Water splitting has attracted more and more attention as a promising strategy for the production of clean hydrogen fuel. In this work, a new synthesis strategy was proposed, and Co0.85Se was synthesized on nickel foam as the main matrix. The doping of appropriate Cr amount into the target of Co0.85Se and the Cr‐Co0.85Se resulted in an excellent electrochemical performance. The doping of Cr introduces Cr3+ ions which substitute Co2+ and Co3+ ions in Co0.85Se, so that the lattice parameters of the main matrix were changed. It is worth noting that the Cr0.15‐Co0.85Se/NF material exhibits an excellent performance in the oxygen evolution reaction (OER) test. When the current density reaches 50 mA cm?2 for OER, the overpotential is only 240 mV. For the hydrogen evolution reaction (HER) tests, the overpotential is only 117 mV to drive 10 mA cm?2 of current density. Moreover, when the Cr0.15‐Co0.85Se/NF material is used as a two‐electrode device for whole water splitting, the required cell voltage is only 1.43 V to reach a current density of 10 mA cm?2, which is among the lowest values of the published catalysts up to now. In addition, the Cr0.15‐Co0.85Se/NF catalyst also exhibits excellent stability during a long period of water splitting. The experimental result demonstrates that the change of the lattice structure has an obvious influence on the electrocatalytic activity of the material. When an external electric field is applied, it facilitates the rapid electron transfer rate and enhances the electrocatalytic performance and stability of the material. 相似文献
A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe‐2Se precursor. The as‐synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen‐evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water‐splitting setup was fabricated using a two‐electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting. 相似文献
A series of Ni0.37Co0.63S2-reduced graphene oxide nanocomposites with different graphene contents (NCS@rGO-x) has been successfully prepared via a facile one-step hydrothermal method and applied as the catalysts for the oxygen evolution reaction (OER) and degradation of organic pollutants. The XRD and FESEM analyses revealed that the phase structure and morphology of NCS nanoparticles were substantially influenced by the graphene contents. The phase structure of NCS nanoparticles gradually transformed from primary NiCo2S4 to Ni0.37Co0.63S2 and the morphology and size of NCS nanoparticles were found to become more regular and homogeneous with the increase of graphene concentration. On the NCS@rGO-x nanocomposites, the NCS@rGO-2 sample demonstrated the best catalytic activity toward the OER, which delivers a stable current density of 10 mA cm?2 at a small overpotential of ~276 mV (vs. RHE) with a Tafel slope as low as 48 mV dec?1. Furthermore, the NCS@rGO-2 sample showed the remarkable photocatalytic activity for degradation of methylene blue (MB), which may be attributed to the increased reaction sites and high separation efficiency of photogenerated charge carries due to the electronic interaction between NCS nanoparticles and rGO. All these impressive performances indicate that the NCS@rGO-2 nanocomposite is a promising catalyst in energy and environmental fields.
Graphical abstract A series of Ni0.37Co0.63S2-reduced graphene oxide nanocomposites with different graphene contents has been successfully prepared and applied as the catalysts for the oxygen evolution reaction (OER) and degradation of organic pollutants. The NCS@rGO-2 catalyst-modified stainless steel wire mesh (SSWM) electrode delivers a stable current density of 10 mA cm?2 at a small overpotential of ~276 mV (vs. RHE) with a Tafel slope as low as 48 mV dec?1. At the same time, the NCS@rGO-2 catalyst is also first investigated as an efficient photocatalyst for degradation of MB.
Molybdenum disulfide (MoS2) or tungsten disulfide (WS2), as a promising catalyst, is widely investigated for hydrogen evolution reaction (HER). In this work, a composite electrocatalysts MoxW1-xS2 is successfully decorated on carbon fiber paper (CFP) through a facile hydrothermal method. The three-dimensional porous CFP can enable the diffusion and penetration of electrolyte. Comparing with MoS2 and WS2 catalyst, the composite electrocatalyst MoxW1-xS2 nanosheets can expose the large number of electrochemically active sites. Hence, the as-prepared MoxW1-xS2/CFP (3:1) exhibit the outstanding HER catalytic activity with the small Tafel slope of 68 mV dec?1 and the low overpotential of ??178.4?±?0.5 mV at a current density of 10 mA cm?2. Chronoamperometric current test for 18 h confirm the long-term stability of the composite electrocatalyst. 相似文献
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
The development of high-performance non-precious metal-based robust bifunctional electrocatalyst for both hydrogen evolution reaction(HER) and oxygen evolution reactions(OER) in alkaline media is essential for the electrochemical overall water splitting technologies. Herein, we demonstrate that the HER/OER performance of Co Se2 can be significantly enhanced by tuning the 3d-orbital electron filling degree through Mo doping. Both density functional theory(DFT) calculations and experime... 相似文献
We report the synthesis of NiCo2O4/reduced graphene oxide (NiCo2O4/rGO) hybrid hierarchical structures with unique nanonet and microsphere morphologies by organic polar solvent-assisted solvothermal method. The electrocatalytic oxygen evolution reaction (OER) activity of these materials is studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry methods in O2-saturated 0.1 M KOH solution. The NiCo2O4/rGO hybrid nanocomposite materials are found to be highly active electrocatalysts for OER at lower overpotentials. The nanonet and microsphere-like NiCo2O4/rGO catalysts require overpotentials of 0.450 and 0.530 V at a current density of 10 mA cm?2, and their corresponding Tafel slopes are 53 and 62 mV dec?1, which are much lower than values reported for non-precious electrocatalysts. Further, both NiCo2O4/rGO catalysts show good catalytic stability with current retention more than 92 % over long period of 15,000 s determined by chronoampirometry and at the end of 1000th cycle determined by linear sweep voltammetry. The enhanced OER activity of nanostructured NiCo2O4/rGO hybrid catalysts is attributed to synergistic interaction between rGO and NiCo2O4, which seems to be essential for maintaining the large contact area at the electrode-electrolyte interface, better mass, and charge transport and to minimize the aggregation of NiCo2O4 nanoparticles. 相似文献
Uniform Ni3C nanodots dispersed in ultrathin N‐doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni3C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni3C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni3C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec−1) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec−1 in KOH solution. Such nanodot‐incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting. 相似文献
Efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) are significant for the advancement of effective water splitting reaction. Herein, we describe the growth of cobalt molybdenum sulfide (CoMoS) at different composites of tightly packed nanocrystals, prepared by one step process of simple electrodeposition method on fluorine-doped tin oxide (FTO) substrate as highly active and low-cost HER electrocatalyst. The prepared electrocatalysts were characterized via various analytical techniques. The HER activity was evaluated through electrochemical methods such as cyclic voltammetry technique and impedance analysis. Exhaustive electrochemical examinations show that the Co0.95Mo0.05S achieved higher cathodic current density value of 14.3 mA/cm2 at η?=?250 mV with a lowest Tafel slope value towards HER. Furthermore, the active surface area of the as-deposited composite materials has been calculated by cyclic voltammetry analysis. Hence, the present work illustrates that the Co0.95Mo0.05S composite can serve as an encouraging cost-effective substitute to platinum-based electrocatalyst for HER. 相似文献
Bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte may improve the efficiency of overall water splitting. Nickel cobaltite (NiCo2O4) has been considered a promising electrode material for the OER. However, NiCo2O4 that can be used as an electrocatalyst in HER has not been studied yet. Herein, we report self‐assembled hierarchical NiCo2O4 hollow microcuboids for overall water splitting including both the HER and OER reactions. The NiCo2O4 electrode shows excellent activity toward overall water splitting, with 10 mA cm?2 water‐splitting current reached by applying just 1.65 V and 20 mA cm?2 by applying just 1.74 V across the two electrodes. The synthesis of NiCo2O4 microflowers confirms the importance of structural features for high‐performance overall water splitting. 相似文献
A mixed oxide-covered mesh electrode composed of NiCo2O4 (MOME-NiCo2O4) was prepared on a stainless-steel substrate using thermal decomposition (slow-cooling rate method). Surface, bulk and electrochemical properties of MOME were studied using different techniques, namely scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) with determination of the electrochemical porosity (?) and morphology factor (φ) parameters, quasi-stationary polarisation curves (PC) and electrochemical impedance spectroscopy (EIS). SEM images revealed a good coverage of the metallic wires by a compact oxide layer (absence of cracks). XRD analysis confirmed the formation of the spinel NiCo2O4 with the presence of NiO. The ‘in situ’ surface parameters denoted as ? and φ exhibited values of 0.39 and 0.33, respectively, revealing that the electrochemically active surface area is mainly confined to the ‘outer/external’ surface regions of the oxide layer. The PC was characterised by two Tafel slopes distributed in the low (b1 = 46 mV dec?1) and high (b2 = 59 mV dec?1) overpotential domains. The corresponding apparent exchange current densities were j0(1) = (3.43 ± 0.11) × 10?6 A cm?2 and j0(2) = (6.70 ± 0.08) × 10?6 A cm?2, respectively. The EIS study accomplished in the low-overpotential domain revealed a Tafel slope (b1) of 51 mV dec?1. According to the spin-trapping reaction using N,N-dimethyl-p-nitrosoaniline (RNO), the MOME-NiCo2O4 electrode exhibited good performance for the generation of weakly adsorbed hydroxyl radicals (HO?) during the OER in electrolyte-free water. 相似文献
The development of transition‐metal‐oxides (TMOs)‐based bifunctional catalysts toward efficient overall water splitting through delicate control of composition and structure is a challenging task. Herein, the rational design and controllable fabrication of unique heterostructured inter‐doped ruthenium–cobalt oxide [(Ru–Co)Ox] hollow nanosheet arrays on carbon cloth is reported. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, the (Ru–Co)Ox nanoarrays exhibited outstanding performance as a bifunctional catalyst. Particularly, the catalyst showed a remarkable hydrogen evolution reaction (HER) activity with an overpotential of 44.1 mV at 10 mA cm?2 and a small Tafel slope of 23.5 mV dec?1, as well as an excellent oxygen evolution reaction (OER) activity with an overpotential of 171.2 mV at 10 mA cm?2. As a result, a very low cell voltage of 1.488 V was needed at 10 mA cm?2 for alkaline overall water splitting. 相似文献
Pyrolysis of a bimetallic metal–organic framework (MIL‐88‐Fe/Ni)‐dicyandiamide composite yield a Fe and Ni containing carbonaceous material, which is an efficient bifunctional electrocatalyst for overall water splitting. FeNi3 and NiFe2O4 are found as metallic and metal oxide compounds closely embedded in an N‐doped carbon–carbon nanotube matrix. This hybrid catalyst (Fe‐Ni@NC‐CNTs) significantly promotes the charge transfer efficiency and restrains the corrosion of the metallic catalysts, which is shown in a high OER and HER activity with an overpotential of 274 and 202 mV, respectively at 10 mA cm?2 in alkaline solution. When this bifunctional catalyst was further used for H2 and O2 production in an electrochemical water‐splitting unit, it can operate in ambient conditions with a competitive gas production rate of 1.15 and 0.57 μL s?1 for hydrogen and oxygen, respectively, showing its potential for practical applications. 相似文献
One of the challenges to realize large‐scale water splitting is the lack of active and low‐cost electrocatalysts for its two half reactions: H2 and O2 evolution reactions (HER and OER). Herein, we report that cobalt‐phosphorous‐derived films (Co‐P) can act as bifunctional catalysts for overall water splitting. The as‐prepared Co‐P films exhibited remarkable catalytic performance for both HER and OER in alkaline media, with a current density of 10 mA cm?2 at overpotentials of ?94 mV for HER and 345 mV for OER and Tafel slopes of 42 and 47 mV/dec, respectively. They can be employed as catalysts on both anode and cathode for overall water splitting with 100 % Faradaic efficiency, rivalling the integrated performance of Pt and IrO2. The major composition of the as‐prepared and post‐HER films are metallic cobalt and cobalt phosphide, which partially evolved to cobalt oxide during OER. 相似文献
Transition metal oxides have great potential as anode for lithium-ion batteries (LIBs), owing to their high theoretical capacity and low cost. However, the poor cycling stability and electron conductivity have limited the widely expected application of transition metal oxides. In this work, highly single-crystalline Co3O4 cubes with 400 nm in the average side length are successfully synthesized by a facile hydrothermal method. When used as anode for LIBs, the Co3O4 single-crystalline cubes exhibit highly stable and substantial discharge capacities of the amount to 877 mA h g?1 at 200 mA g?1 after 110 cycles with remarkable capacity retention of 98%, and 576 mA h g?1 even at a high rate of 2000 mA g?1. The scalability of the preparation method and the impressive results achieved here demonstrate the potential for the application to the future development of transition metal oxides anodes. These results suggest that the single-crystalline Co3O4 is a promising electrode material for the high-performance energy storage devices. 相似文献
Designing cost‐effective and efficient electrocatalysts plays a pivotal role in advancing the development of electrochemical water splitting for hydrogen generation. Herein, multifunctional active‐center‐transferable heterostructured electrocatalysts, platinum/lithium cobalt oxide (Pt/LiCoO2) composites with Pt nanoparticles (Pt NPs) anchored on LiCoO2 nanosheets, are designed towards highly efficient water splitting. In this electrocatalyst system, the active center can be alternatively switched between Pt species and LiCoO2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Specifically, Pt species are the active centers and LiCoO2 acts as the co‐catalyst for HER, whereas the active center transfers to LiCoO2 and Pt turns into the co‐catalyst for OER. The unique architecture of Pt/LiCoO2 heterostructure provides abundant interfaces with favorable electronic structure and coordination environment towards optimal adsorption behavior of reaction intermediates. The 30 % Pt/LiCoO2 heterostructured electrocatalyst delivers low overpotentials of 61 and 285 mV to achieve 10 mA cm?2 for HER and OER in alkaline medium, respectively. 相似文献
Rational design and building of high efficiency, secure and inexpensive electrocatalyst is a pressing demand and performance to promote sustainable improvement of hydrogen energy. The bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution response (HER) with high catalytic performance and steadiness in the equal electrolyte are extra treasured and meaningful. Herein, a unique three-dimensional (3D) structure electrocatalyst for NiCo2S4 growing on the flower-like NiFeP was designed and synthesized in this study. The results show that the flower-like NiCo2S4/NiFeP/NF composite electrocatalyst has large specific surface area, appropriate electrical conductivity, and greater lively websites uncovered in the three-dimensional structure, and affords extraordinary electrocatalytic overall performance for the ordinary water splitting. In alkaline solution, the OER and HER overpotentials of NiCo2S4/NiFeP/NF only need 293 mV and 205 mV overpotential to provide the current densities of 100 mA/cm2 and 50 mA/cm2, respectively. This high electrocatalytic activity exceeds the catalytic activity of most nickel-iron based electrocatalysts for OER and HER process. Accordingly, the optimized NiCo2S4/NiFeP/NF sample has higher stability (24 h) at 1.560 and 10 mA/cm2, which extensively speeds up the overall water splitting process. In view of the above performance, this work offers a fine approach for the further improvement of low fee and excessive effectivity electrocatalyst. 相似文献
Electrochemical water splitting is a promising approach for producing sustainable and clean hydrogen. Typically, high valence state sites are favorable for oxidation evolution reaction (OER), while low valence states can facilitate hydrogen evolution reaction (HER). However, here we proposed a high valence state of Co3+ in Ni9.5Co0.5−S−FeOx hybrid as the favorable center for efficient and stable HER, while structural analogues with low chemical states showed much worse performance. As a result, the Ni9.5Co0.5−S−FeOx catalyst could drive alkaline HER with an ultra-low overpotential of 22 mV for 10 mA cm−2, and 175 mV for 1000 mA cm−2 at the industrial temperature of 60 °C, with an excellent stability over 300 h. Moreover, this material could work for both OER and HER, with a low cell voltage being 1.730 V to achieve 1000 mA cm−2 for overall water splitting at 60 °C. X-ray absorption spectroscopy (XAS) clearly identified the high valence Co3+ sites, while in situ XAS during HER and theoretical calculations revealed the favorable electron capture at Co3+ and suitable H adsorption/desorption energy around Co3+, which could accelerate the HER. The understanding of high valence states to drive reductive reactions may pave the way for the rational design of energy-related catalysts. 相似文献