CHEMICAL ENGINEERING JOURNAL
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2021
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IF 13.273
Chen Qiao,Zahid Usman,Tai Cao,Souleymen Rafai,Zhitao Wang,Youqi Zhu,Chuanbao Cao,Jiatao Zhang
High-valence Ni and Fe metal sites have demonstrated a crucial role in enhancing the catalytic performances of NiFe-LDH electrocatalysts in oxygen evolution reaction (OER). Although considerable OER catalytic performances achieved under high overpotential, the catalytic talent of NiFe-LDH electrocatalysts at low overpotential is rarely realized due to the absence of high-valence Ni and Fe sites. We herein report a surface engineering route to fabricate sulfated NiFe-LDH nanosheets via ion exchange strategy in sulfate-rich media. XPS results reveal a modified surface electronic structure with high-valence Ni and Fe after ion exchange reaction. Computational PDOS results suggest that computed d-band centers (ε d ) of Fe and Ni for sulfated NiFe-LDH show a significant downward shift resulting an increased valence of metal cation with orbital volume shrinkage. The high-valence Fe can facilitate a optimized multi-electron process of Ni center from [Ni II -OH] − /[Ni III -OH] − to Ni IV -OOH rather than Ni II /Ni III to Ni IV at low overpotential. The high-valence Ni can serve as the highly active center for O-O coupling during OER process. Combined with the synergetic action of high-valence Fe and Ni, the sulfated NiFe-LDH nanosheets exhibit much larger reaction kinetics and outstanding electrocatalytic activity on glassy carbon electrode (η 10 = 219 mV, η 50 = 288 mV) with a remarkable long-term stability.
研究领域:
材料科学
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电化学
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催化科学
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DOI
高影响因子
IONICS
·
2023
·Vol. 29
·期 7
·2853-2864
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IF 2.8
Wang Wenping,Zhao Zhiyi,Deng Jiayao,Lang Wei,Zhen Lipeng,Lu Huimin
The oxygen reduction reaction of the cathode in an Al-air battery plays a key role in the performance of the entire battery. Generally, Pt and its alloys are recognized as catalysts with high oxygen reduction catalytic performance, but their application is limited by the rare earth content and high cost. In this paper, α-MnO 2 nanotubes are prepared using a hydrothermal method and used as a template. Nano-Ni–Mn bimetallic oxides with different compositions are prepared with different NiO and α-MnO 2 ratios by calcination. The effects of morphology, phase, and Mn 3+ /Mn 4+ and Ni 3+ /Ni 2+ ratios on electrochemical performance and battery discharge performance are analyzed. The results show that the contents of α-MnO 2 and Ni 6 MnO 8 in NM-12 catalyst are low, and the molar ratio of Mn 3+ /Mn 4+ and Ni 3+ /Ni 2+ is high. Also, the specific surface area of NM-12 is relatively high. Finally, the catalyst prepared with a NiO to α-MnO 2 ratio of 1:2 shows better electrochemical catalytic performance and battery discharge performance that is comparable to that obtained for a commercial 20 wt% Pt/C catalyst.
研究领域:
材料科学
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电化学
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能源存储与转换
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NUCLEAR MATERIALS
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2014
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IF 2.016
Xin Wang,Kuo Jiang,Liang Zhou
Powders of (Nd 1− x Ce x ) 2 Zr 2 O 7+ y ( x = 0–1) with pyrochlore structure were prepared by sol-spray pyrolysis and subsequent graphite reduction at 1200 °C. The effects of cerium content on crystal structure, phase stability and microstructure of the (Nd 1− x Ce x ) 2 Zr 2 O 7+ y ( x = 0–1) inert matrix materials were studied. XRD and Raman results presented that all samples were in a single pyrochlore phase. XPS results indicated the cerium was in a single oxidation state of +4. After sintering at 1500 °C for 24 h in air, the sample of x = 1 underwent a phase segregation to Zr 1− x Ce x O 2 solid solutions of tetragonal, metastable tetragonal and cubic phases, the sample of x = 0.9 contained a few tetragonal phase in addition to fluorite phase, the samples of x = 0.5–0.8 had a single phase fluorite structure, the samples of x = 0–0.4 maintained the pyrochlore structure.
研究领域:
材料科学
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无机化学
✓ 已验证
产品关联
DOI
高影响因子
Processes
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2022
·Vol. 10
·期 12
·2562
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IF 3.352
Yuxi Gao,Baofang Jin,Xiaodong Wu,Zhenguo Li,Rui Ran,Duan Weng
Two Mn0.15Ce0.85O2−δmixed oxides were synthesized by a co-precipitation method using Mn(NO3)2and KMnO4as the manganese precursors, respectively. Structural analyses by X-ray powder diffraction and Raman spectroscopy reveal the formation of MnOx-CeO2solid solutions. The Mn0.15Ce0.85O2−δcatalyst prepared from the high-valent manganese precursor exhibits higher activity for the catalytic oxidation of NO. The advantage of KMnO4is related to the improved redox property of the catalyst as supported by H2temperature-programmed reduction (TPR) and O2temperature-programmed desorption (TPD). The Mn-Ce interactions create more Mn4+, Ce3+and oxygen vacancies on the KMnO4-synthesized mixed oxides based on the Raman and X-ray photoelectron spectra (XPS).Keywords:solid solutions;precursor;oxidation state;lattice defects;NO oxidation
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Advanced Energy and Sustainability Research
·
2023
·Vol. 4
·期 11
·2300056
·
IF 5.8
Wei Zhang,Tianyi Wang,Chuangwei Liu,Chongxiong Duan,Wei Xiong,Hao Li
Gold-based electrocatalysts are potential candidates for electrocatalytic nitrogen reduction reaction (e-NRR) application due to their high conductivity and low hydrogen evolution tendency. However, the role of nonmetallic Au surfaces is not widely studied. Herein, the self-assembly of gold nanoparticles confined in carbon felts (Au NPs@CFs) containing two different states of Au is reported, showing effective e-NRR performance. The effects of surfactant concentration on the morphology and electrochemical performance of the Au NPs are analyzed. X-ray photoelectron spectroscopy indicates two valence states of Au (Au 0 and Au 3+ ) in Au NPs@CFs. Interestingly, it is found that the e-NRR properties of Au NPs@CFs enhance with the increase of Au 3+ content. A typical sample Au NPs@CF-1.0 with the highest Au 3+ content exhibits the best e-NRR performance (NH 3 yield of 66.1 μg h −1 mg −1 cat. and Faradaic efficiency of 24.9% at −0.3 V vs reversible hydrogen electrode), which, in part due to the presence of Au 3+ , is conducive to nitrogen adsorption. Theoretical calculation results find that a stable Au 3+ surface can adsorb N 2 strongly, which in turn can lead to energetically favorable formation of ammonia. This study provides new insights into the relation between oxidation states and performance of gold-based electrocatalyst with high e-NRR performance.
研究领域:
材料科学
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电化学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materiomics
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2020
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IF 5.797
Qikai Li,Qing Zhou,Long Wen,Weishu Liu
Flexible polymer thermoelectric thin film attracts wide attentions because it is compatible with the wearable electronics and e-skin. Herein, we reported an enhanced thermoelectric power factor of PEDOT:PSS from around 1 μW m −1 K −2 to 117 μW m −1 K −2 and high substrate-free strain of 20% through synergistically tuning the ordering structure and the oxidation state. An ionic liquid (EMImTCM) was used to decouple the ionic interaction between PEDOT and PSS, rearranging the morphology of structure that significantly benefit the mechanical flexibility and the electrical conductivity. The addition of L-ascorbic acid was confirmed as effective dedoping additive of PEDOT polymer that changed the oxidation state and hence boosted the thermoelectric power factor without notable sacrifice of the mechanical flexibility. Moreover, the electrical conductivity of the corresponding film maintained electrically stable (Δ R/R 0 < 0.12%) under 1000 bending cycles which indicates the great bendability. Our work demonstrated the feasibility to controllably tailor the thermoelectric and mechanical performance of the PEDOT:PSS flexible polymer thermoelectric thin film.
研究领域:
材料科学
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能源技术
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
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2020
·
IF 16.683
Lihan Pan,Wen Shi,Tapas Sen,Lingzhi Wang,Jinlong Zhang
The role of high-valent Fe has rarely been explored in persulfate-based heterogeneous reaction. Herein, the existence of Fe(IV) is verified in a visible light-assisted FeTiO 3 /persulfate system using methyl phenyl sulfoxide as the probe. The FeTiO 3 /persulfate/light system is capable of selectively degrading aromatic compounds with lower ionization potentials including tetracycline and bisphenol A by photo-generated high-valent Fe(IV). The contributions from SO 4 ·- , · OH and 1 O 2 are excluded. The comparable efficiency in the dark requires higher dosages and suffers from a rapid deactivation. Based on XPS, Raman and EPR analyses, the poor dark activity is caused by the formation of a complex between in situ formed Fe(III) and SO 4 2- on the FeTiO 3 surface; this complex is, however, the key intermediate for Fe(IV) production under the light irradiation. This study reveals the long-ignored role of SO 4 2- as an abundant species in iron-based persulfate systems. We also call for re-evaluating the real oxidation mechanism in other persulfate-based reactions considering the different oxidation mechanisms of radicals and high-valent iron.
研究领域:
环境科学
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化学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
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2020
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IF 3.83
Yuqian Wang,Honghong Lei,Peng Jiang,Lin Liu,Kunyang Cui,Wenbin Cao
Mn-doped Ba 7 Al 2- x Mn x O 10+ y (0 ≤ x ≤ 0.7) samples with intense blue colors are successfully prepared by solid state reactions. With the increase of Mn content, the colors of compounds are tuned from cyan to ocean blue. FT-IR absorption spectrum and 27 Al NMR spectrum indicate that the structure contains a dominating portion of Al–O tetrahedral sites while a small number of Al–O octahedral sites may also exist. The oxidation state of Mn is proved to be +5. Based on all the analysis, the intense blue shades of the samples are proposed as the d-d transition of Mn 5+ ions in [AlO 4 ] tetrahedral sites.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
高影响因子
Molecular Catalysis
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2018
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IF 0
Jun Huang,He Huang,Licheng Liu,Hongtao Jiang
MnO x based catalysts exhibit excellent low-temperature activity in the selective catalytic reduction (SCR) of NO x by NH 3 . The effect of Mn oxidation state (chemical valence) on the NH 3 -SCR activity is an interesting topic and important for designing an active catalyst. This study aimed to clarify the intrinsic effect of Mn valence in NO-SCR reaction. For this purpose, the pure MnO x (MnO, Mn 3 O 4 , Mn 2 O 3 , MnO 2 ) and physical mixed 30% MnO x /TiO 2 catalysts, as well as three Mn/TiO 2 catalysts prepared by impregnation, were investigated for the low temperature NO-SCR with NH 3 in the presence of excess O 2 . The catalysts were characterized by N 2 adsorption, X-ray diffraction (XRD), X-ray Absorption Fine Structure (XAFS), and temperature programmed reduction of H 2 (H 2 -TPR) to probe the physical and chemical properties of catalysts. The MnO x with different chemical valence exhibited distinct intrinsic activity. The Mn 3 O 4 and MnO/TiO 2 showed the highest intrinsic activity (TOR) for the unsupported and supported catalysts, respectively. The MnO x species with low chemical valence (MnO, Mn 3 O 4 ) exhibited overall high intrinsic SCR activity (larger than 0.012 NO h −1 nm −2 MnOx ). The MnO x with different valence normally changed to higher oxidation state after physically mixed with TiO 2 . The content of MnO x species with different valence depended on their loading and Mn precursor, showing a totally different constitution. This work provides new insights into the Mn valence effect on the intrinsic activity for low-temperature SCR.
研究领域:
催化化学
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环境科学
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产品关联
DOI
CRYSTENGCOMM
·
2023
·Vol. 25
·期 15
·2271-2279
·
IF 3.1
Jingwen Hou,Bernard A. Goodman,Yuchen Lu,Qunyue Zhang,Bin Huang,Long Chen,Shoulei Xu,Wen Deng,Dingkang Xiong
Synthetic Ti-doped delafossite (CuFe1−xTixO2) was prepared by solid state reaction of Fe2O3, CuO and TiO2, and crystals were successfully prepared by the optical floating zone method using a modified experimental protocol that produced crystals in <10% of the time used in previous work. The effects of Ti on the microstructure and magnetic properties of CuFeO2 were investigated. The nonlinear change of cell size may be the result of Ti4+ reduction to Ti3+. However, the Fe oxidation state was not affected by Ti doping, although some oxidation of Cu+ to Cu2+ was observed with the highest Ti contents. The two characteristic magnetic transition temperatures of CuFeO2 occurred at 17 K (TN1) and 11 K (TN2) in the undoped crystal, and these increased to 51 K and 20 K, respectively, in the crystal with x = 0.007, although there was no major change in the two magnetic transition temperatures in crystals with other doping concentrations. In an applied magnetic field of 500 Oe, the magnetization of the x = 0.007 sample was 22 times that of CuFeO2, and its magnetization curve shows the coexistence of regions with ferrimagnetic and antiferromagnetic properties. Furthermore, magnetic hysteresis loops revealed that the saturation magnetization (M) of the sample x = 0.007 is 4.15 emu g−1, but at higher Ti concentrations the M–H curves returned to pairwise linear temperature dependence. Overall, crystals of synthetic delafossite with greatly affected magnetic properties can be prepared by doping with a limited range of Ti contents.
研究领域:
材料科学
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固体物理学
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产品关联
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2024
·
IF 6.3
Mingming Yu,Zhimin Gao,Wang Xie,Xiaochao Shi,Ousheng Zhang,Zhigang Shen,Lin Fang,Musu Ren,Jinliang Sun
The oxidation state of phosphorus has a great influence on the flame retardant action of its flame retardants. In this study, a reactive phosphorus-containing flame retardant (POG-DOPO) with both low and high phosphorus oxidation states is synthesised and incorporated into epoxy resin. The results show that the part in high oxidation state act mainly in the condensed phase and the part in low oxidation state act mainly in the gas phase. Furthermore, the flame retardant exhibits a synergistic flame retardant effect, resulting in a higher flame retardant efficiency than that of flame retardants with a single phosphorus oxidation state. Compared with unmodified epoxy resin, the peak heat release rate, total heat release rate and total smoke release of POG-DOPO modified epoxy resin with only 3wt% phosphorus are reduced by 70.9%, 51.2% and 55.7%, respectively. Its LOI increases to 31.8% and vertical combustion test achieves UL-94 V-0 rating. This study provides a strategy for the structural design of efficient phosphorus-based flame retardants.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2023
·
IF 16.5
Ning Zhang,Jiayi Du,Na Zhou,Depeng Wang,Di Bao,Haixia Zhong,Xinbo Zhang
Proton-exchange membrane water electrolysis, particularly driven by renewable electricity, is a sustainable strategy for green hydrogen production . However, developing highly active and stable electrocatalysts to accelerate the oxygen evolution reaction (OER) remains challenging. Herein, we introduce an effective strategy for constructing high-valence metal-doped IrO x with abundant oxygen vacancies, while simultaneously enhancing the catalytic activity and stability of the acidic OER. The synthesized Ta-doped IrO x (350-Ta@IrO x ) exhibits ultramicroscopic nanoparticle morphology and abundant surface oxygen vacancies, enabling a rapid OER process with a low overpotential of 223 mV at 10 mA cm -2 and 147.7 times higher mass activity (1207.4 A g Ir −1 ) than that of commercial IrO 2 at 1.55 V versus the reversible hydrogen electrode. More importantly, 350-Ta@IrO x affords excellent stability with insignificant potential degradation after 500 h of electrolysis at 10 mA cm 2 , originating from the low operating potential and suppressed dissolution and oxidation of oxygen vacancy active sites via Ta doping. Density functional theory calculations suggest that Ta doping and oxygen defect engineering are effective in facilitating the nucleophilic attack of water molecules, thereby accelerating the rate-determining step toward high catalytic OER activity on Ta-doped IrO x . We anticipate that this study will provide an effective method to obtain active and stable electrocatalysts via high-valence metal doping.
研究领域:
化学
·
材料科学
·
能源科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）