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1.
Heterostructured Mo2C-MoOx on carbon cloth (Mo2C-MoOx/CC), as a model of easily oxidized electrocatalysts under ambient conditions, is investigated to uncover surface reconfiguration during the hydrogen evolution reaction (HER). Raman spectroscopy combined with electrochemical tests demonstrates that the MoVI oxides on the surface are in situ reduced to MoIV, accomplishing promoted HER in acidic condition. As indicated by density functional theoretical calculations, the in situ reduced surface with terminal Mo=O moieties can effectively bring the negative ΔGH* on bare Mo2C close to a thermodynamic neutral value, addressing difficult H* desorption toward fast HER kinetics. The optimized Mo2C-MoOx/CC only requires a low overpotential (η10) of 60 mV at −10 mA cm−2 in 1.0 m HClO4, outperforming Mo2C/CC and most non-precious electrocatalysts. In situ surface reconfiguration are shown on W2C-WOx, highlighting the significance to boost various metal-carbides and to identify active sites.  相似文献   

2.
As promising supports, reducible metal oxides afford strong metal–support interactions to achieve efficient catalysis, which relies on their band states and surface stoichiometry. In this study, in situ and controlled hydrogen doping (H doping) by means of H2 spillover was employed to engineer the metal–support interactions in hydrogenated MoOx‐supported Ir (Ir/H?MoOx) catalysts and thus promote furfural hydrogenation to furfuryl alcohol. By easily varying the reduction temperature, the resulting H doping in a controlled manner tailors low‐valence Mo species (Mo5+ and Mo4+) on H?MoOx supports, thereby promoting charge redistribution on Ir and H?MoOx interfaces. This further leads to clear differences in H2 chemisorption on Ir, which illustrates its potential for catalytic hydrogenation. As expected, the optimal Ir/H?MoOx with controlled H doping afforded high activity (turnover frequency: 4.62 min?1) and selectivity (>99 %) in furfural hydrogenation under mild conditions (T=30 °C, P =2 MPa), which means it performs among the best of current catalysts.  相似文献   

3.
Molybdenum carbide (Mo2C) is a promising noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER), due to its structural and electronic merits, such as high conductivity, metallic band states and wide pH applicability. Here, a simple CVD process was developed for synthesis of a Mo2C on carbon cloth (Mo2C@CC) electrode with carbon cloth as carbon source and MoO3 as the Mo precursor. XRD, Raman, XPS and SEM results of Mo2C@CC with different amounts of MoO3 and growth temperatures suggested a two-step synthetic mechanism, and porous Mo2C nanostructures were obtained on carbon cloth with 50 mg MoO3 at 850 °C (Mo2C-850(50)). With the merits of unique porous nanostructures, a low overpotential of 72 mV at current density of 10 mA cm−2 and a small Tafel slope of 52.8 mV dec−1 was achieved for Mo2C-850(50) in 1.0 m KOH. The dual role of carbon cloth as electrode and carbon source resulted into intimate adhesion of Mo2C on carbon cloth, offering fast electron transfer at the interface. Cyclic voltammetry measurements for 5000 cycles revealed that Mo2C@CC had excellent electrochemical stability. This work provides a novel strategy for synthesizing Mo2C and other efficient carbide electrocatalysts for HER and other applications, such as supercapacitors and lithium-ion batteries.  相似文献   

4.
将超小Ru纳米团簇锚定于富含氧空位MoO3-x纳米带的双功能催化剂(Ru/MoO3-x)。该催化剂展现出优异的肼氧化(HzOR)和析氢反应(HER)催化性能,10 mA·cm-2时的过电势分别为-79和-27 mV,所组成的肼辅助电催化全解水(OWS)的电解池电压仅为13 mV,明显优于商业化20% Pt/C和已报道的一些催化剂。如此优异的性能主要归因于Ru纳米团簇有利于HzOR中N2H4的脱氢和HER氢中间体的吸/脱附平衡以及MoO3-x中的氧空位和Ru/MoO3-x异质结构导致的丰富的电化学活性位点和优化的电子转移动力学。  相似文献   

5.
《化学:亚洲杂志》2017,12(4):446-452
Here we report a redox‐anchoring strategy for synthesizing a non‐noble metal carbide (MoCx) nanocomposite electrocatalyst for water electrolysis in acidic media, using glucose and ammonium heptamolybdate as carbon and Mo precursors, respectively, without the need of gaseous carbon sources such as CH4. Specifically, the aldehyde groups of glucose are capable of reducing Mo6+ to Mo4+ (MoO2), and thus molybdenum species can be well anchored by a redox reaction onto a carbon matrix to prevent the aggregation of MoCx nanoparticles during the following carbonization process. The morphology and chemical composition of the electrocatalysts were well characterized by BSE‐SEM, TEM, XRD and XPS. The obtained MoCx−2 sample showed a reasonably high hydrogen evolution reaction (HER) activity and excellent stability in an acidic electrolyte, and its overpotential required for a current density output of 20 mA cm−2 is as low as 193 mV. Such a prominent performance is ascribed to the excellent dispersity and nano‐size, and the large reactive surface area of MoCx particles. This work may open a new way to the design and fabrication of other non‐noble metal carbide nanocatalysts for various electrochemical applications.  相似文献   

6.
The replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of ?6 mV, a small Tafel slope of 41 mV dec?1, and a large exchange current density of 0.179 mA cm?2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER.  相似文献   

7.
Developing highly efficient, cost-saving, and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) continues to be a significant challenge in the energy field. In this work, we decide to prepare an unusual multifunctional electrocatalyst, such as icosahedral palladium nanocrystals (PdNCs) encapsulating on N–MoO2–Mo2C half-hollow nanotube (HHNT) heterointerface, using an in-situ chemical reaction and following sonic probe irradiation method. All the experiments demonstrate that special defect-enriched heterointerfaces N–MoO2–Mo2C supported Pd nanocomposite can greatly improve the ORR activity (Eonset = 1.01 V and E1/2 = 0.90 V) with good stability, outstanding HER (η10 = 65 mV) and OER (η10 = 180 mV) performances than those of commercial precious electrocatalysts (Platinum on carbon [Pt/C] and ruthenium oxide [RuO2]). The overall water splitting electrolyzer fabricates by Pd/N–MoO2–Mo2C as both anode and cathode electrodes to achieve a current density of 10 Ma/cm2 at a cell voltage of 1.56 V, which surpasses the most recent reported electrocatalysts.  相似文献   

8.
A straightforward aqueous synthesis of MoO3?x nanoparticles at room temperature was developed by using (NH4)6Mo7O24?4 H2O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as‐prepared products are nanoparticles with diameters of 90–180 nm. The diffuse reflectance UV‐visible‐near‐IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible‐light and near‐infrared region, such nanostructures exhibit an enhancement of activity toward visible‐light catalytic hydrogen generation. MoO3?x nanoparticles synthesized with a molar ratio of MoVI/MoV 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as‐prepared plasmonic MoO3?x nanoparticles, which reveals its potential application in visible‐light catalytic hydrogen production.  相似文献   

9.
The advantages of hydrogen evolution reaction (HER) in strongly buffered neutral pH are manifold including enhanced stability of the electrocatalysts, oxygen tolerance, safer and environmental friendly devices, etc., yet, not much research effort has been devoted on the subject. HER activities of several low-cost electrocatalysts like Mo2C, MoS2, CoSe2 and NiSe2 have been studied in sodium phosphate buffer solution of pH 5. An optimal buffer concentration of 1.75 M was observed for the electrocatalysts. Compared to un-buffered electrolyte, a reduction of about 100 mV in the onset overpotential has been achieved. The electrocatalysts are highly oxygen tolerant with more than 90% HER selectivities. Furthermore, electrochemical surface area of Mo2C was evaluated by capacitance and surface oxidation methods to obtain an insight on the specific adsorption of buffer electrolytes.  相似文献   

10.
With the environmental pollution and non‐renewable fossil fuels, it is imperative to develop eco‐friendly, renewable, and highly efficient electrocatalysts for sustainable energy. Herein, a simple electrospinning process used to synthesis Mo2C‐embedded multichannel hollow carbon nanofibers (Mo2C‐MCNFs) and followed by the pyrolysis process. As prepared lotus root‐like nanoarchitecture could offer rich porosity and facilitate the electrolyte infiltration, the Mo2C‐MCNFs delivered favourable catalytic activity for HER and OER. The resultant catalysts exhibit low overpotentials of 114 mV and 320 mV at a current density of 10 mA cm?2 for HER and OER, respectively. Furthermore, using the Mo2C‐MCNFs catalysts as a bifunctional electrode toward overall water splitting, which only needs a small cell voltage of 1.68 V to afford a current density of 10 mA cm?2 in the home‐made alkaline electrolyzer. This interesting work presents a simple and effective strategy to further fabricating tunable nanostructures for energy‐related applications.  相似文献   

11.
A novel in situ N and low‐valence‐state Mo dual doping strategy was employed to significantly improve the conductivity, active‐site accessibility, and electrochemical stability of MoO3, drastically boosting its electrochemical properties. Consequently, our optimized N‐MoO3?x nanowires exhibited exceptional performances as a bifunctional anode material for both fiber‐shaped asymmetric supercapacitors (ASCs) and microbial fuel cells (MFCs). The flexible fiber‐shaped ASC and MFC device based on the N‐MoO3?x anode could deliver an unprecedentedly high energy density of 2.29 mWh cm?3 and a remarkable power density of 0.76 μW cm?1, respectively. Such a bifunctional fiber‐shaped N‐MoO3?x electrode opens the way to integrate the electricity generation and storage for self‐powered sources.  相似文献   

12.
Vanadium‐containing heteropoly acid solutions of Keggin H3+xPMo12–xVxO40 and modified HaPzMoyVxOb types (P‐Mo‐V HPAs) are promising nanosized inorganic metal‐oxygen cluster compounds with the property of reversible oxidability (VV ↔ VIV). The oxidation of reduced P‐Mo‐V HPAs at a temperature of 130–170 °C and an oxygen pressure of 4 atm is a convenient method for their regeneration, but results in regeneration degree of only 75–88 %. Various materials with electron transfer or oxidative properties, such as nitrogen doped carbon nanofibers (N‐CNFs), Sibunit‐4, HNO3, and MoO2, were investigated as additives to facilitate and accelerate the regeneration of HPA solutions. Among the studied additives HNO3 was found to show the best efficiency, resulting in regeneration degree of higher 95 %. Rapid and efficient regeneration of spent HPA catalysts is an important criterion for achieving high productivity and sustainability of oxidative processes on their basis.  相似文献   

13.
In our efforts to obtain electrocatalysts with improved activity for water splitting, meticulous design and synthesis of the active sites of the electrocatalysts and deciphering how exactly they catalyze the reaction are vitally necessary. Herein, we report a one‐step facile synthesis of a novel precious‐metal‐free hydrogen‐evolution nanoelectrocatalyst, dubbed Mo2C@NC that is composed of ultrasmall molybdenum carbide (Mo2C) nanoparticles embedded within nitrogen‐rich carbon (NC) nanolayers. The Mo2C@NC hybrid nanoelectrocatalyst shows remarkable catalytic activity, has great durability, and gives about 100 % Faradaic yield toward the hydrogen‐evolution reaction (HER) over a wide pH range (pH 0–14). Theoretical calculations show that the Mo2C and N dopants in the material synergistically co‐activate adjacent C atoms on the carbon nanolayers, creating superactive nonmetallic catalytic sites for HER that are more active than those in the constituents.  相似文献   

14.
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16.
Transition metal phosphide is regarded as one of the most promising candidates to replace noble-metal hydrogen evolution reaction (HER) electrocatalysts. Nevertheless, the controllable design and synthesis of transition metal phosphide electrocatalysts with efficient and stable electrochemical performance are still very challenging. Herein, a novel hierarchical HER electrocatalyst consisting of three-dimensional (3D) coral-like Mn-doped Co2P@an intermediate layer of Ni2P generated in situ by phosphorization on Ni foam (MnCoP/NiP/NF) is reported. Notably, both the incorporation of Mn and introduction of the Ni2P interlayer promote Co atoms to carry more electrons, which is beneficial to reduce the force of the Co−H bond and optimize the adsorption energy of hydrogen intermediate (|ΔGH*|), thereby making MnCoP/NiP/NF exhibit outstanding HER performance with onset overpotential and Tafel slope as low as 31.2 mV and 61 mV dec−1, respectively, in 1 m KOH electrolyte.  相似文献   

17.
Developing highly active, stable and robust electrocatalysts based on earth‐abundant elements for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is important for many renewable energy conversion processes. Herein, NixCo3‐xO4 nanoneedle arrays grown on 3D porous nickel foam (NF) was synthesized as a bifunctional electrocatalyst with OER and HER activity for full water splitting. Benefiting from the advantageous structure, the composite exhibits superior OER activity with an overpotential of 320 mV achieving the current density of 10 mA cm?2. An exceptional HER activity is also acquired with an overpotential of 170 mV at the current density of 10 mA cm?2. Furthermore, the catalyst also shows the superior activity and stability for 20 h when used in the overall water splitting cell. Thus, the hierarchical 3D structure composed of the 1D nanoneedle structure in NixCo3‐xO4/NF represents an avenue to design and develop highly active and bifunctional electrocatalysts for promising energy conversion.  相似文献   

18.
采用水热法合成了MoO_3/酚醛树脂前驱体,然后在空气中进行煅烧处理,成功制备了一种新型核壳MoOx/C微球。对材料的晶体结构、形貌和元素价态进行分析表明,该材料的主要成分是单斜相MoO_2、正交晶系MoO_3和碳。树脂在空气中的煅烧碳化将MoO_3/酚醛树脂前驱体中的六方晶系的MoO_3还原为单斜相MoO_2。其中少量的MoO_2会在空气中重新被氧化成正交晶系的MoO_3,形成了MoO_2/MoO_3异质结构。在这一系列反应的综合作用下,形成这种表面有裂纹的核壳MoOx/C微球复合材料。将该材料用作锂离子电池负极材料,表现出了循环稳定性高、倍率性能好等优异的电化学性能。在100 mA·g-1的电流密度下充放电循环100次之后,可逆容量达640.6 mAh·g-1。  相似文献   

19.
The title compound, {(C12H13N2)2[Mo5O16]}n, was synthesized under hydro­thermal conditions. The structure contains a two‐dimensional layer, constructed from [(Mo4O14)n]4n chains linked through MoO6 octahedra, which lie across twofold axes. The [(Mo4O14)n]4n chain consists of [Mo4O14]4− clusters connected to one another by sharing their MoO5 square‐pyramidal and MoO6 octahedral vertices in an anti disposition. The layers are linked by the cation, to which they are connected via N—H⋯O hydrogen bonds.  相似文献   

20.
We report an oxygen vacancy (Vo)-rich metallic MoO2−x nano-sea-urchin with partially occupied band, which exhibits super CO2 (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The Vo-rich MoO2−x nano-sea-urchin displays a CH4 evolution rate of 12.2 and 5.8 μmol gcatalyst−1 h−1 under full spectrum and NIR light illumination in concentrated CO2, which is ca. 7- and 10-fold higher than the Vo-poor MoO2−x, respectively. More interestingly, the as-developed Vo-rich MoO2−x nano-sea-urchin can even reduce CO2 directly from the air with a CO evolution rate of 6.5 μmol gcatalyst−1 h−1 under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO2−x can facilitate CO2 adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH4 because of the formation of a highly stable Mo−C−O−Mo intermediate.  相似文献   

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