RESUMEN
Binary metal nickel-iron alloys have been proven to have great potential in oxygen evolution reaction (OER) electrocatalysis, but there are still certain challenges in how to construct more efficient nickel-iron alloy electrocatalysts and maximize their own advantages. In this work, a heterometallic nickel-iron cluster (L = C64 H66 Fe4 N8 Ni2 O19 ) of Schiff base (LH3 = 2-amino-1,3-propanediol salicylaldehyde) is designed as a precursor to explore its behavior in the pyrolysis process under inert atmosphere. The combination of TG-MS, morphology, and X-ray characterization techniques shows that the Schiff base ligands in the heterometallic clusters produces a strong reductive atmosphere during pyrolysis, which enable the two 3d metals Ni and Fe to form NiFe alloys. Moreover, Fe2 O3 /Fe0.64 Ni0.36 @Cs carbon nanomaterials are formed, in which Fe2 O3 /Fe0.64 Ni0.36 is the potential active material for OER. It is also found that the centrosymmetric structure of the heterometallic Schiff base precursor is potentially related to the formation of the Fe2 O3 /Fe0.64 Ni0.36 alloy@carbon structures. The Fe2 O3 /Fe0.64 Ni0.36 @C-800 provides 274 mV overpotential in 1 m KOH solution at 10 mA cm-2 in OER. This work provides an effective basis for further research on Schiff base bimetallic doping-derived carbon nanomaterials as excellent OER electrocatalysts.
RESUMEN
NiFe alloys are among the most promising electrocatalysts for oxygen evolution reaction (OER). However, a comprehensive study is yet to be done to reveal the surface structure-performance relationship of NiFe alloys. In particular, the role of the ultrathin surface oxide layer, which is unavoidable for pure NiFe alloys, is always neglected. Herein, a series of NiFe alloys with different Ni/Fe ratios are fabricated. It is found that different Ni/Fe ratios lead to significant differences in surface composition and structure of the NiFe alloys, and thus affect their catalytic performance. Then, the oxide/metal interface of the Ni4Fe1 alloy is tailored by adjusting the hydrogenation temperature to further understand the surface structure-activity relationship, and the optimal OER performance is achieved at the oxide/metal interfaces that have suitable surface Fe/Ni ratio and an appropriate amount of oxygen vacancies. In-situ Raman characterization shows that the Ni4Fe1 alloy with well-tailored oxide/metal interface facilitates the formation of active species. Density functional theory calculations demonstrate that the ultrathin surface oxide layers are responsible for the high catalytic activity of the NiFe alloys, and that the quantity of oxygen vacancies in the surface oxides affects the adsorption energy of O* and thus to a great extent determines the catalytic activity.
RESUMEN
The rational design and exploration of the oxygen evolution reaction (OER) electrocatalysts with high efficiency, low cost, and long-term durability are extremely important for overall water splitting. Recently, numerous studies have shown that the OER reaction kinetics can be modified by optimizing components, introducing carbon matrix, and regulating porous nanostructures. Herein, a flexible and controllable electrospinning strategy is proposed to construct porous nitrogen (N)-doped carbon (C) nanofibers (NFs) with nickel-iron (NiFe) alloy nanoparticles encapsulated inside (NiFe@NCNFs) as an OER electrocatalyst. Benefiting from the strong synergistic effects that stem from the one-dimensional mesoporous structures with optimized binary metal components encapsulated in the N-doped carbon nanofibers, the NiFe@NCNFs exhibits enhanced OER performance with a low overpotential (294 mV at 10 mA cm-2) and excellent durability (over 10 h at 10 mA cm-2) in alkaline solution. Both experimental characterizations and density functional theory (DFT) calculations validate that a suitable binary metal ratio can lead to the optimal catalytic activity. Moreover, a two-electrode electrolyzer is assembled by using NiFe@NCNFs anode and Pt/C cathode in 1.0 M KOH media for the overall water splitting, which delivers an initial cell voltage of only 1.531 V at 10 mA cm-2, as well as long-term stability up to 20 h. This study sheds light on the design and large-scale production of low-cost and high-performance electrocatalysts toward different energy applications in the future.
RESUMEN
A bubble-releasing assisted pulse electrodeposition method was developed to create metallic alloy, NiFe, nanotube arrays in one step. The NiFe alloy nanotube array exhibited excellent bifunctional electrolytic activities, achieving low overpotentials of 100 mV for the hydrogen evolution reaction and 236 mV for the oxygen evolution reaction at 10 mA cm-2, both in 1 M KOH at room temperature. For overall water splitting, the NiFe alloy nanotube array delivered 10 mA cm-2 at an ultralow cell voltage of 1.58 V, among the top tier of the state-of-the-art bifunctional electrocatalysts. The NiFe alloy nanotube array also exhibited ultrastability at high current densities, experiencing only a minor chronoamperometric decay of 6.5% after a 24 h operation at 400 mA cm-2. The success of the present binder-free nanotube array-based electrode can be attributed to the much enlarged reaction surface area, one-dimensionally guided charge transport and mass transfer offered by the nanotube structure, and improved product crystallinity provided by the pulse current electrodeposition. The nanotube array structure proves to be a promising new architecture design for electrocatalysts.
RESUMEN
Tuning the crystal phase of metal alloy nanomaterials has been proved a significant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully developed a simple strategy to controllably synthesize a rare crystal structure of hexagonal close-packed (hcp) NiFe nanoparticle (NP) encapsulated in a N-doped carbon (NC) shell (hcp-NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions, in which the hcp-NiFe@NC exhibits superior OER activity compared to the conventional face-centered cubic (fcc) NiFe encapsulated in a N-doped carbon shell (fcc-NiFe@NC). At the current densities of 10 and 100â mA cm-2 , the hcp-NiFe@NC with Fe/Ni ratio of ≈5.4 % only needs ultralow overpotentials of 226â mV and 263â mV versus reversible hydrogen electrode in 1.0 m KOH electrolyte, respectively, which were extremely lower than those of fcc-NiFe@NC and most of other reported NiFe-based electrocatalysts. We proposed that hcp-NiFe possesses favorable electronic property to expedite the reaction on the NC surface, resulting higher catalytic activity for OER. This research provides a new insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
RESUMEN
A NiFe alloy nanoparticle/graphene oxide hybrid (NiFe/GO) was prepared for electrochemical glucose sensing. The as-prepared NiFe/GO hybrid was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that NiFe alloy nanoparticles can be successfully deposited on GO. The electrochemical glucose sensing performance of the as-prepared NiFe/GO hybrid was studied by cyclic voltammetry and amperometric measurement. Results showed that the NiFe/GO-modified glassy carbon electrode had sensitivity of 173 µA mM-1 cm-2 for glucose sensing with a linear range up to 5 mM, which is superior to that of commonly used Ni nanoparticles. Furthermore, high selectivity for glucose detection could be achieved by the NiFe/GO hybrid. All the results demonstrated that the NiFe/GO hybrid has promise for application in electrochemical glucose sensing.
RESUMEN
Herein, NixFe1-xOOH/NiFe/NixFe1-xOOH sandwich-structured nanotube arrays (SNTAs) supported on carbon fiber cloth (CFC) (NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC) have been developed as flexible high-performance oxygen evolution reaction (OER) catalysts by a facile in situ electrochemical oxidation of NiFe metallic alloy nanotube arrays during oxygen evolution process. Benefiting from the advantages of high conductivity, hollow nanotube array, and porous structure, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibited a low overpotential of â¼220 mV at the current density of 10 mA cm-2 and a small Tafel slope of 57 mV dec-1 in alkaline solution, both of which are smaller than those of most OER electrocatalysts. Furthermore, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibits excellent stability at 100 mA cm-2 for more than 30 h. It is believed that the present work can provide a valuable route for the design and synthesis of inexpensive and efficient OER electrocatalysts.