查看更多>>摘要：? 2022 Elsevier B.V.High specific surface area (SSA) and optimized porous structures are necessary for supercapacitors electrodes. MOFs have porous structure which make them potential candidates for electrodes materials. Here, a MOF derivative with Ni@NiOx nanoparticles embedded in porous carbon nanosheets (Ni@NiOx/C) is prepared by hydrothermal method and carbonization process. Among them, the porous structure is tuned by the ZnO templates. Results show that the amount of doped ZnO nanoparticles can affect the morphology, porous structure and electrochemical properties of Ni@NiOx/C nanosheets electrodes. In three electrode system, the Ni@NiOx/C-2 electrode has a high specific capacitance of 752 F g?1 (at 1 A g?1) and prominent rate performance (the initial capacitance retains 56% when the current density increased to 100 A g?1). After 10,000 cycles, 99% of the initial capacitance is maintained. The assembled asymmetric device (Ni@NiOx/C-2//AC) also exhibits a high-power density (15,840 W kg?1).
查看更多>>摘要：? 2022Develop efficient earth-abundant electrocatalysts for water oxidation is of great importance to construct sustainable hydrogen energy system. The dual metal CoFe layered double hydroxides (LDHs) have been regarded as one kind of most promising oxygen evolution reaction (OER) catalysts due to their excellent catalytic performance. However, fundamental understanding of the effect of Fe on OER performance of CoFe-LDHs is still unclear. In this work, we report a series of CoxFey-LDHs nanosheets with different doping amount of Fe ranging from 5% to 20% (molar ratio). We systematically characterize structure and morphology of obtained CoxFey-LDHs nanosheets. Electrochemical results demonstrate that the introduction of Fe can significantly improve catalytic activity of these CoxFey-LDHs for OER with a negative shift of> 70 mV compared to pure Co(OH)2. Furthermore, optimized Co0.85Fe0.15-LDHs exhibits high intrinsic activity compared to other CoFe-LDHs nanosheets. The formation of CoIV=O species is the rate-determining step of OER for Co0.85Fe0.15-LDHs. Theoretical and experimental results indicate that CoxFey-LDHs exhibits enhanced conductivity and charge transfer compared to pure Co(OH)2. This work provides a better understanding of the effect of Fe on the OER performance of CoxFey-LDHs nanosheets.
查看更多>>摘要：? 2022 Elsevier B.V.High-temperature multilayer ceramic capacitors (HT-MLCCs) are indispensable key basic components in high-temperature electronic equipment. Obtaining practical HT-MLCCs requires not only a high-temperature dielectric with excellent temperature stability, but also a good match between the inner electrode and the dielectric. In this work, a quaternary lead-free system (1-x) (0.64Na0.5Bi0.5TiO3-0.16 K0.5Bi0.5TiO3-0.20Bi(Mg2/3Nb1/3)O3)-xCaZrO3 (NBT-KBT-BMN-xCZ) was investigated as candidates for high-temperature dielectric. The introduction of CZ can adjust the composition of different types of polar nanoregions (PNRs) and weaken the ferroelectric coupling behavior, thereby achieving the flattening of the dielectric temperature curve. Among all the components, NBT-KBT-BMN-0.06CZ (0.06CZ) has the most excellent high-temperature dielectric properties, and is further used to match the two inner electrodes of Pt and Ag/Pd to make HT-MLCCs. The results show that for Pt-MLCC, co-firing causes a second phase MgTi2O5 to appear at the heterogeneous interface, resulting in incomplete inner electrodes, lower dielectric permittivity and increased loss in the high-temperature region. In contrast, for Ag/Pd-MLCC, the heterogeneous interface is well bonded, the inner electrode is continuous and complete and there is no second phase, which makes the capacitor show excellent dielectric performance (εr=1393±15%, tanδ≤0.025) over a wide range of 129–404 °C. This work provides an important solution for the development of a new generation of HT-MLCCs.
查看更多>>摘要：? 2022 Elsevier B.V.Improving the high-voltage stability of cathode materials is a new strategy to enhance the energy density of lithium-ion batteries (LIBs) in recent years. However, as a traditional cathode material, the low reversible capacity at high cut-off voltages (≥ 4.3 V) greatly restricts the application of LiCoO2. Herein, we have rationally synthesized a novel single-crystalline LiNi0.55Co0.15Mn0.3O2 cathode material (Z-NCM@B) by using the synergistic effect of Zr-doping and B2O3-coating. Excitedly, the modified Z-NCM@B cathode material shows improved high-voltage stability and excellent long-term cycling performance. Furthermore, it is revealed that the stronger Zr–O bond formed by Zr4+ dopant can stabilize the crystal structure and promote the migration of Li+ in the cathode materials. Meanwhile, the uniform B2O3 coating layer effectively suppresses the material corrosion by electrolyte and reduces the loss of transition metal ions during the charge/discharge cycle process. As anticipated, the Z2-NCM@B2 || graphite pouch-type full cell exhibits an advanced capacity retention of 96.9% over 250 cycles at an operating voltage of 4.2 V, while the capacity retention of the pristine NCM is only 88%. Besides, the Z2-NCM@B2 coin-cell retains a discharge capacity of 145.2 mA h g?1 at 1 C with a satisfactory capacity retention of 79.2% after 100 cycles within a broad voltage range between 2.95 and 4.7 V, which is much superior than that for the pristine NCM (130.9 mA h g?1, 70.9%). This synergistic modification strategy offers a reference for the practical application of NCM cathode materials with high-voltage stability and long-term cycling performance in LIBs.
查看更多>>摘要：? 2022 Elsevier B.V.Oxygen evolution reaction (OER) electrocatalysts play an important role in producing high purity hydrogen fuels in the water splitting reaction. However, developing bulk catalytic electrode with low-cost and efficient activity for OER is still a challenge. In this paper, the porous bulk NiFe alloys with nanosheet structure were fabricated by a facile microwave sintering powder metallurgy method coupled with Zn as space holder. The obtained porous bulk Ni0.75Fe0.25 alloy exhibits the high catalytic activity for OER with a low overpotential of 235 mV at 100 mA cm?2, a small Tafel slope of 26.1 mV dec?1 and superior stability in 1.0 M KOH. In addition, the residual Zn in the porous NiFe alloy can be dissolved to further improve the specific surface area, and a metal (oxy)hydroxide amorphous layer is formed through electrochemical self-reconstruction during the OER process. This Zn-doped porous bulk NiFe catalyst with high OER catalytic performance and outstanding stability can become a promising candidate for commercial water splitting.
查看更多>>摘要：? 2022A 2D–3D (ZnO/In2S3 heterojunction) photoanodes have been grown via a two-step physical vapor deposition (PVD) technique for ZnO, followed by chemical vapor deposition (CVD) for In2S3 2D nanolayers to study the photoelectrochemical (PEC) properties in the present study. 2D nanolayers of In2S3 deposited on ZnO thin film provide increased surface area and efficient electron-hole separation at the heterojunction interface which results in a significant reinforcement of photocurrent density and incident photon-to-current conversion efficiency (IPCE). The ZnO/In2S3 heterojunction shows a photocurrent density of 2.4 mAcm?2 at 1.23 V vs. RHE and IPCE value of 43% at 0.5 V with the stability of more than 100 min in comparison to both pristine ZnO and In2S3 samples. Measurements of photocurrent density at different wavelengths for the heterojunction sample confirm that the enhancement in photoelectrical response at the interface is due to higher absorption in the visible range as compared to pristine ZnO thin films and increased carrier separation at the interface in comparison to the pristine 2D In2S3 nanolayers. The experimental determination of the work function (KPFM), valence band offset (XPS), and bandgap values (absorption spectra) confirm favorable type II band alignment resulting in efficient charge transfer within the heterojunction sample. The present approach can be extended to other 2D heterojunction systems having unique optical and electronic properties.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, two-dimensional (2D) based photocatalysts containing TiO2 nanosheets (TNs) and reduced graphene oxide (rGO(x)) were fabricated using a hydrothermal method. Various quantities of cobalt atoms were deposited on TNs/rGO(x) by the photocatalytic deposition method (Co(y)/TNs/rGO(x)). The results of XRD and Raman spectroscopy analyses showed that the TNs have a pure anatase phase and graphene oxide was adequately reduced during the hydrothermal condition. Based on the DRS analysis, it was observed that the band gap energy of the synthesized samples was decreased compared to the one for pure TNs. The highest photocatalytic activity was obtained by the Co(76)/TNs/rGO(5) sample with 71.5% degradation of tetracycline (TC) (30 mg/L) under the visible light after 180 min. The active species scavenging tests also showed that OH? and h+ were the main species involved in the degradation of TC. The Co(76)/TNs /rGO(5) sample recovery and reusage experiments did not show a significant reduction in the photocatalytic performance after five consecutive cycles. Finally, the Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) models were developed to predict the photocatalytic degradation performance of the fabricated photocatalysts. Both the experimental and modeling results confirmed that the 2D-based photocatalysts developed in this study can be considered as promising candidates for wastewater treatment applications.
查看更多>>摘要：? 2022 The Author(s)The influence of excess Mn on the magnetoelastic ferromagnetic-to-antiferromagnetic transition Tt in the magnetocaloric compound (Mn,Cr)2Sb has been studied. With increasing excess Mn the magnetoelastic transition temperature for (Mn,Cr)2Sb initially increases and then decreases. This trend is accompanied by a strong reduction of the (Mn,Cr)Sb secondary phase. With increasing excess Mn a higher Cr content was found in the (Mn,Cr)Sb secondary phase in comparison to the matrix phase. This competition for Cr leads to a nonlinear dependence of Tt with increasing excess Mn at a fixed nominal Cr content. However, we observed that Tt depends linear on the c/a ratio for a wide range of temperatures from 170 to 350 K. A compositional diagram of the c/a ratio was constructed to assist the selection of (Mn,Cr)2Sb alloys with a desired transition temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Development of the structural, anti-wetting and exothermic stability of composite metal based-energetic composite is still a great challenge, especially used in complex environments (e.g. moisture circumstances). Thus, this paper firstly proposed electrophoretic controlled assembly (ECA) technique and facile modification process to construct the multifunctional nano-Al based NiO/perfluorosilane energetic composite films with even distribution of nanoscale particles and triple (a: microstructure, b: anti-wetting and c: exothermic performance) stability of for three years. The ECA dynamics study of Al/NiO particles was deeply explored as a “controlled bridge” to adjusting the reaction ratio of Al to NiO in product. The target film displays an outstanding high water contact angle of 171 ± 1° with an almost perfect sphere of droplet placed on that surface, and shows a small fluctuation of anti-wetting ability after immersed and exposure tests. In addition, the total heat output (Q) of product can reach up to ~2.5 kJ/g with a low activation energy of 247.624 kJ/mol, and shows ultra-long exothermic stability for three years. The realization of target film highly compatible with microelectromechanical systems (MEMS) here will largely improve the safety level of propellant or detonator system.
查看更多>>摘要：? 2021 Elsevier B.V.The publisher regret to inform thatFig. 5. a and b are missing from the article. Fig. 5.a and b are shown below. The publisher would like to apologise for any inconvenience caused. DOI of original article: 10.1016/j.jallcom.2021.160418.
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