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1.
A class of ruthenium-nickel alloy catalysts featured with nanoporous nanowires (NPNWs) were synthesized by a strategy combining rapid solidification with two-step dealloying. RuNi NPNWs exhibit excellent electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in which the RuNi-2500 NPNWs catalyst shows an OER overpotential of 327 mV to deliver a current density of 10 mA cm?2 and the RuNi-0 NPNWs catalyst requires the overpotential of 69 mV at 10 mA cm?2 showing the best HER activity in alkaline media. Moreover, the RuNi-1500 NPNWs catalyst was used as the bifunctional electrocatalyst in a two-electrode alkaline electrolyzer for water splitting, which exhibits a low cell voltage of 1.553 V and a long-term stability of 24 h at 10 mA cm?2, demonstrating that the RuNi NPNWs catalysts can be considered as promising bifunctional alkaline electrocatalysts.  相似文献   

2.
Pd/xCuO–10CNT (x = 1, 2, 3, 4) catalysts were synthesized using an improved polyol method. Uniformly prepared catalyst structures and chemical compositions of the catalysts delivered a high oxidation performance. The prepared catalysts were characterized via transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The formation of homogenous active Pd metal and CuO nanoparticle-modified CNT surfaces was found. Meanwhile, the electrocatalytic activity and the long-term stability performance of the prepared catalysts toward formic acid oxidation reaction (FAOR) were also employed via cyclic voltammogram (CV) and chronoamperometry (CA), respectively. Prominently, the prepared Pd/xCuO–CNT nanocomposite catalyst presented an outstanding electrocatalytic performance with a higher maximum forward peak current density (26.9 mA cm?2) than those of catalysts Pd/CNT (3.4 mA cm?2) and Pd/C (2.3 mA cm?2) toward FAOR in the H2SO4 electrolyte, representing high conductivity CNT, and dispersed Pd nanoparticles with a large active surface area, on the CuO-CNT support. Additionally, the prepared catalysts also had outstanding stability and an excellent CO poisoning tolerance through the modified Pd structures on CuO-supported CNT. The insertion of CuO onto the CNT surface before Pd loading provided additional electrochemical active sites due to the enhanced geometric and bifunctional system. CuO supports the adsorption of oxygen-containing species (OHads) on the catalyst surface, and the electron effect among Pd and Cu metals is beneficial for charge transfer.  相似文献   

3.
In this work, PdO/TiO2 and Eu2O3/TiO2 nanocomposites (NCs) were synthesized using a new facile, template‐free, and one‐step solvothermal approach and characterized by several instrumentation techniques. X‐ray photoelectron spectroscopy studies revealed the presence of oxidized form of the Pd and Eu nanoparticles within the NC materials (PdO and Eu2O3). The two catalysts exhibited remarkable activity for the hydrogen evaluation reaction (HER) in a strong alkaline solution (4.0 M NaOH) with PdO/TiO2 catalyst being the best, which recorded an exchange current density (jo) of 0.26 mA cm?2 and a Tafel slope (βc) of 125 mV dec?1. Such parameters are not far from those recorded for a commercial Pt/C catalyst (0.71 mA cm?2 and 120 mV dec?1) performed here under the same operating conditions. Eu2O3/TiO2 catalyst recorded jo and βc values of 0.05 mA cm?2 and 135 mV dec?1. The Tafel slopes 125 and 135 mV dec?1 calculated on the PdO/TiO2 and Eu2O3/TiO2 catalysts suggest a HER kinetics controlled by the Volmer step. PdO/TiO2 catalyzed the HER with a high turnover frequency of 2.3 H2/s at 0.2 V versus the reversible hydrogen electrode, while Eu2O3/TiO2 catalyst only measured a turnover frequency value of 1.25 H2/s at the same overpotential. The two catalysts exhibited excellent stability and durability after 10 000 cycles and 72 hours of controlled potential electrolysis at a high cathodic overpotential, reflecting their practical applicability. Scanning electron microscope and X‐ray photoelectron spectroscopy examinations revealed that the morphology and chemistry of both catalysts were not altered as a result of the performed long‐term stability and durability tests.  相似文献   

4.
It is very important to develop hydrogen evolution catalyst with high activity and low cost to solve energy crisis. The abundant non-precious metals and phosphides have attracted much attention and are expected to replace platinum catalysts. Herein, we report an approach to prepare nest-like porous MnCo–P electrocatalyst on the nickel foam by two-step electrodeposition. The prepared bimetallic phosphide MnCo–P3/NF has excellent hydrogen catalytic activity. In the 1 M NaOH solution, the current density of 10 mA cm?2 required overpotential is only 47 mV, its Tafel slope is 56.4 mV dec?1, and the higher current density 100 mA cm?2 required overpotential is only 112 mV. More importantly, the MnCo–P3/NF catalyst has a long-term stability of electrocatalytic hydrogen evolution. After 24 h catalytic hydrogen evolution test at a constant current density of 20 mA cm?2, its potential basically does not change. Furthermore, the current density only changes slightly after 1500 cycles of CV test. All these well prove that the prepared MnCo–P3/NF catalyst has a long-term hydrogen evolution stability. According to performance testing and morphological characterization, the MnCo–P3/NF has a high hydrogen catalytic activity and stability are due to its larger active area, lower interface charge transfer resistance and stronger mechanical stability. In summary, the study explores a method of preparing bimetallic phosphides as an efficient and stable hydrogen evolution catalyst.  相似文献   

5.
An ongoing challenge still lies in the exploration of proficient electrocatalysts from earth-abundant non-precious metals instead of noble metal-based catalysts for clean hydrogen energy through large-Scale electrochemical water splitting. However, developing a non-precious transition metals based, stable electrocatalyst for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) is important challenge for modern energy conversion technology. In this report Vanadium doped bimetallic nickel-iron nanoarray, fabricated by carbon supported architecture through carbonization process for electrochemical water splitting. Three types of catalysts were prepared in different molar ratio of Ni/Fe. The electrocatalytic performance demonstrated that the catalyst with equal mole ratio (0.06:0.06) of Ni/Fe possess high catalytic activity for both OER and HER in alkaline and acidic medium. Besides, our findings revealed that the doping of vanadium could play a strong synergetic effect with Ni/Fe, which provide a small overpotential of 90 mV and 210 mV at 10 mA cm?2 for HER and OER respectively compared to the other two catalyst counterparts. Also, the catalyst with 1:1 (Ni/Fe) molar ratio showed a high current density of 208 mA cm?2 for HER at 0.5 M H2SO4 and 579 mA cm?2 for OER at 1 M KOH solution, the both current densities are much higher than the other two catalysts (different Ni/Fe ratio). In addition, the presented catalysts showed extremely good durability, reflecting in more than 20 h of consistent Chronoamprometry study at fixed overpotential η = 250 mV without any visible voltage elevation. Similarly, the (Ni/Fe) equal ratio catalyst showed better corrosion potential 0.209 V vs Ag/AgCl and lower current density 0.594 × 10?12 A cm?2 in high alkaline medium. The V-doping, MOF/GO surface defects are significantly increased the corrosion potential of the V-NixFey-MOF/GO electrocatalyst. Besides, the water electrolyzed products were analysed by gas chromatography to get clear insights on the formed H2 and O2 products.  相似文献   

6.
The transition metal phosphates are earth-abundant minerals that have been shown to perform well in electrocatalytic water splitting, whereas these catalysts still tend to have excessively high overpotentials and slow kinetics in HER and OER processes. In the present work, hybrid catalysts consisting of Pt quantum dots doped NiP (NiP-Pt) nano-embroidery spheres and Co(OH)2 nanosheets were successfully prepared by two-step electrodeposition method. The excellent catalytic performance of the catalyst relies principally on the synergistic interaction between NiP and Pt quantum dots. Additionally, the NiP-Pt exhibits strong electronic interactions at the interface with Co(OH)2. Consequently, the catalyst has a strong catalytic performance in terms of HER and OER catalytic performance. In terms of HER, an overpotential of only 40 mV is required when the current density reaches 10 mA cm?2, corresponding to a Tafel slope of 49.85 mV·dec?1. At the same time, the catalyst also performs well at OER, with a current density of 10 mA cm?2 at an overpotential of 186 mV and a Tafel slope of 53.049 mV·dec?1 much less than most electrocatalysts. This study involving electrodeposition and doping of quantum dots provides a new idea for the efficient synthesis of fundamental HER and OER bifunctional catalysts.  相似文献   

7.
Reduced graphene oxide (RGO) is used in many energy applications, especially in Polymer Electrolyte Membrane (PEM) fuel cells, as carbon sourced catalyst support materials. In this study, thermally (T-RGO) and chemically (C-RGO) reduced GO support materials were synthesized for utilization in PEM fuel cells. Pt catalysts were synthesized using supercritical carbon dioxide (SCCO2) deposition technique over synthesized support materials. Physical (BET, SEM-EDX, FTIR, RAMAN, XRD, TEM, ICP-MS and optical tensiometer) and electrochemical (CV, PEM fuel cell test) characterizations of synthesized support materials and corresponding Pt catalysts were performed. The differences between the structures of thermally and chemically reduced graphene oxide supports and their Pt catalysts were investigated. The ECSA values of the Pt/T-RGO and Pt/C-RGO catalysts are 19.86 m2 g?1 and 6.31 m2 g?1, respectively. The current and power density values of the Pt/T-RGO and Pt/C-RGO catalysts at 0.6 V are 84 mA cm?2, 80 mA cm?2 and 50 mW cm?2, 45 mW cm?2, respectively. Pt/T-RGO and Pt/C-RGO catalysts showed similar trend in PEMFC environment.  相似文献   

8.
The design of high-performance non-noble-metal-based electrocatalysts for electrooxidation reactions involving splitting of water molecule for energy and environmental applications is the need of the hour. In this study, we report the electrocatalytic performance of a nanocomposite catalyst of FeNi2S4 nanoparticles/CoFe nanowires supported on nickel foam that was prepared by a simple hydrothermal method. The electrocatalyst has several advantages, such as the nanocomposite structure, relatively high electrical conductivity, and synergistic effect between FeNi2S4 and CoFe. These characteristics enhanced the catalytic efficiency of FeNi2S4/CoFe electrode, gaining small overpotentials of 380 and 207 mV for oxygen and hydrogen evolution reactions, respectively, at a current density of 100 mA cm?2. The charge transfer processes are significantly improved by the electron pairs from FeNi2S4 and CoFe, as well as by the enhanced active sites at the electrode-electrolyte interface and their bonding interactions. The electrooxidation of urea was also explored, which showed a lower overpotential of 230 mV to reach 100 mA cm?2 current density. Interestingly, FeNi2S4/CoFe was successfully employed as cathode and anode for urea-assisted water electrolysis, utilizing 1.56 V to produce 10 mA cm?2 current density, which is approximately 160 mV below that for water electrolysis, thus verifying the lower energy consumption during electrolysis. These results indicate that nanoparticle and nanowire composite catalysts can be used for wastewater treatment and green energy production applications.  相似文献   

9.
EOR is a semi-reaction of direct ethanol fuel cells (DEFCs), and determines the performance of the DEFCs. Therefore, it is very important for EOR to rationally design an electrocatalyst with excellent activity, stability and CO-resistance. Based on this, we report the synthesis of MOF based composite catalysts by a facile method, which is formed by combining polyaniline hydrogel (PANH) with MOF 1 and carbon cloth (CC). At the same time, the structures of the composites were characterized by XRD, SEM and XPS. Under the optimum conditions, the j value for EOR is 107 mA cm?2 under alkaline conditions at 0.6 V, which indicates that composite 2 has excellent catalytic activity for EOR, and is superior to that of the previously reported nickel-based catalysts for EOR. The Tafel slope and the exchange current density of composite 2 are 88.9 mV dec?1 and 1.95 × 10?5 A cm?2 respectively. In addition, the j value of composite 2 was 65% of the original value after 1000 CV cycles. However, when the electrolyte was changed into the original one (1 M KOH + 1 M EtOH), the j value returned to 74% of the original value. Based on the excellent electrocatalytic performance, good stability and anti-CO poisoning, composite 2 is expected to be an economic, efficient and CO poisoning resistant electrocatalyst for EOR.  相似文献   

10.
Transition metal compounds, especially layered double hydroxide materials (LDHs), show excellent catalytic activity in oxygen evolution reaction (OER). The ethanol oxidation reaction (EOR) is an innovative alternative anodic reaction to OER for improving the efficiency of water splitting to produce hydrogen. In order to improve the reactivity and explore the similarities and differences of active sites in the two reactions, three kinds of porous LDHs (NiFe, NiCo, CoFe LDHs) were synthesized and a series of tests were carried out. Among them, the best performing OER catalyst is NiFe-LDHs with a low overpotential of 1.44 V vs. RHE at 10 mA cm?2 and a Tafel slope of 23.85 mV dec?1. As for the EOR reaction, NiCo-LDHs is the best, with an overpotential of only 1.38 V vs. RHE at 10 mA cm?2 and a Tafel slope of 71.58 mV dec-1. In addition, compared with OER, the LHDs material exhibited better stability in the EOR. This work provides a new direction for studying the electrocatalytic activity of LDHs materials in OER and EOR.  相似文献   

11.
The rational design of catalysts with low cost, high efficient and robust stability toward oxygen evolution reaction (OER) is greatly desired but remains a formidable challenge. In this work, a one-pot, spatially confined strategy was reported to fabricate ultrathin NiFe layered double hydroxide (NiFe-LDH) nanosheets interconnected by ultrafine, strong carbon nanofibers (CNFs) network. The as-fabricated NiFe-LDH/CNFs catalyst exhibits enhanced OER catalytic activity in terms of low overpotential of 230 mV to obtain an OER current density of 10 mA cm?2 and very small Tafel slope of 34 mV dec?1, outperforming pure NiFe-LDH nanosheets assembly, commercial RuO2, and most non-noble metal catalysts ever reported. It also delivers an excellent structural and electrocatalytic stability upon the long-term OER operation at a large current of 30 mA cm?2 for 40 h. Furthermore, the cell assembled by using NiFe-LDH/CNFs and commercial Pt/C as anode (+) and cathode (?) ((+)NiFe-LDH/CNFs||Pt/C(?)) only requires a potential of 1.50 V to deliver the water splitting current of 10 mA cm?2, 130 mV lower than that of (+)RuO2||Pt/C(?) couple, demonstrating great potential for applications in cost-efficient water splitting devices.  相似文献   

12.
This work demonstrates a facile Nb2O5-decorated electrocatalyst to prepare cost-effective Ni–Fe–P–Nb2O5/NF and compared HER & OER performance in alkaline media. The prepared electrocatalyst presented an outstanding electrocatalytic performance towards hydrogen evolution reaction, which required a quite low overpotential of 39.05 mV at the current density of ?10 mA cm?2 in 1 M KOH electrolyte. Moreover, the Ni–Fe–P–Nb2O5/NF catalyst also has excellent oxygen evolution efficiency, which needs only 322 mV to reach the current density of 50 mA cm?2. Furthermore, its electrocatalytic performance towards overall water splitting worked as both cathode and anode achieved a quite low potential of 1.56 V (10 mA cm?2).  相似文献   

13.
The development of hydrogen evolution activity (HER) electrocatalyst that can run durably and efficiently under the large current density is of special significance but still challengeable for the massive production of hydrogen. Herein, a CoP/Ni(OH)2 nanowire catalysts grown on Co foam (CF) with a three-dimensional heterojunction structure has been successfully prepared by electrodepositing nickel hydroxide on the surface of cobalt phosphide. The prepared CoP/Ni(OH)2–15 min sample reveals a superior HER activity and stability. It merely requires ultralow overpotentials of 108 and 175 mV to 100 and 500 mA cm?2, respectively. In addition, the long-term stability test shows that the catalyst (CoP/Ni(OH)2–15 min) can operate stably for at least 70 h at 400 mA cm?2. Utilizing NiFe-LDH/IF with high OER activity, the NiFe-LDH/IF || CoP/Ni(OH)2–15 min catalyst system possesses the same outstanding performance for overall water splitting (OWS), which can accomplish ≈ 500 mA cm?2 at 1.74 V in 1 M KOH electrolyte. Moreover, the NiFe-LDH/IF || CoP/Ni(OH)2–15 min couple can work for more than 80 h at 500 mA cm?2, indicating its a great prospect in the area of electrolysis water. Such excellent catalytic performance is mainly attributed to the armor effect of Ni(OH)2, which can not only promote the rapid decomposition of water molecules, but also prevent the loss of phosphorus and enhance the synergistic effect of CoP and Ni(OH)2. This work can offer a significant reference for the design with high-performance and durable transition metal phosphide electrocatalysts.  相似文献   

14.
The development of highly efficient catalysts using inexpensive and earth-abundant metals is a crucial factor in a large-scale commercialization of direct methanol fuel cells (DMFCs). In this study, we explored a new catalyst based on copper nanodendrites (CuNDs) supported on carbon nanofibers/poly (para-phenylenediamine) (CNF/PpPD) nanocomposite for methanol oxidation reaction (MOR). The catalyst support was prepared on a carbon paste electrode by electropolymerization of para-phenylenediamine monomer on a drop-cast carbon nanofibers network. Afterwards, CuNDs were electrodeposited on the nanocomposite through a potentiostatic method. The morphology and the structure of the prepared nanomaterials were characterized by transmission electron microscope, scanning electron microscope, energy dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscope. The results suggested that a three-dimensional nanodendritic structure consisting of Cu2O and Cu(OH)2 formed on the hybrid CNF/PpPD nanocomposite. The catalytic performance of CuNDs supported on CNF, PpPD and CNF/PpPD was evaluated for MOR under alkaline conditions. The CNF/PpPD/CuNDs exhibits a highest activity (50 mA cm?2) and stability toward MOR over 6 h, with respect to CNF/CuNDs (40 mA cm?2) and PpPD/CuNDs (36 mA cm?2). This inexpensive catalyst with high catalytic activity and stability is a promising anode catalyst for alkaline DMFC applications.  相似文献   

15.
It is an inevitable choice to find efficient and economically-friendly electrocatalysts to reduce the high overpotential of oxygen evolution reaction (OER), which is the key to improve the energy conversion efficiency of water splitting. Herein, we synthesized Cu2S/Ni3S2 catalysts on nickel foam (NF) with different molar ratios of Ni/Cu by a simple two-step hydrothermal method. Cu2S/Ni3S2-0.5@NF (CS/NS-0.5@NF) effectively reduces the overpotential of OER, displaying small overpotentials (237 mV@100 mA cm?2 and 280 mV@500 mA cm?2) in an alkaline solution, along with a low Tafel slope of 44 mV dec?1. CS/NS-0.5@NF also presents an excellent durability at a relatively high current density of 100 mA cm?2 for 100 h. The excellent performance is benefited by the prominent structural advantages and desirable compositions. The nanosheet has a high electrochemical active surface area and the porous structure is conducive to electrolyte penetration and product release. This work provides an economically-friendly Cu-based sulfide catalyst for effective electrosynthesis of OER.  相似文献   

16.
A kind of composite electrocatalysts with the structure of MoO3 nanosheets coated by ZIF67 nanocrystals and grown on the nickel foam substrate (ZIF67@MoO3 NSs@NF) is prepared and mainly used as the electrode for oxygen evolution reaction (OER) and overall water splitting. The excellent electrocatalytic activity of ZIF67@MoO3 NSs@NF are demonstrated. It can use the overpotential (?) of 178 mV and 386 mV respectively to drive 10 mA cm?2 and 50 mA cm?2. It is also observed that the ZIF67@MoO3 NSs@NF electrode has the highest initial current density (45.7 mA cm?2) at 1.618 V and can maintain more than 90% of the initial current density after 20,000 s. The ZIF67@MoO3 NSs@NF electrode also shows the small HER overpotential of 135 mV at 10 mA cm?2. Furthermore, the voltage of ZIF67@MoO3 NSs@NF as a bifunctional overall water splitting catalysts is 1.58 V at 10 mA cm?2, which is superior to another noble metal electric catalyst combination RuO2/NF(+)//Pt–C/NF(?). And the ZIF67@MoO3 NSs@NF(+)//ZIF67@MoO3 NSs@NF(?) combination can maintain more than 90% of the initial current density after 65,000 s at 1.58 V. The main reason is the composite interface of MoO3 NSs and ZIF67 phases with Co–O bonds, C–O–Mo bonds and oxygen vacancies defects facilitates the increase of the active sites and efficient electron transfer rate.  相似文献   

17.
The construction of cost-effective bifunctional electrocatalysts with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant for efficient overall water splitting. Herein, this work demonstrates a novel strategy for the synthesis of nickel-cobalt oxides/sulfides/phosphides composite (denoted as NiCoO–2P/S) nanoarrays on Ni foam. In this method, Ni–Co bimetallic oxide nanowires on Ni foam were partially phosphorized and sulfurized simultaneously in situ to yield Ni–Co oxide/sulfide/phosphide composite. The NiCoO–2P/S arrays have good interfacial effects and display many holes in the nanowires, giving it the advantage of large accessible surfaces on the nanowires and a beneficial for the release of gas bubbles, resulting in an excellent OER performance with a low overpotential (η) of 254 mV at 100 mA cm?2 and good HER activity (η10 = 143 mV at 10 mA cm?2). The electrocatalytic test results demonstrate small Tafel slopes (82 mV dec?1 for HER, 88 mV dec?1 for OER) and the satisfying durability in an alkaline electrolyte, indicating that the HER and OER activity was enhanced by the introduction of the Ni/Co sulfides and phosphides into Ni–Co oxides composite nanowires. Furthermore, the as-prepared NiCoO–2P/S catalyst can be used as both the anode and the cathode simultaneously to realize overall water splitting in the two-electrode electrolyzer. This system can be driven at low cell voltages of 1.50 and 1.68 V to achieve current densities of 10 and 100 mA cm?2, respectively. This work provides an alternative strategy to prepare high-performance bifunctional electrochemical materials and demonstrates the advantages of Ni–Co oxide/sulfide/phosphide composites for water splitting.  相似文献   

18.
Developing non-precious metal-based catalysts as the substitution of precious catalysts (Pt/C) in oxygen reduction reaction (ORR) is crucial for energy devices. Herein, a template and organic solvent-free method was adopted to synthesize Fe, B, and N doped nanoflake-like carbon materials (Fe/B/N–C) by pyrolysis of monoclinic ZIF-8 coated with iron precursors and boric acid. Benefiting from introducing B into Fe–N–C, the regulated electron cloud density of Fe-Nx sites enhance the charge transfer and promotes the ORR process. The as-synthesized Fe/B/N–C electrocatalyst shows excellent ORR activity of a half-wave potential (0.90 V vs 0.87 V of Pt/C), together with superior long-term stability (95.5% current density retention after 27 h) in alkaline media and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.74 V vs 0.82 V of Pt/C) in an acidic electrolyte. A Zn-air battery assembled with Fe/B/N–C as ORR catalyst delivers a higher open-circuit potential (1.47 V), specific capacity (759.9 mA h g?1Zn at 10 mA cm?2), peak power density (62 mW cm?2), as well as excellent durability (5 mA cm?2 for more than 160 h) compared to those with commercial Pt/C. This work provides an effective strategy to construct B doped Fe–N–C materials as nonprecious ORR catalyst. Theoretical calculations indicate that introduction of B could induce Fe-Nx species electronic configuration and is favorable for activation of OH1 intermediates to promote ORR process.  相似文献   

19.
It was found, for the first time, that the pyrolysis products of potassium ferrocyanide (K4[Fe(CN)6]) could significantly promote the electrocatalytic activity of the PdO based palladium iron composite catalyst towards ethanol oxidation reaction (EOR). In this work, huge carbon spheres (abbreviated as HCSs) were prepared firstly via a pyrolysis method using glucose and 1-butyl-3-methylimidazolium tetrafluoroborate as the starting materials. Secondly, PdO based palladium iron composites supported on HCSs (noted as PdO–Pd–Fe/HCSs) were successfully fabricated through a pyrolysis procedure employing PdO·H2O, HCSs and K4[Fe(CN)6] as the initial materials. When preparing PdO–Pd–Fe/HCSs, four different amounts of K4[Fe(CN)6] were respectively added in the preparation system producing four kinds of samples. The sample prepared in the absence of K4[Fe(CN)6] was nominated as sample b-0. And the samples prepared in the presence of 5, 10 and 20 mg K4[Fe(CN)6] were, respectively, labeled as sample b-5, b-10 and b-20. It was indicated by the XRD and XPS patterns that the metallic Pd particles were the main crystalline materials of above four samples. SEM images of all synthesized samples substantially demonstrated that the added amount of K4[Fe(CN)6] was a pivotal factor which could significantly affect the morphologies of the prepared samples. For sample b-0, besides some nanoparticles with a size close to 30 nm, a larger number of pores were created on the surface of the HCSs producing a honeycomb-shaped surface. Interestingly, aniseed shaped particles, cauliflower-like particles and irregular particles with a diameter more than 150 nm were, respectively, anchored on the HCSs surface of sample b-5, b-10 and b-20. Most of all, as indicated by CV and CA measurements, all the samples prepared in the presence of K4[Fe(CN)6] delivered much better electrocatalytic activities towards EOR when compared to the sample prepared with no addition of K4[Fe(CN)6]. For example, in the CV curves, the peak current density of the peak appearing in the positive potential scanning (peak f) for EOR on sample b-10 was nearly 6.4 times greater than that on sample b-0 (16.6 mA cm?2 vs. 2.6 mA cm?2). The significantly decreased charge transfer resistance and the remarkably enlarged electrochemical surface area were analyzed to be the main reasons for sample b-10 to exhibit the best electrocatalytic performance among all prepared samples. In general, a novel electrocatalyst consisting of PdO, Pd and the pyrolysis products of K4[Fe(CN)6] for EOR was developed in this work, which, due to its very lower preparation cost and its satisfied electrocatalytic activity towards EOR, was very helpful to the development of Pd-based EOR electrocatalyst.  相似文献   

20.
In order to reduce the cost of electrocatalysts and increase the exposure of the Ir active sites while ensuring the stability of the catalyst, a N-doped carbon nanotube (NCNT) is applied as a conductive support to confine the Ir clusters for avoiding them growing up via a modified method based on pyrolysis of a mixture of melamine, ferric chloride and iridium trichloride. It is found that Ir species in the as-obtained Ir(20)/Fe@NCNT-900 composite exist in two forms, Ir nanoclusters (1–2 nm) dotted on the wall of NCNT and the Ir atomically scattered on the Fe nanoparticles wrapped in the NCNT. Although the Ir content of Ir(20)/Fe@NCNT-900 is extremely low (~4 wt% Ir), the composite catalyst delivers excellent activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with an exceptionally low overpotential of 4.7 mV/11 mV for HER and 300 mV/270 mV for OER to drive 10 mA cm?2 in 0.5 M H2SO4/1.0 M KOH electrolyte respectively, which exceeds the commercial Pt/C (20 wt% Pt) and IrO2 benchmarks. In addition, it has much higher mass activity for OER at 1.55 V (1.78 A mg?1Ir) than those of the referenced catalysts in acid. The cell voltage of the two-electrode system assembled by Ir(20)/Fe@NCNT-900 for total water splitting in acidic and alkaline media are only 1.520 V and 1.510 V to afford 10 mA cm?2 separately, lower than that of Pt/C||IrO2 and with a good stability. Our work provides a construction method of low-content precious metal composite catalysts which can be applied in OER and overall water splitting field.  相似文献   

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