| 1. |
- Liu, Chenjuan, 1988-, et al.
(författare)
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A free standing Ru–TiC nanowire array/carbon textile cathode with enhanced stability for Li–O2 batteries
- 2018
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 6, s. 23659-23668
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Tidskriftsartikel (refereegranskat)abstract
- The instability of carbon cathode materials is one of the key problems that hinder the development of lithium–air/lithium–oxygen (Li–O2) batteries. In this contribution, a type of TiC-based cathode is developed as a suitable alternative to carbon based cathodes, and its stability with respect to its surface properties is investigated. Here, a free-standing TiC nanowire array cathode was in situ grown on a carbon textile, covering its exposed surface. The TiC nanowire array, via deposition with Ru nanoparticles, showed enhanced oxygen reduction/evolution activity and cyclability, compared to the one without Ru modification. The battery performance of the Li–O2cells with Ru–TiC was investigated by using in operando synchrotron radiation powder X-ray diffraction (SR-PXD) during a full cycle. With the aid of surface analysis, the role of the cathode substrate and surface modification is demonstrated. The presented results are a further step toward a wise design of stable cathodes for Li–O2 batteries.
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| 2. |
- Ma, Yue, et al.
(författare)
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Multiscale Interfacial Strategy to Engineer Mixed Metal-Oxide Anodes toward Enhanced Cycling Efficiency
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:23, s. 20095-20105
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Tidskriftsartikel (refereegranskat)abstract
- Interconnected macro/mesoporous structures of mixed metal oxide (MMO) are developed on nickel foam as freestanding anodes for Li-ion batteries. The sustainable production is realized via a wet chemical etching process with bio-friendly chemicals. By means of divalent iron doping during an in situ recrystallization process, the as-developed MMO anodes exhibit enhanced levels of cycling efficiency. Furthermore, this atomic-scale modification coherently synergizes with the encapsulation layer across a micrometer scale. During this step, we develop a quasi-gel-state tri-copolymer, i.e., F127-resorcinol-melamine, as the N-doped carbon source to regulate the interfacial chemistry of the MMO electrodes. Electrochemical tests of the modified FexN1-xO@NC-NiF anode in both half-cell and full-cell configurations unravel the favorable suppression of the irreversible capacity loss and satisfactory cyclability at the high rates. This study highlights a proof-of-concept modification strategy across multiple scales to govern the interfacial chemical process of the electrodes toward better reversibility.
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| 3. |
- Qiu, Zhen, et al.
(författare)
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Controlled crystal growth orientation and surface charge effects in self-assembled nickel oxide nanoflakes and their activity for the oxygen evolution reaction
- 2017
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 42:47, s. 28397-28407
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Tidskriftsartikel (refereegranskat)abstract
- Although sustainable hydrogen production from solar energy is a promising route for the future, the cost of the necessary photovoltaic and photoelectrochemical devices as well as a lack of detailed understanding and control of catalyst interfaces in nanomaterials with high catalytic activity are the largest impediments to commercial implementation. Here, we report how a higher catalytic efficiency can be achieved by utilizing an earth-abundant Nickel oxide (NiO) catalyst via an improved control of the crystalline growth orientation and self-assembly. The relationship between the surface charge and the morphology of the nano-catalysts is investigated using a hydrothermal method where the pH is utilized to control both the crystal growth direction and crystallization of Ni(OH)2 and eventually in NiO, where the self-assembly properties of nanoflakes (NFs) into hierarchical flower-like nickel oxide NFs depend on balancing of forces during synthesis. The surface charge ofthe NiO at different pH values was measured with electrophoretic dynamic light scattering (EDLS) and is known to be closely related to that of Ni(OH)2 and is here utilized to control the relative change in the surface charge in the precursor solution. By preparing NiO NFs under variation of the pH conditions of the precursor Ni(OH)2 system, the surface energies of exposed lattice planes of the growing nanostructures can be altered and an enhanced crystal growth orientation in a different direction can be controlled. Specifically, the [111] and [220] growth orientation in cubic NiO can be favored or suppressed with respect to the [200] direction. Benefiting from the large surface area provided by the mesoporous NiO NFs, the catalyst electrode exhibits high activity toward the oxygen evolution reactions in alkaline electrolyte. The NiO nanostructure synthesized at pH 10 displays oxygen evolution reaction (OER) overpotential of 0.29 V and 0.35 V versus the reversible hydrogen electrode (RHE) at 1 mA cm2 and 10 mA cm2 current density, respectively. This is compared to commercial NiO with more than 0.15 V additional overpotential and the same or lower overpotential compared to RuO2 and IrO2 at alkaline conditions. The results show that the OER catalytic activity can be drastically increased by a detailed control of the crystal growth orientation and the self-assembly behavior where the active surface charge around the point of zero charge during synthesis of the metal hydroxides/oxides is introduced as an important design principle for producing efficient electrocatalysts.
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