查看更多>>摘要：? 2022 Elsevier B.V.Development of highly efficient, durable and cost-effective catalysts for the hydrazine electrooxidation reaction (HzOR) is the key to successful implementation of direct hydrazine fuel cell (DHFC) as a commercially viable power source for vehicular or mobile applications. We herein report the fabrication of a Ni-foam-supported bicontinuous nanoporous Ni-Fe alloy using a hydrothermal method in combination with reductive calcination. The thus-prepared Ni-Fe/NF catalyst shows high activity, good stability and a close to 100% selectivity for the complete electrooxidation of hydrazine following the four-electron pathway, and its overall catalytic performance is comparable to the best level of HzOR catalysts. Our study demonstrates that alloying Ni with Fe could significantly improve the HzOR activity and meanwhile inhibit the non-faradaic hydrazine decomposition. Interestingly, the cheapest Fe appears more effective than many other transition metals in improving the catalytic performance of Ni-based HzOR catalysts.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, a novel NaLa(WO4)2/g-C3N4 photocatalyst with Z-scheme heterojunction was synthesized for the first time, and the photocatalytic purification of NOx was used as an evaluation method of its activity. The structure was analyzed in depth by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and other characterization methods. NaLa(WO4)2 and g-C3N4 have obvious interfaces and successfully constructed a Z-scheme heterojunction structure. The combination of photogenerated electrons on the conduction band (CB) of NaLa(WO4)2 with holes on the valence band (VB) of g-C3N4 leads to the accumulation of the remaining holes and electrons on the VB of NaLa(WO4)2 and CB of g-C3N4, and finally realizes the effective separation of photogenerated carriers and maintains the high redox ability of the catalyst. The NaLa(WO4)2/g-C3N4 composite catalyst has a highest NO purification rate of 47.18%, which is 16.51% higher than pure g-C3N4. Moreover, the In-situ DRIFTS monitors the reaction intermediates and final products of NO on the NaLa(WO4)2/g-C3N4 heterojunction surface under visible light irradiation, and provides the corresponding reaction equations. This work provides a new type of photocatalyst that is easy to prepare and highly active, as well as a low-cost photocatalytic treatment technology to remove NO in the environment.
查看更多>>摘要：? 2022 Elsevier B.V.Semiconductor photocatalysts, especially semiconductor heterojunctions, have great development potential in the field of photocatalysis. SnO2/g-C3N4 heterojunction has shown excellent photocatalytic performance rather than single SnO2 or g-C3N4, particularly for visible-light-driven photocatalysis. In this review, the synthesis methods of SnO2/g-C3N4 heterojunction are summarized. Then, the modification strategies of morphology control, defect introduction and multiple structural optimization strategies are highlighted. Morever, the possible mechanisms and applications in environment remediation and energy conversion of SnO2/g-C3N4 heterojunction are discussed. Finally, the challenges and perspectives of SnO2/g-C3N4 heterojunction are also proposed.
查看更多>>摘要：? 2022 Elsevier B.V.Iron (III) transition metal MFeOPO4@C (M: Co, Ni) oxyphosphates were synthesized using a solid-state reaction. The electrochemical properties of MFeOPO4@C were evaluated versus Li+/Li using two different binders (PVDF and CMC) in the voltage range 0.01–3.0 V. These phosphates show similar electrochemical profiles for both binders. They deliver a high discharge capacity during the first cycle around 755 mA h g?1 and 661 mA h g?1 for CoFeOPO4@C and 735 mA h g?1 and 789 mA h g?1 for NiFeOPO4@C when using PVDF and CMC binders, respectively. In our previous work, the electrochemical mechanism of MFeOPO4@C was investigated using in situ synchrotron XRD and X–ray absorption spectroscopy (XAS) revealing an irreversible amorphization of the crystal structure and the formation of new products at the end of discharge (Fe0, M0, Li2O, and Li3PO4). Moreover, XAS measurements showed that both transition metals M and Fe are active during the discharge/charge process. Our previous hypotheses suggested the oxidation of metallic iron to only divalent iron Fe2+ during charge. However, 57Fe M?ssbauer spectroscopy study reported here in this paper demonstrated that Fe3+ is partially reduced to Fe2+ and Fe0 in the first stages of lithiation, and then totally reduced to metallic iron by the end of discharge. Furthermore, when charging MFeOPO4@C against Li+/Li, 57Fe M?ssbauer spectroscopy technique surprisingly proved that iron is re-oxidized to + 2 and + 3. Therefore, the new data using 57Fe M?ssbauer spectroscopy has revealed insightful findings on the electronic changes of Fe upon the first lithiation/ delithiation.
查看更多>>摘要：? 2022 Elsevier B.V.Ni-Al-Cr intermetallic compounds are candidate at extreme environment due to their excellent oxidation resistance at high temperature, and the oxidation resistance of Ni-Al-Cr alloy system has been studied extensively. However, the research on oxidation resistance mechanism of porous Ni-Al-Cr intermetallic compounds is still not deep. In our work, porous Ni-Al-Cr intermetallic compounds were synthesized by thermal explosion, and the oxidation resistance of porous Ni-Al-Cr system was mainly investigated. The results indicate that Cr promotes the formation of highly protective continuous Al2O3 layer, increasing the oxidation resistance at 900 °C of porous Ni-Al-Cr. After oxidation at 900 °C for 120 h, the minimum mass gain of Ni-Al-Cr products is only 6.96%.
查看更多>>摘要：? 2022 Elsevier B.V.The development of high response, low detection limit and low-cost acetone sensors remains a great challenge so far. In this work, the high-performance acetone sensors based on Au nanoparticles (NPs)-loaded SnO2 porous nanosheets were successfully synthesized via metal-organic frameworks (MOFs) template method, which synthesis method is facile and meets the requirements of large-scale production. The acetone sensing characteristics of pristine SnO2 and Au-SnO2-based sensors are investigated. The optimized Au-SnO2-based sensor exhibits high response to acetone (Ra/Rg = 18.2 @100 ppm at 240 °C) with high selectivity and fast response/recovery time compared with that of pristine SnO2. Importantly, a fully reversible resistance signal with a low acetone concentration (1 ppm) can be detected, and the theoretical detection limit of the sensor is as low as 40 ppb. Finally, the enhanced acetone sensing performance of the Au-SnO2 sensor can be attributed to the increased specific surface area and chemically adsorbed oxygen, as well as the formation of Schottky junction between the Au and SnO2 interfaces.
查看更多>>摘要：? 2022 Elsevier B.V.The combination of chemical immobilization and accelerated conversion has been certificated as the most effective method to inhibit the shuttle effect. However, it remains challenging to clarify the electrochemical reduction pathways under the action of the catalyst. Here, the nickel phosphide nanosphere with reduced graphene oxide (Ni2P/rGO) as a bifunctional catalyst is proposed to anchor and catalyze the conversion of polysulfides. With a robust porous structure, the high specific surface area as well as the preponderant electrical conductivity, Ni2P/rGO can increase the active sites significantly and accelerate effectively the electron/ion transport, indicative of the accelerated conversion kinetics of polysulfides. Besides, Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical impedance spectroscopy (EIS) spectra at different discharge depths were used to analyze the sulfur reduction pathways under different catalysts, suggesting that Ni2P/rGO effectively enhances the kinetics of reduction reaction and reduces the energy barrier of the end products (Li2S) nucleation. Given these, upon a high sulfur loading of 5.3 mg cm?2, the Ni2P/rGO based electrode delivers a high area capacity of 4.067 mAh cm?2 at 0.2 C with excellent stability. This work provides an idea for studying the discharge mechanism of Li-S batteries.
查看更多>>摘要：? 2022 Elsevier B.V.Microparticles of Ni45.7Mn36.6In13.5Co4.2 have been prepared by means of different grinding methods (hand-grinding, cryo-milling, planetary ball-milling) followed by annealing treatments in order to recover the original martensitic transition and magnetic properties. A rapid reduction of particle size down to the micrometers has been obtained after few hours of milling, as it results from morphological analyses. Milling temperature, time, and medium strongly impact on the degree of induced stresses and particles aggregation, significantly changing the morphology, crystal structure and magnetic properties. It was found that both magnetic and magneto-structural phase transitions can be recovered by high-temperature annealing treatments (T > 1000 K). Time and temperature of the treatment have been optimized in relation to the disorder introduced by the milling process, which depends on its energy and duration. In general, our results show the strong dependence of the magneto-structural properties of the NiMnInCo compound on microstructural features, atomic order and chemical homogeneity, that imposes a careful selection and improvement of the preparation route.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, stannite, Cu2FeSnS4 (CFTS), absorber films were obtained by electrodeposition on Molybdenum-coated soda-lime substrates, followed by sulfurization treatment at certain temperatures in the 400–550 °C range. The purposes of this work were to control the manufacturing of CFTS films with good stoichiometry, high crystallinity and to study the annealing temperature impact on CFTS films properties. The X-ray diffraction and the Raman spectroscopy measurement distinguished the CFTS phase formation, with a presence of SnS2 secondary phase. The energy dispersive spectroscopy results reveal compositional differences between samples as well as the in-depth gradients. The photoluminescence emission band around 1.35–1.40 eV is slightly below the direct bandgap inferred from the conventional spectroscopy (diffuse reflectance). X-ray photoelectron spectroscopy results indicate clearly a high amount of Sn on the surface. The Conversion Electron M?ssbauer unveiled the presence of Fe in the chalcogenide unit cell. The electrochemical characteristics of the synthesized films are also given.
查看更多>>摘要：? 2022 Elsevier B.V.To improve the utilization rate of the precious metal, ruthenium, TiO2 nanospheres containing oxygen vacancies are grown on the surface of layered Ti3C2, and superfine Ru nanoparticles are fixed on the surface of TiO2 nanospheres via hydrogen reduction of a Ru precursor. The presence of titanium in a low oxidation state is verified by X-ray photoelectron spectroscopy, thus confirming the existence of oxygen vacancies. Spherical aberration transmission electron microscopy studies indicate the dispersion of uniform Ru nanoparticles (average diameter: ~2 nm) on TiO2, and the existence of a part of Ru in the form of single atoms. The catalyst with 0.33 wt% Ru loading exhibits the best catalytic performance in the hydrolysis of NaBH4 (NaBH4 hydrolysis rate at 303 K is 60 L·min?1·gRu?1). Further, the catalyst performs well even after five cycles of use.
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