diffusion of the atomic O (the dissociation product of O2), and therefore serve as a good catalyst for oxygen reduction reaction. Our study gives a reasonable theoretical explanation to the high catalytic activity of the Ni@Pt core-shell nanoparticles for the oxygen reduction reaction. 相似文献
10.
The development of cost-effective and active water-splitting electrocatalysts is an essential step toward the realization of sustainable energy. Its success requires an intensive improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. In this work, we designed a facile and one-route strategy to activate the surface of metallic nickel (Ni) for the OER in alkaline media by ultrasound (24 kHz, 44 W, 60% acoustic amplitude, ultrasonic horn). Sonoactivated Ni showed enhanced OER activity with a much lower potential at + 10 mA cm−2 of + 1.594 V vs. RHE after 30 min ultrasonic treatment compared to + 1.617 V vs. RHE before ultrasonication. In addition, lower charge transfer resistance of 11.1 Ω was observed for sonoactivated Ni as compared to 98.5 Ω for non-sonoactivated Ni. In our conditions, ultrasound did not greatly affect the electrochemical surface area (Aecsa) and Tafel slopes however, the enhancement of OER activity can be due to the formation of free OH• radicals resulting from cavitation bubbles collapsing at the electrode/electrolyte interface. 相似文献
11.
《Current Applied Physics》2020,20(3):456-461
Carbon-based electrocatalysts for oxygen reduction reaction (ORR), especially in anion exchange membrane fuel cells (AEMFCs), have received a lot of attention because they exhibit excellent stability and are comparable to commercial Pt/C catalysts. Currently, to maximize the catalytic activity of carbon-based electrocatalysts, there are two major strategies: heteroatom doping or exposing active edge sites. However, the approach of increasing heteroatomic dopants of active edge sites has been rarely addressed. In this study, we present a simple strategy to prepare edge-enriched graphene catalysts with an increased ratio of heteroatomic dopants suitable for ORR of AEMFCs. The catalysts were prepared under harsh oxidation conditions, followed by a simple co-doping process with boron and nitrogen. The ORR activity of the catalysts was observed to be related to an increase of edge sites with heteroatomic dopants. We believe that the edge-enriched structure leads to accelerated electron transfer with enhanced oxygen adsorption. 相似文献
12.
A persistent ultrasound-assisted hydrothermal method has been developed to prepare cobalt oxide incorporated nitrogen-doped graphene (Co3O4/N-GO) hybrids. The electrochemical behaviors and catalytic activity of the prepared hybrids have been systematically investigated as cathode materials for Al-air battery. The results show that ultrasonication can promote the yield ratio of Co3O4 from 63.1% to 70.6%. The prepared Co3O4/N-GO hybrid with ultrasonication exhibits better ORR activity over that without ultrasonication. The assembled Al-air battery using the ultrasonicated Co3O4/N-GO hybrid exhibited an average working voltage of 1.02 V in 4 M KOH electrolyte at 60 mA∙cm−2, approximately 60 mV higher than that using hybrid without ultrasonication. This should be attributed to large number density of fine Co3O4 particles growing on the dispersed GO sheets under the persistent ultrasonication. The related ultrasonic mechanism has been discussed in details. 相似文献
13.
ABSTRACT The development of high efficient cathode catalyst is known to be very important for the large-scale application of fuel cells. In this work, by using the density functional theory, metal-porphyrin (M?=?Mn, Co) carbon materials (Mn/CoN4-C) have been investigated as possible oxygen reduction reaction (ORR) catalysts. The calculated formation energies indicate that Mn/CoN4-C is stable thermodynamically. For MnN4-C, ORR proceeds with a four-electron process. While for CoN4-C, both two-electron pathway and four-electron pathway are competitive, with the former being slightly favoured. For both compounds, the O2 hydrogenation pathway is favoured compared with O2 dissociation pathway. In CoN4-C, the energy barrier is 0.13?eV for the two-electron pathway, while it is 0.47?eV for the four-electron pathway, much lower than 0.80?eV for pure Pt. These energy barriers are also much lower than that in MnN4-C, showing that CoN4-C has a better ORR activity than MnN4-C. The calculated working potential is 0.30?eV for CoN4 in the four-electron pathway. 相似文献
14.
Iridium oxide supported on Vulcan XC-72 carbon black (IrO2/C) as a cathode catalyst for polymer electrolyte fuel cell (PEFC) has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurement. The IrO2 particles were 8-160 nm in diameter. The oxygen electroreduction activity was studied by cyclic voltammetry (CV). It was found that IrO2/C had high oxygen reduction reaction (ORR) activity. The performance of the membrane electrode assemble (MEA) was also tested in a single PEFC and showed that IrO2/C catalyst would be potential candidates for use as cathode catalyst in PEFC. 相似文献
15.
The influence of ultrasound-assisted rapid hydrothermal synthesis of aluminosilicate ZSM-5 catalysts was examined in this work. A series of MFI-type nanostructured materials with sonochemical approach and conventional heating were synthesized and evaluated for conversion of methanol to propylene reaction. The prepared samples were tested by characterization analyses such as XRD, FESEM, BET-BJH, FTIR, TPD-NH3 and TG/DTG. The obtained results confirmed that ultrasound treatment enhanced the nucleation process and crystal growth for ZSM-5 sample synthesized at moderate temperature of 250 °C. Therefore, it was found the formation of pure MFI zeolite with high crystallinity and improved textural, structural and acidic properties for ZSM-5(UH-250) sample compared with the other zeolites. This observation was attributed to the relationship between the perfect crystallization mechanism and catalytic properties, which led to producing an efficient MFI zeolite toward the optimal catalytic performance. In this manner, the methanol conversion and products selectivity of prepared materials were carried out in MTP reaction at 460 °C and atmospheric pressure. The ZSM-5(UH-250) zeolite with slower deactivation regime exhibited the constant level of methanol conversion (84%) and high propylene selectivity (78%) after 2100 min time on stream. Moreover, the synthesis pathway for MFI zeolite at moderate temperature and also deactivation mechanism of improved sample were proposed. 相似文献
16.
In this work a new membrane electrode based on Pt-coated Nafion membrane was fabricated. Chemical deposition process was used to coat platinum on Nafion 117 membrane and then Pt-coated Nafion membrane was hot pressed on gas diffusion layer (GDL) to make new membrane electrode. The electrochemical and chemical studies of the Pt-coated Nafions were investigated by electrochemical techniques, X-ray diffraction and scanning electron microscopy. The electrochemical results indicated that as the concentration of H2PtCl6 increased, the oxygen reduction reaction rate increased until the concentration was reached where the reduction reaction was limited by the problem of mass transport. The electrochemical results for oxygen reduction reaction showed that the new electrode which prepared by plating Nafion membrane with 0.06 M H2PtCl6 in electroless plating solution, has a higher performance than other electrodes. The XRD results showed that the average platinum particle size of the best sample was about 3 nm. The loading of platinum for this electrode was 0.153 mg cm−2. 相似文献
17.
《Current Applied Physics》2015,15(6):727-732
Dioxygen adsorption and activation on metal-ligand systems are the key elements for biological oxidative metabolisms and also catalyst design for the oxygen reduction reaction (ORR). We show, through first-principles calculations, that similar dioxygen adducts can form on metal-free n-type doped hexagonal boron nitride (h-BN) nanostructures. The density of electron donors determines the charge state of dioxygen, either in superoxo and peroxo, which exactly correlates with the ‘end-on’ and ‘side-on’ configurations, respectively. Activated O2 in the superoxo state shows a better catalytic performance possibly mediating the direct four-electron reduction. The formation of hydrogen peroxide (H2O2) is practically eliminated, and thus we suggest that a surface coated with the n-type doped h-BN can be the basis for an ORR catalyst with increased stability. 相似文献
18.
Juan MaYawen Tang Gaixiu YangYu Chen Qun ZhouTianhong Lu Junwei Zheng 《Applied Surface Science》2011,257(15):6494-6497
The carbon supported PtP (PtP/C) catalysts were synthesized from Pt(NO3)2 and phosphorus yellow at the room temperature. The content of P in the PtP/C catalysts prepared with this method is high and the average size of the PtP particles is decreased with increasing the content of P. The electrocatalytic performances of the PtP/C catalysts prepared with this method for the oxygen reduction reaction (ORR) are better than that of the commercial Pt/C catalyst. The promotion action of P for enhancing the electrocatalytic performance of the PtP/C catalyst for ORR is mainly due to that Pt and P form the alloy and then the electron density of Pt is decreased. 相似文献
19.
Bifunctional electrocatalysts to enable efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for fabricating high performance metal–air batteries and fuel cells. Here, a defect rich nitrogen and sulfur co-doped graphene/iron carbide (NS-GR/Fe3C) nanocomposite as an electrocatalyst for ORR and OER is demonstrated. An ink of NS-GR/Fe3C is developed by homogeneously dispersing the catalyst in a Nafion containing solvent mixture using an ultrasonication bath (Model-DC150H; power − 150 W; frequency − 40 kHz). The ultrasonically prepared ink is used for preparing the electrode for electrochemical studies. In the case of ORR, the positive half-wave potential displayed by NS-GR/Fe3C is 0.859 V (vs. RHE) and for the OER, onset potential is 1.489 V (vs. RHE) with enhanced current density. The optimized NS–GR/Fe3C electrode exhibited excellent ORR/OER bifunctional activities, high methanol tolerance and excellent long-term cycling stability in an alkaline medium. The observed onset potential for NS–GR/Fe3C electrocatalyst is comparable with the commercial noble metal catalyst, thereby revealing one of the best low-cost alternative air–cathode catalysts for the energy conversion and storage application. 相似文献
20.
There are many problems associated with the synthesis of nanocatalysts and catalytic reduction of nitroarenes - e.g., high temperatures, costs, long reaction/synthesis process times, the toxicity of chemicals/solvents, undesirable byproducts, the toxic/harmful wastes, low efficiency/selectivity, etc. This study represents an attempt to overcome these challenges. To this purpose, biocompatible and highly efficient Ag2Se quantum dots (QDs) catalysts with antibacterial activity were synthesized in a very rapid (30 sec, rt), simple, inexpensive, sustainable/green, and one-pot strategy in water using ultrasonic irradiation. Characterization of the QDs was performed using different techniques. UV–Vis absorption and fluorescence spectroscopic studies showed an absorption peak at 480–550 nm and a maximum emission peak around 675 nm, which confirmed the successful synthesis of Ag2Se QDs via the applied biosynthetic method. Subsequently, catalytic reduction of nitroarenes by them was carried out under safe conditions (H2O, rt, air atmosphere) in ∼ 60 min with excellent yield and selectivity (>99%). Their catalytic activity in the reduction of various toxic nitroarenes to aminoarenes under green conditions was investigated. Thus, a rapid and safe ultrasound-based method was employed to prepare stable and green Ag2Se QDs phyto-catalysts with unique properties, including exquisite monodispersity in shape (orthorhombic) and size (∼7 nm), air-stability, and good purity and crystallinity. Importantly, instead of various toxic chemicals, the plant extract obtained by rapid ultrasonic method (10 min, rt) was used as natural reducing, capping, and stabilizing agents. Moreover, antibacterial assays results showed that Ag2Se-QDs catalysts at low concentrations (ppm) have high activity against all tested bacteria, especially E. coli (MIC:31.25 ppm, MBC:125 ppm) which were significantly different from those of Fig extract (MIC = MBC:500 ppm). The data reflect the role of these bio-synthesized Ag2Se-QDs catalysts in the development of versatile and very safe catalysts with biomedical properties. 相似文献