Hongyun Yue,Zhenpu Shi,Lan Wang,Xiangnan Li,Hongyu Dong,Yanhong Yin,Shuting Yang
Zn 2 SnO 4 @C/Sn composites were synthesized via the rapid calcination of a zinc-tin binary MOF under a reducing atmosphere for 1 min. Nanometal Sn, which has a good conductivity, and Zn 2 SnO 4 nanoparticles were assembled into secondary particles in the synthesized composites. The metal Sn acted as an active material and a conductive agent. The nanosized Zn 2 SnO 4 @C/Sn composites reduced the volume expansion and enhanced the electrochemical performance. Additionally, the carbon provided buffer spaces for the volume expansion of the active material. The metal Sn grew into large particles as the calcination time increased, which transformed the lithium storage process from surface controlled to diffusion controlled. When the Zn 2 SnO 4 @C/Sn composites were used as anode materials for LIBs , a superior electrochemical performance was achieved. A reversible capacity of up to 1140 mA h g −1 was obtained at a current density of 100 mA g −1 after 100 cycles. The reason for the capacity fading in the samples that were calcined for a long time was also analyzed, and the results might be helpful for researchers when designing new anode materials.
Yunzhu Wang,Yang Chen,Songshan Zhu,Di Song,Tianhao Ai,Sufang He,Yongming Luo
Steam reforming of glycerol (GSR) to produce hydrogen has been considered a sustainable and low-cost route for hydrogen production. The selection of a suitable catalyst support is crucial for achieving efficient hydrogen production at lower temperatures. CeO 2 has been widely used in heterogeneous catalysis and exhibits excellent low-temperature catalytic performance. However, different calcination mode may influence catalyst performance. In this study, the Ni/CeO 2 catalyst prepared by rapid calcination mode (Ni/CeO 2 -RC), was used for hydrogen production from GSR, and the Ni/CeO 2 catalyst with the conventional programmed-heating calcination method (Ni/CeO 2 -PC) was applied for comparison. The effect of different calcination modes on the physico-chemical properties of the catalysts was investigated through multiple characterizations such as N 2 adsorption-desorption, X-ray diffraction, hydrogen temperature programmed reduction, transmission electron microscopy, X-ray photoelectron spectroscopy, H 2 chemisorption, CO-oxygen storage capacity and conversion, temperature programmed oxidation, and Raman spectroscopy. The rapid calcination mode promoted stronger metal-support interactions in Ni/CeO 2 -RC, inducing the formation of nickel species highly susceptible to reduction due to the electronic effect. Additionally, rapid calcination facilitated the increased incorporation of nickel particles into the cerium dioxide lattice, leading to lattice distortions, thereby contributing to the formation of more oxygen vacancies. The abundant oxygen vacancies promoted the activation of water, thus realizing the high H 2 selectivity of Ni/CeO 2 -RC. Moreover, the strong oxygen storage-release ability of Ni/CeO 2 -RC facilitated the oxidative effect of carbon deposition and the strong Ni–CeO 2 interaction effectively inhibit sintering of nickel nanoparticles on Ni/CeO 2 -RC. Therefore, Ni/CeO 2 -RC exhibited outstanding catalytic stability, remaining active for 35 h without deactivation, whereas Ni/CeO 2 -PC rapidly deactivated after 25 h of reaction.
Efficient supercapacitors have attracted wide attention by the exploration of hybrid materials integrating the merits of individual components as promising electrode materials. However, the construction of advanced hybrid structures for highly enhanced electrochemical energy storage is still challenging. Herein, integration of a strong compositional synergy between various bimetallic oxides, MCo2O4 (M = Ni, Fe, and so on), and inducing rich defects for more redox sites are proposed. A novel NiCo2O4–FeCo2O4 hybrid array of nanowires with a large number of nanopores and crystal interfaces is synthesized via hydrothermal reactions and fast calcination. The performance of the NiCo2O4–FeCo2O4/carbon cloth electrode is good and is far beyond that of single-component MCo2O4 electrodes, which exhibits a specific capacity of 490 F/g at 4.0 A/g. The integration of bimetallic redox centers reconstructing the electronic coordination and the nanopores providing highly exposed active surfaces and active sites for highly efficient electrolyte ion diffusion contribute to the enhanced performance. An asymmetric solid-state supercapacitor composed of NiCo2O4–FeCo2O4 and graphene (both using carbon cloth as substrates) as the anode and cathode electrodes, respectively, exhibits a high energy density of 88.9 Wh/cm2 (at a power density of 800 mW/cm2). In particular, the flexible asymmetric device exhibits excellent deformation-tolerant electrochemical stability with nearly overlapping cyclic voltammetry curves at varying bending angles. This work proposes additional methodologies to the fabrication of excellent-performance flexible all-solid-state devices for wearable devices.
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