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排序方式: 共有5381条查询结果,搜索用时 46 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(64):27508-27515
Customizing catalysts from the electronic structure, such as spin state, is an effective but challenging strategy for oxygen evolution reaction (OER). Herein, an ultrafine Co–Fe material highly dispersed on nitrogen carbide matrix is fabricated by coordination polymer and self-templating method to scrutinize the impact of spin state of Co on OER through Fe doping. The optimized catalyst shows boosted OER performance, which only requires overpotential of 333 mV at 10 mA cm?2, outperforming other control samples and commercial RuO2. The elevated local spin states of Co by Fe doping lead to charge transfer acceleration and fast generation of oxygenated intermediates, which is proved to account for the OER elevation. In addition, the long-term stability of Co–Fe material is guaranteed by the strong coordination of Co/Fe to the melamine-formaldehyde resin, which is used to adsorb metal ions, contributing to the high dispersion of active sites during the OER process. 相似文献
2.
《Ceramics International》2022,48(6):8297-8305
Pure and Sn/Fe co-doped (0.2 at.% Sn and 0.6 at.% Fe, 0.6 at.% Sn and 0.2 at.% Fe, 1.0 at.% Sn and 1.0 at.% Fe) TiO2 nanoparticles were synthesized via a sol-gel method and subsequently calcined at different temperatures. Furthermore, the particles were analyzed by TG-DSC, XRD, TEM, HRTEM, EDS, SAED and UV–Vis for investigating the influences of dopant and calcination temperature on the thermal effect, composition, morphology, energy band gap (Eg) and the degradation efficiency of methyl orange (MO) under various light irradiations respectively. Results indicated that Sn/Fe co-doping inhibited the crystallization transformation from anatase to rutile phase of TiO2 and decreased the Eg. The increased calcination temperature and Sn/Fe co-doped effect brought about the abnormal grain growth of TiO2 nanoparticles. 0.6 at.% Sn/0.2 at.% Fe and 1.0 at.% Sn/1.0 at.% Fe co-doped TiO2 nanoparticles presented better photocatalytic performance than pure and 0.2 at.% Sn/0.6 at.% Fe co-doped TiO2 nanoparticles under visible light irradiation mainly due to the decreased Eg. On the contrary, 0.2 at.% Sn and 0.6 at.% Fe co-doped TiO2 nanoparticles calcined at 650 °C showed the most excellent photocatalytic performance under UV light irradiation, which was about twice as large as that of pure TiO2 possibly due to the formed hybrid structure of anatase and rutile phase as well as the h+-mediated decomposition pathway. 相似文献
3.
The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. 相似文献
4.
《International Journal of Hydrogen Energy》2021,46(74):36811-36823
Nitrogen-doped transition metal materials display promising potential as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Fe/N co-doped three-dimensional (3D) porous graphene (FeN-3D-PG) is prepared via a template method using sodium alginate as the carbon source and low polymerization degree melamine resin as the nitrogen source. The low polymerization degree melamine resin can form complexes with Fe3+ in the aqueous solution and further forms high density Fe-Nx active sites during pyrolysis. Meanwhile, the formed 3D porous structure efficiently promotes the uniform distribution of Fe-Nx active sites. The FeN-3D-PG catalyst exhibits pH-independent ORR activity. For OER, the catalyst possesses a low over potential (370 mV at 10 mA cm−2) in alkaline electrolyte. The Zn-air batteries (ZABs) using FeN-3D-PG as cathode exhibits a power density up to 212 mW cm−2, a high specific capacity of 651 mAh g−1, and the charge-discharge stability of 80 h. This work provides new sight to transition metal materials based ZABs with excellent performance. 相似文献
5.
《International Journal of Hydrogen Energy》2021,46(58):29896-29904
Water oxidation is a key reaction for water splitting. The decomposition of Fe-based-molecular structures toward Fe-based oxides is a promising method for oxygen-evolution reaction (OER) through water oxidation. The decomposition of Fe-based-molecular structures method results in a slow decomposition of precatalysts and forms Fe oxide-based catalysts. In this study, the Fe species formed through the decomposition of a dinuclear Fe(III) complex under OER is investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and the electrochemical method. In addition, using Ni(OH)2, a new approach is reported for detecting trace Fe species on the electrode surface. The resulting Fe oxide-based catalyst shows a catalytic current with an onset of 621 mV overpotential and the Tafel slope of 113.7 mV/decade at pH 11 in a buffer phosphate. 相似文献
6.
《中国有色金属学会会刊》2021,31(12):3800-3813
The Fe−Ni−TiO2 nanocomposite coatings were electrodeposited by pulse frequency variation. The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies. By increasing the pulse frequency from 10 to 500 Hz, the iron and TiO2 nanoparticles contentswere increased in expense of nickel content. XRD patterns showed that by increasing the frequency to 500 Hz, an enhancement ofBCC phase was observed and the grain size of deposits was reduced to 35 nm. The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO2 nanoparticles into the Fe−Ni matrix (5.13 wt.%). Moreover, the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased. 相似文献
7.
Sankalp Kota Louisiane Verger Varun Natu Maxim Sokol Michel W. Barsoum 《Journal of the American Ceramic Society》2021,104(2):733-739
The thermal stability and decomposition mechanisms of Fe2AlB2 powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N2) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe2AlB2 and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as-synthesized Fe2AlB2 powders are treated in dilute HCl to dissolve impurity phases, decomposition in N2 atmospheres occurs readily above 1200 K. The decomposition reaction involves β-FeB precipitation and the liberated Al atoms reacting with the ambient N2 to form AlN. Under Ar environments, HCl-treated Fe2AlB2 powders decompose and precipitate β-FeB, by the out-diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N2 atmospheres revealed that Fe2AlB2 was more thermally stable when synthesized from lab-synthesized, instead of commercially available, FeB precursors and when the HCl treatment was avoided. The effects of the various factors on the decomposition temperature and decomposition mechanisms are discussed herein. 相似文献
8.
MIL-53(Fe)/polyaniline (PANI) composite was prepared by in situ depositing PANI on the surface of MIL-53(Fe) and their catalytic performances on the simultaneous removal of RhB and Cr(VI) were investigated. The elimination efficiency of both RhB and Cr(VI) reached more than 98% under pH=2 where hydrochloric acid and citric acid were used to adjust the pH. The results indicated that MIL-53(Fe)/PANI revealed an obvious pH response to the degradation of RhB, while citric acid promoted the Cr(VI) photoreduction. UV-Vis spectra, EIS, and photocurrent response experiments showed that MIL-53(Fe)/PANI had a better light response and carrier migration ability than MIL-53(Fe). The transient absorption spectra also exhibited that the lifetimes of photo-generated carriers were prolonged after the conductive polymer deposition on the MIL-53(Fe) surface. Scavenger experiments demonstrated that the main active species were ·O2- and OH. Combined with activity evaluation results, and the possible photocatalytic mechanism of MIL-53(Fe)/PANI on RhB oxidation and Cr(VI) reduction was proposed. The addition of conductive polymer can effectively improve the light response of the catalyst under acidic conditions, and meanwhile citric acid also provided a new mediation for the synergistic degradation of multiple pollutants. Good activity and stability of the catalysts made the scale-up purification of acid water feasible under UV-Vis light. 相似文献
9.
《International Journal of Hydrogen Energy》2021,46(59):30334-30343
The development of microbial fuel cells (MFCs) into a new type of carbon-neutral wastewater treatment technology requires efficient and low-cost oxygen reduction reaction catalysts in air cathodes. The use of raw soybean powder was investigated for synthesizing Fe–N–C ORR catalysts in a sacrificial SiO2 support method. ZnCl2 etching in the synthesis was found to facilitate the formation of hierarchical porous structures of Fe–N–C catalysts. Fe–N–C(1-1) catalyst synthesized with an optimal soybean/ZnCl2 mass ratio of 1:1 exhibited the highest ORR activity in air cathodes. The use of the obtained Fe–N–C(1-1) catalyst enables a maximum power production of ~0.480 mW cm−2 in MFCs, higher than commercial Pt/C (0.438 mW cm−2) with the same catalyst loading of 2 mg cm−2. Long-term MFC operations demonstrated that the Fe–N–C synthesized from raw soybean have high stability and toxic tolerance, indicating that abundant low cost soybean biomass is a potential material for ORR catalyst development in MFC applications. 相似文献
10.
Yan Luo Zeming Tang Guiqiang Cao Da Bi David P. Trudgeon Adeline Loh Xiaohong Li Qingxue Lai Yanyu Liang 《International Journal of Hydrogen Energy》2021,46(2):1997-2006
Atomically dispersed transition metals anchored on N-doped carbon have been successfully developed as promising electrocatalysts for acidic oxygen reduction reaction (ORR). Nonetheless, how to introduce and construct single-atomic active sites is still a big challenge. Herein, a novel concave dodecahedron catalyst of N-doped carbon (FeCuNC) with well confined atomically dispersed bivalent Fe sites was facilely developed via a Cu-assisted induced strategy. The obtained catalyst delivered outstanding ORR performance in 0.5 M H2SO4 media with a half-wave potential (E1/2) of 0.82 V (vs reversible hydrogen electrode, RHE), stemming from the highly active bivalent Fe-Nx sites with sufficient exposure and accessibility guaranteed by the high specific surface area and curved surface. This work provides a simple but efficient metal-assisted induced strategy to tune the configurations of atomically dispersed active sites as well as microscopy structures of carbon matrix to develop promising PGM-free catalysts for proton exchange membrane fuel cell (PEMFC) applications. 相似文献