Rationally designing high-activity catalyst for oxygen evolution reaction (OER) is of primary importance due to its sluggish kinetic process in water splitting. Herein, we report a metallic (V) and nonmetallic (F) double doping in Co3O4 with nanoneedles structure, which is synthesized through facile oil bath and annealing. Electrochemical measurements show that the Co3O4 dopped with fluorine and vanadium (F0.2-V-Co3O4-350) only needs a low overpotential of 320 mV to afford a current density of 10 mA cm?2, which is superior to commercial RuO2. The excellent electrocatalytic performance can be attributed to double doping of vanadium and fluorine which have strong electron absorption effect to optimize the density of electrons in Co3O4. Besides, nanoneedles structure can enlarge exposure of active sites. And its great durability is evaluated through 2000 cycles CV test. Furthermore, the optimal ratio of fluorine to vanadium and different annealing temperatures of the target catalyst are explored reasonably. 相似文献
The catalysts are often used in fuel cells and metal-air batteries to speed up electrochemical reactions. In this study, we prepared CoFe2O4 nanoparticles with mainly inverse spinel structure and FeCo2O4 nanoparticles with mainly spinel structure as bifunctional catalysts by hydrothermal method. After annealing at 350 °C, pure CoFe2O4 and FeCo2O4 nanoparticles with uniform size distribution have been obtained. The CoFe2O4 nanoparticles showed high current density of 5.5 mA/cm2 at −0.8 V in the ORR test. It's low Tafel slope of 83.0 mV/dec further confirmed the excellent ORR catalytic properties of CoFe2O4 nanoparticles. Furthermore, the CoFe2O4 nanoparticles also showed good OER properties with satisfied current density of 35.7 mV/cm2 at l.0 V and low OER Tafel slope of 71.0 mV/dec. Both the ORR and OER properties of CoFe2O4 nanoparticles showed good time stability which were compared with FeCo2O4 nanoparticles. These results indicated that CoFe2O4 nanoparticles with mainly inverse spinel structure had better electrocatalytic performance than FeCo2O4 nanoparticles with mainly spinel structure. The CoFe2O4 nanoparticles with mainly inverse spinel structure show a significant potential application in rechargeable battery. 相似文献
Construction of strong interactions between oxides is compelling for modulating the active sites towards acidic oxygen evolution reaction (OER) electrocatalysts. Here, a solid solution oxide electrocatalyst constructed by alloying of IrO2 and CrO2 (labeled as Ir0.3Cr0.7O2) is reported with an overpotential of 255 mV at a current density of 10 mA cm?2 for OER in 0.5 M H2SO4 solution, which is much lower than that of the state-of-the-art IrO2 (357 mV). The mass activity at 1.50 V vs. RHE is 47 folds than that of IrO2, and it can maintain such OER stability for more than 200 h. Detailed analysis concludes that the organic ligands-assisted synthesis of Ir0.3Cr0.7O2 can enlarge the surface-active area and provide more active sites for water oxidation, while the leaching of Cr and its strong interaction with Ir sites resulting in the formation of high chemical state oxides of Ir with superior activity for acidic OER. It is found that the significantly increasement of oxygen vacancies content during electrochemical test together with the two points mentioned above jointly promote the water oxidation activities of Ir0.3Cr0.7O2 electrocatalyst in acidic media. 相似文献
Herein, we designed a simple and universal method to prepare cobalt-based bimetallic ZnxCo1-x-MOFs precursors, which were used as templates to synthesize effective bifunctional electrocatalyst hollow porous ZnxCo1-xSe2 microcubes by one-step hydrothermal method. The cubic morphology of the ZnxCo1-x-MOFs precursors was well inherited. Particularly, the Zn0.1Co0.9Se2 exhibited superior HER and OER performance in acidic solution and alkaline solution, respectively. Benefiting from the hollow porous structure, the synergistic effect of Zn–Co–Se and the incorporation of a small number of zinc atoms.
Exploring highly efficient electrocatalysts (OER) is critical for oxygen evolution reaction. Herein, for the first time, P-doped NiCo2O4 nanosheet arrays generated on nickel foam (namely P–NiCo2O4/NF) were constructed via a feasible protocol. Notably, the etching treatment can open the internal structure of ZIF-67 to offer more electrocatalytically active surface area, and obtained NiCo2O4 showed great electrocatalytic performance in OER. The introduction of P can effectively reduce the charge transfer resistance of NiCo2O4 and boost OER kinetics. More importantly, doping P not only improved the hydrophilicity of NiCo2O4, but also reduced its surface potentials, which provided convenience for the adsorption of OH− over P–NiCo2O4/NF electrode. As expected, the P–NiCo2O4/NF electrode with good long-term durability displayed excellent performance for OER in alkaline solution, and an overpotential of 121.6 mV was achieved at a current density of 10 mA/cm2. To sum up, current work can provide a meaningful reference to prepare electrocatalyst for efficient OER. 相似文献
Spinel oxide electrocatalysts supported on carbon nanofibers (CNFs), denoted as and NiMn2O4/CNF and NiCo2O4/CNF, are investigated for the oxygen evolution reaction (OER) in alkaline electrolyte. NiCo2O4/CNF and NiMn2O4/CNF are prepared according to an optimized electrospinning method using polyacrylonitrile (PAN) as carbon nanofibers precursor. After the thermal treatment at 900 °C for 1 h in the presence of helium and the subsequent one at 350 °C for 1 h in air, nanosized metal oxides with a spinel structure supported on carbon nanofibers are obtained. The physico-chemical investigation shows relevant difference in the crystallite size (9 nm for the NiCo2O4/CNF and 20 nm for the NiMn2O4/CNF) and a more homogeneous distribution for NiMn2O4 supported on carbon nanofibers. These characteristics derive from the different catalytic effects of Co and Mn during the thermal treatment as demonstrated by thermal analysis. The OER activity of NiCo2O4/CNF and NiMn2O4/CNF is studied in a single cell based on a zero gap anion-exchange membrane-electrode assembly (MEA). The NiMn2O4/CNF shows a better mass activity than NiCo2O4/CNF at 50 °C (116 A g−1 @ 1.5 V and 362 A g−1 @ 1.8 V vs. 39 A g−1 @ 1.5 V and 253 A g−1 @ 1.8 V) but lower current density at specific potentials. This is the consequence of a lower concentration of the active phase on the support resulting from the need to mitigate the particle growth in NiMn2O4/CNF. 相似文献
The aim of this work is to investigate the natural mineral Montmorillonite (MMT) as catalytic support and to assess the efficiency of the composite MMT-supported Ir toward OER in acidic electrochemical water splitting. MMT is a phyllosilicate layered clay with 2:1 type sheet structure with high cation exchange capacity, high surface area and low cost. Three different catalyst with iridium loadings of 10, 20, and 30 wt% Ir supported on MMT are synthesized. Their phase identification, crystallite size, elemental analysis, and thermal stability are studied by means of XRD, HRTEM, EDX, and TGA, respectively. The catalytic performance is examined in 0.5 M H2SO4 and in electrolysis cell with proton conductive polymer membrane (PEMEC). The results obtained prove that montmorillonite is a promising alternative of the conventional carbon supports with the advantage of being both easily available and cost favourable. Ir/MMT loaded with 30 wt% Ir is the best performed catalyst. In PEMEC operated at 80 °C the catalyst loading of 0.5 mgIr cm?2 ensures intensive and sustainable oxygen evolution with current density reaching 200 mA cm?2 already at 1.6 V. 相似文献
The application of electrochemical water splitting process in acidic medium is restricted by the lack of highly efficient and stable oxygen evolution reaction (OER) electrocatalyst. In this work, we report a facile soft template method to synthesize nanosized iridium oxide for electrocatalytic OER in acidic medium. The fabrication process involves thermal treatment of iridium complex and polypyrrole in air. The compositions and structures of the resulting catalytic materials are significantly influenced by the annealing temperature. The nanostructured iridium oxide synthesized at optimal 450 °C exhibits low overpotential (291.3 ± 6 mV) to reach 10 mA/cm2 current density towards OER, which is better than the commercial iridium oxide. Further investigation indicates that nanosized iridium oxide synthesized at 450 °C has high electrochemical active surface area to expose abundant accessible active sites, which can accelerate the OER rate. This method can also provide new guidance to prepare other metal oxide nanoparticles for various applications. 相似文献
In the present work, graphene supported IrO2 catalyst (IrO2/RGO) has been synthesized by hydrothermal method in ethanol/water mixture solvent. X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests reveal that IrO2 is uniformly supported on RGO surface with ultrafine IrO2 nanoparticles (ca. 1.7 nm). Linear sweep voltammetry (LSV) tests indicate that the catalytic activity of IrO2/RGO hybrid towards oxygen evolution reaction (OER) is 2.3 times that of commercial IrO2. The superior OER activity of IrO2/RGO hybrid is attributed to the enhanced surface area and the improved electrical conductivity of IrO2 due to the introduction of graphene support. Lifetime tests demonstrate that IrO2/RGO hybrid has unexpectedly high OER durability. It also displays an excellent performance in long-time water electrolysis. This may be interpreted in terms of the dispersion retention of IrO2 nanoparticles on RGO surface, which is caused by the interaction between IrO2 and Π-electrons of RGO. 相似文献
Active and highly stable oxygen evolution reaction (OER) electrocatalyst for PEM-based water electrolysis are currently in high demand. Herein, we report a rutile iridium-titanium oxide solid solution (IrTiOx) through a facile one-step annealing of a Ti-based metal-organic framework precursor. The composite exhibits excellent OER activity and stability in acidic media, with a low overpotential of 296 mV at 10 mA cm−2 while the OER activity was retained during a 100-h galvanostatic stability test at a constant current of 10 mA cm−2 in 0.5 M H2SO4, outperforming the state-of-the-art IrO2-based electrocatalysts. We further demonstrate the structure evolution of iridium-titanium oxide during OER operations. In contrast to the initial uniform distribution of Ir and Ti over the entire architecture, after OER stability test, a hollow morphology is formed, in which the particle surface is covered with an IrOx-rich layer and entire particle becomes hollow. We ascribe the structure evolution to the Ir/Ti leaching and redeposition during the OER operations. We propose that the structure evolution of iridium-titanium oxide during the electrochemical process is responsible for the high OER activity and stability of IrTiOx. 相似文献
The design of efficient electrocatalysts for oxygen evolution reaction (OER) is an essential task in developing sustainable water splitting technology for the production of hydrogen. In this work, manganese cobalt spinel oxides with a general formula of MnxCo3-xO4 (x = 0, 0.5, 1, 1.5, 2) were synthesised via a soft chemistry method. Non-equilibrium mixed powder compositions were produced, resulting in high electrocatalytic activity. The oxygen evolution reaction was evaluated in an alkaline medium (1 M KOH). It was shown that the addition of Mn (up to x ≤ 1) to the cubic Co3O4 phase results in an increase of the electrocatalytic performance. The lowest overpotential was obtained for the composition designated as MnCo2O4, which exhibited a dual-phase structure (∼30% Co3O4 + 70% Mn1.4Co1.6O4): the benchmark current density of 10 mA cm−2 was achieved at the relatively low overpotential of 327 mV. The corresponding Tafel slope was determined to be ∼79 mV dec−1. Stabilities of the electrodes were tested for 25 h, showing degradation of the MnCo2O4 powder, but no degradation, or even a slight activation for other spinels. 相似文献
The design and manufacture of strongly engaged, low-cost, and resilient oxygen evolution reaction (OER) electrocatalysts is the most challenging task in electrochemical hydrolysis. Herein, Ce and Ni co-doped MnO2 (NiCe/MnO2) nanosheets (NSs) with oxygen vacancy (VO) and abundant active sites have been prepared in one step employing a defect strategy. The co-doping of Ce/Ni on the one hand reduced the catalyst particle size and increased the specific surface area, which promoted the exposure of more active sites. On the other hand, heteroatom doping altered the species the crystalline surface, stimulating the formation of Vo and thus activating the catalyst performance simultaneously. The OER performance of NiCe/MnO2 NSs was significantly enhanced over the pure δ-MnO2, with an overpotential of 170 mV (10 mA cm?2), which was verified by density functional theory. This work shows a straightforward and practical method for making non-precious metal electrocatalysts with high electrochemical hydrolysis performance. 相似文献
Rational design of efficient oxygen evolution reaction (OER) electrocatalysts plays a significant role in various applications like water splitting and metal-air batteries. Simultaneous modulation of geometric and electronic structure is a promising strategy for boosting the electrocatalytic active of OER catalysts. Herein, a novel type of Mn doped Co9S8 supported on N-enriched porous carbon polyhedron composite material (Mn–Co9S8/NC) is constructed via absorption-pyrolysis-sulfurization treatment of Zeolitic-imidazolate frameworks (ZIF-67). ZIF-67 derived N-enriched porous carbon polyhedron serves as the porous skeleton for anchoring numerous Co9S8 nanoparticles. The results confirm that the incorporation of Mn in Co9S8/NC can improve the degree of graphitization compared with Co9S8/NC, implying the enhancement of the conductivity. Meanwhile, the incorporation of Mn can lead to electronic modulation of Co species to bump up the intrinsic activity of active site in Mn–Co9S8/NC. Due to the synergistic effect of Mn, Co9S8 and porous carbon structure, the specific surface area and electronic structure are optimized, endowing the maximum utilization of active sites. The Mn–Co9S8/NC electrocatalyst exhibits superior OER activity with the overpotential of 286 mV at current density of 10 mA cm−2 in 1.0 M KOH electrolyte. This work provides prospective insights into the synergistic coupling of geometric and electronic structure of Metal-Organic Frameworks (MOFs) material for efficient electrocatalysts. 相似文献
The electrocatalytic water splitting consists of two half-reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which require low-cost and highly activity catalysts. Two-dimensional transition metal carbon-nitride (MXenes) are considered as the potential catalysts candidates for HER and OER due to their unique physical and chemical properties. In this work, using density functional theory (DFT), we have investigated the effect of single non-metal (NM, NM = B, N, P, and S) atoms doping, strain, and terminal types on the HER and OER activities of V2CO2 MXene. Results indicated that P doping V2CO2 (P/V2CO2) has best HER performance at hydrogen coverage of θ = 1/8, and N doping V2CO2 (N/V2CO2) has best OER performance among the studied systems. In addition, it can be found that there is a strong correlation between the ΔGH and strain, ΔGH and valence charges of the doped atoms after applying strain to the doping structures, with the correlation coefficient (R2) about equal 1. Moreover, the mixed terminal can enhance the performances of HER and OER, which obey the follow rules: mixed terminal (O1 and 1OH) > original terminal (O1) > 1OH terminal. The ab initio molecular dynamics simulations (AIMD) results revealed that the single non-metallic doped structures are stable and can be synthesized experimentally at different terminals. 相似文献
Molybdenum silicides are promising electrocatalysts for hydrogen evolution in acidic environment due to their dual characteristics of metal and ceramics as well as high electrical conductivity and acid resistance. At present, most of the transition metal silicides were synthesized at high temperature, resulting in large particle size and small specific surface area, which seriously limits their electrocatalytic applications. Herein, we report a low temperature strategy for the synthesis of ultrafine Mo5Si3 and MoSi2 nanoparticles with diameter of ～5 nm by molten salt method. Results show that both of them demonstrated excellent electrocatalytic hydrogen evolution activity and stability in 0.5 M H2SO4 solution, in which the overpotentials of Mo5Si3 and MoSi2 nanoparticles at 10 mA cm?2 are 80 mV and 94 mV, respectively. This general strategy may light up the preparation of ultrafine transition metal silicides nanoparticles and facilitate their applications in electrocatalytic areas. 相似文献
This work reports utilised of RGO from Sengon wood biomass to support Fe–N–C noble-free catalyst (Fe–N-RGO), while also attempt to investigate the effect of pyrolysis stage on Fe–N-RGO catalysts with four different nitrogen precursors towards the ORR activity in acidic medium. One- and two-step pyrolysis were performed at 900 °C for 1 h and 2 h respectively to produce Fe–N-RGO. This work revealed that two-step pyrolysis was able to remove the volatile components and hence forming more graphitised, stable graphitic-N and Fe-Nx, synergistically improve the ORR activity with highest onset potential of 0.83 V vs RHE and limiting current density of 5.33 mA cm−2 reported on Fe-Pani-RGO 2py. An increase in the kinetic on Fe-Pani-RGO 2py with Tafel slope of 74 mV/dec operated at 80 °C was reported. The mesoporous structure on RGO increases the stability by 8% and better methanol tolerance when compared to a benchmark Pt/C catalyst. 相似文献
IrO2 and RuO2 are known as two of the best catalysts for the oxygen evolution reaction (OER) in acidic electrolyte. It is reported that RuO2 has higher OER catalytic activity, while IrO2 possesses better electrochemical stability during the OER process in acid. Therefore, many combined strategies have been proposed to utilize the advantages of both IrO2 and RuO2 catalysts in water electrolysis applications. In this article we describe how, by tuning the wet-chemical synthesis process in which the Ir precursor is added after the synthesis of RuO2 nanoparticles (NPs) (two-step), the Ru0.5Ir0.5O2 NPs have been synthesized to improve the OER catalytic activity in both acidic and alkaline media. In detail, the specific OER activity of the Ru0.5Ir0.5O2 NPs (with a particle size of ca. 10 nm) is 48.9 μA cm−2 at an overpotential ŋ = 0.22 V (vs. RHE) and 21.7 μA cm−2 at ŋ = 0.27 V (vs. RHE) in 0.1 M HClO4 and 0.1 M KOH, respectively. These values are higher than those for the one-step (Ir0.5+Ru0.5)O2 NPs (obtained by contemporaneously adding both Ru and Ir precursors), which are 19.5 and 15.5 μA cm−2 at the same measuring conditions, respectively. Additionally, with more IrO2 component distributed on the particle surface, the two-step Ru0.5Ir0.5O2 NPs show better OER catalytic stability than RuO2 NPs. 相似文献
Spinel-type nickel cobaltite with numerous oxygen vacancies is successfully synthesized by hydrothermal and thermal reduction using hydrogen. The effects of oxygen vacancies on the electrochemical activity and stability for the oxygen reduction reaction are investigated. The prepared catalyst displays significantly enhanced oxygen reduction reaction (ORR) catalytic performance under alkaline conditions, which is comparable to that of commercial Pt/C. The oxygen-deficient NiCo2O4 exhibits a very high limiting current density of −5.44 mA cm−2 with onset and half-wave potentials of 0.93 and 0.78 V versus the reversible hydrogen electrode (RHE), respectively. Additionally, it shows excellent durability and resistance to methanol. The enhanced ORR activity and stability of the catalyst can be ascribed to the synergistic effects of the relatively large electrochemical surface area, more exposed active sites, and good electrical conductivity derived from abundant oxygen vacancies. 相似文献
The development of highly active and low-cost catalysts for hydrogen evolution reaction (HER) is significant for the development of clean and renewable energy research. Owing to the low H adsorption free energy, molybdenum disulfide (MoS2) is regarded as a promising candidate for HER, but it shows low activity for oxygen evolution reaction (OER). Herein, graphene-supported cobalt-doped ultrathin molybdenum disulfide (Co–MoS2/rGO) was synthesized via a one-pot hydrothermal method. The obtained hybrids modified electrode exhibits a high HER catalytic activity with a low overpotential of 147 mV at the current density of 10 mA cm−2, a small Tafel slope of 49.5 mV dec−1, as well as good electrochemical stability in acidic electrolyte. Meanwhile, the catalyst shows remarkable OER activity with a low overpotential of 347 mV at 10 mA cm−2. The superior activity is ascribed not only to the high conductivity originated from the reduced graphene, but also to the synergistic effect between MoS2 and cobalt. 相似文献
The development of efficient bifunctional catalysts for both oxygen reduction and oxygen evolution reactions is highly desirable but challenging in energy conversion and storage systems. Here, a simple yet cost-effective strategy is developed to produce heteroatom-doped carbon nanospheres using natural cuttlefish ink as the precursor. For the oxygen reduction reaction, the catalyst exhibits more positive onset-potential and larger diffusion limiting current density compared with benchmark platinum catalyst in alkaline medium. Moreover, the as synthesized catalyst shows low onset-potential for oxygen evolution reaction, indicating its outstanding catalytic activity. The catalyst shows a potential gap of 0.75 V between the oxygen evolution reaction potential at a current density of 10 mA cm?2 and the oxygen reduction reaction potential at the half-wave potential, outperforming most of other noble metal-free carbon catalysts in the current state of research. The remarkable catalytic performance can be assigned to heteroatoms doping, full exposure of the active sites, large surface area and enrichment of pores for sufficient contact and rapid transportation of the reactants. This study offers a new approach for the synthesis of metal-free carbon nanomaterials from natural resources, and broadens the design for the fabrication of bifunctional oxygen reduction and oxygen evolution catalysts. 相似文献
