Catalysis Science & Technology
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2020
·Vol. 10
·期 6
·1941-1951
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IF 5.721
Shaohua Chen,Hui Li,Yu Hao,Rui Chen,Tiehong Chen
A series of porous Mn-based oxides (mullite SmMn2O5, perovskite SmMnO3, spinel Mn3O4 and bixbyite Mn2O3) were systematically prepared and applied in ethanol and toluene catalytic oxidation. Among them, SmMn2O5 exhibited the highest catalytic activity, the best hydrothermal stability and the highest durability. Due to the different compositions and structures of the catalysts, the surface composition, Mn-valence state, reduction properties, and adsorption and desorption behavior of oxygen and ethanol were different as characterized by XPS, H2-TPR, O2-TPD and ethanol-TPD measurements. Based on the characterization results, the relationship between the catalyst structure (crystal and electronic structure) and catalytic activity was discussed in terms of their crystal field configurations and structures of the energy bands. The superior activity of SmMn2O5 could be attributed to dz2 orbital occupancy near the Fermi level determined by the Mn3+-centered pyramidal field, as well as the existence of a Mn3+–Mn3+ dimeric structure, which is critical for C–C bond cleavage.
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Journal of Energy Chemistry
·
2020
·
IF 7.216
Jia Sun,Lei Du,Baoyu Sun,Guokang Han,Yulin Ma,Jiajun Wang,Hua Huo,Pengjian Zuo,Chunyu Du,Geping Yin
ABO 3 -type perovskite oxides (e.g., LaCoO 3 ) with flexible and adjustable A- and B-sites are ideal model catalysts to unravel the relationship between the electronic structure and electrocatalytic activity (e.g., oxygen reduction/evolution reactions, ORR/OER). It has been well understood in our recent work that the secondary metal dopant at B-site (e.g., Mn in LaMn x Co 1 −x O 3 ) can regulate the electronic structure and improve the ORR/OER activity. In this work, the Mn-Ni pairs are employed as the dual dopant in LaMn x Ni y Co z O 3 ( x + y + z = 1) catalysts toward bifunctional ORR and OER. The structure–property relationships between the triple metal B-site (Mn, Ni and Co) and the electrochemical performance are particularly investigated. Compared to the individual Mn doping (e.g., LaMnCoO 3 (Mn:Co = 1:3) catalyst), the dual Mn-Ni doping significantly improves the ORR mass activity@0.8 V by 1.54 times; meanwhile, the OER overpotential@10 mA cm −2 is reduced from 420 to 370 mV, and the OER current density at 1.55 V is increased by 2.43 times. Reasonably, the potential gap between E ORR @-1 mA cm −2 and E OER @10 mA cm −2 is achieved as only 0.76 V by using the optimal LaMn x Ni y Co z O 3 ( x : y : z = 1:2:3) catalyst. It is revealed that the dual Mn-Ni dopant efficiently optimizes electron structures of the LaMnNiCoO 3 (1:2:3) catalyst, which not only decreases the e g orbital electron number, but also modulates the O 2p-band closer to the Femi level, accounting for the enhanced bifunctional activity.
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Nature Communications
·
2021
·Vol. 12
·期 1
·1-10
·
IF 14.919
Sayed Mahmoud,Xu Feiyan,Kuang Panyong,Low Jingxiang,Wang Shengyao,Zhang Liuyang,Yu Jiaguo
Solar conversion of CO 2 into energy-rich products is one of the sustainable solutions to lessen the global energy shortage and environmental crisis. Pitifully, it is still challenging to attain reliable and affordable CO 2 conversion. Herein, we demonstrate a facile one-pot approach to design core-triple shell Mn, C-codoped ZnO hollow spheres as efficient photocatalysts for CO 2 reduction. The Mn ions, with switchable valence states, function as “ionized cocatalyst” to promote the CO 2 adsorption and light harvesting of the system. Besides, they can capture photogenerated electrons from the conduction band of ZnO and provide the electrons for CO 2 reduction. This process is continuous due to the switchable valence states of Mn ions. Benefiting from such unique features, the prepared photocatalysts demonstrated fairly good CO 2 conversion performance. This work is endeavoured to shed light on the role of ionized cocatalyst towards sustainable energy production.
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PubMed
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ELECTROCHEMISTRY COMMUNICATIONS
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2021
·
IF 4.724
Lin Tang,Jinliu Wei,Zhixiong Cai,Feiming Li,Maosheng Zhang,Xiaomei Chen,Xi Chen
The electrochemical behavior and consequent luminescence properties of Mn-doped CsPbCl 3 perovskite (Mn:CsPbCl 3 ) nanocrystals (NCs) were investigated by cyclic voltammetry (CV) and electrochemiluminescence (ECL) measurements. Mn:CsPbCl 3 NCs could be electrochemically injected with electrons or holes at different potentials to produce ECL through both annihilation and coreactant routes. Importantly, it has been found that the ECL involving the coreactant could originate from two pathways: energy recombination at the surface, and energy transfer from the excited CsPbCl 3 host to the dopant center, producing emission via Mn d - d transition, which is different from the photoluminescence (PL) of Mn:CsPbCl 3 NCs alone, which contains dual emissions from both the host and the dopant.
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CHEMOSPHERE
·
2021
·
IF 7.086
Jian Cheng,Yirui Xie,Ying Wei,Dongrun Xie,Wenbo Sun,Ying Zhang,Menghong Li,Jiutao An
Dielectric barrier discharge (DBD) plasma coupled with Fe–Mn doped AC (Fe–Mn/AC) was used to enhance the degradation of tetracycline hydrochloride (TCH) wastewater. Fe–Mn/AC catalysts with different Fe/Mn molar ratios were prepared by hydrothermal method, and the physical and chemical properties of the samples were explored by different characterization techniques, including XRD, SEM , TEM and XPS. The results showed that the combination of DBD with Fe 2 –Mn 1 /AC system had the highest effect, and the degradation efficiency of TCH could reach 98.8 % after 15 min treatment, which was 25.5 % higher than that of DBD-only. With the increase of discharge voltage and catalyst dosage, the degradation efficiency of TCH promoted. And initial pH had little effect on the degradation of TCH. In the combined system, the Fe 2 –Mn 1 /AC catalyst could retain an excellent stability and reusability. The addition of dimethyl sulfoxide (DMSO) showed that ·OH participated in the TCH degradation. The generated O 3 might be catalyzed by Fe–Mn/AC catalyst to produce more ·OH. And more H 2 O 2 was produced in DBD-only system than that in DBD-catalytic system. Nine main degradation intermediate products in the combined system were detected by HPLC-MS, and three possible degradation pathways were proposed.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2021
·
IF 8.128
Yueyue He,Shuo Wang,Haiyan Zhang,Xin Chen,Jin Li,Huiyuan Xu,Yanhui Zhang,KangHui Hu,Genpin Lv,Yan Meng,Wei Xiang
Li-rich disordered rock-salt cathode (DRX) materials with advantage of low cost, long cycle life, nature abundant resource and high power and energy density attracted a great deal of scholarly attention. However, the poor cycle stability and the unclear realization of cation and anion redox activity in low-cost element system have severely hindered the construction of high-performance DRX. Herein, a promising class of Ti-Mn based cathode materials Li 1.25 Mn 0.25 Nb 0.25 Ti 0.25 O 2 and Li 1.25 Mn 0.25 Ti 0.5 O 1.75 F 0.25 were designed and successfully synthesized to construct high energy density DRX and investigate the effect of fluorination on cation and anion redox activity. The results show that both fluoridized and unfluoridized DRX possess a similar structure ( Fm -3 m), but distinctly different charge/discharge profiles. The fluoridized cathode shows high initial charge/discharge capacity of 317.3/283.9 mAh g −1 , specific energy density of 1370.4/735.5 Wh kg −1 and stable capacity retention with a discharge capacity of 202.6 mAh g −1 after 20 cycles at 20 mA g −1 . Combining relevant spectroscopic results and HRTEM images, we revealed that the excellent cyclability of Li 1.25 Mn 0.25 Ti 0.5 O 1.75 F 0.25 is rooted in the weakened adverse effects of moderated oxygen redox and the reduced Jahn–Teller distortion effect resulting from Mn 3+ , endowing the fluoridized DRX with better structural stability and larger Mn 2+ /Mn 4+ reservoir. The strategy of constructing low cost oxyfluoride and the understanding of the mechanism of fluorination induced cation and anion redox activity would provide reference for the development of high-performance DRX materials.
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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2019
·
IF 3.375
Siqian Zhang,Cheng Zhang,Qiang Wang,Wha-Seung Ahn
A series of ZSM-5 catalysts were synthesized using fly ash from power plants and red mud from aluminum production in different weight ratios. The ZSM-5 was subsequently coimpregnated with Co and Mn and tested for the low-temperature selective catalytic reduction of NOx by NH3 (NH3-SCR). These catalysts were characterized by XRD, N2-adsorption isotherms, SEM, XPS, and H2-TPR. Among all the prepared catalysts, 5 wt % Co 10 wt % Mn/ZSM-5 had shown the best catalytic activity, with 98.8% conversion of NOx and 90.7% selectivity toward N2 at 150 °C. This is comparable to the performance of a similar ZSM-5 catalyst prepared using chemical reagents. The high ratio of Mn4+/(Mn4+ + Mn3+ + Mn2+) in the catalyst improved the NOx conversion, whereas the moderate redox property imparted by Co3+ led to high N2 selectivity. This catalyst also showed strong resistance against poisoning in 100 ppm SO2 and 5% H2O. This work demonstrates that effective NOx removal treatment with high N2 selectivity and sufficient stability for either cement plants or incinerators can be achieved by using a porous catalyst/support material produced from industrial solid wastes.
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Advances in Materials Science and Engineering
·
2019
·
IF 1.399
Zhuo Yao,Dianli Qu,Yuxiang Guo,Yujing Yang,Hong Huang
Novel catalysts with high activity for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures are highly demanded. In this study, mixed-node metal-organic frameworks (MOFs), e.g. Mn@CuBTC with controlled Mn composition in Cu3(BTC)2, were fabricated using postsynthetic exchange method and their structural characteristics and catalytic performances for NH3-SCR reaction were assessed. A series of analyses in terms of structure, surface morphology, texture, and chemical state determined that Mn ions were successfully incorporated into the Cu3(BTC)2 crystal lattice as well as adsorbed on the walls of nanopores in the framework. The pore sizes can be finely tuned in the presence of Mn ions in the cages, which significantly suppressed water adsorption. The NH3-SCR activity of Mn@CuBTC exhibited nearly 100% NOx conversion rate in the temperature range (230–260°C). The superior NH3-SCR performance is attributed to the proper pore sizes, reduced water content, and the synergistic effect between manganese and copper ions in the MOF structure, which enhanced NH3 bound to the active Lewis sites.
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RSC Advances
·
2019
·Vol. 9
·期 67
·39315-39322
·
IF 3.049
Chang Liu,Jing Lin,Wei Zhai,Zhikai Wen,Xin He,Mengmeng Yu,Yang Huang,Zhonglu Guo,Chao Yu,Chengchun Tang
Doping metal ions in inorganic halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) endows the NCs with unique optical characteristics, and has thus attracted immense attention. However, controllable synthesis of high-quality doped perovskite NCs with tunable morphology still remains challenging. Here, we report a facile, effective and unified strategy for the controllable synthesis of Mn-doped CsPbCl3 quantum dots (QDs) and nanoplatelets (NPLs) via a single-step solvothermal method. The incorporation of Mn2+ into CsPbCl3 NCs introduces new broad photoluminescence (PL) emission from Mn2+ while maintaining the structure of host CsPbCl3 NCs nearly intact. The PL intensity, emission peak position and size of the NCs can be accurately adjusted by altering the experimental parameters such as Mn-to-Pb feed ratio and reaction time. Especially, by changing the amount of ligands, Mn-doped CsPbCl3 QDs, NPLs or their mixtures can be obtained. Both of the Mn-doped QDs and NPLs exhibit a size-dependent quantum confinement effect, which is confirmed by the relationship between the size of NCs and the exciton emission peaks. The solvothermal reaction condition plays an important role for the precise control of the structure, morphology and PL properties of the Mn-doped NCs. The as-prepared Mn-doped CsPbCl3 NPLs with thickness down to ∼2 nm exhibit a PL quantum yield (PLQY) of more than 22%. This work introduces a new strategy for the controllable synthesis of Mn-doped perovskite NCs, which provides ideas for the in-depth study of the dope-and-grow process and can be extended to approaches of doping other metal ions.
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APPLIED CATALYSIS B-ENVIRONMENTAL
·
2019
·
IF 14.229
Ling Zhang,Yiquan Xie,Yiwen Jiang,Yaobin Li,Chunying Wang,Shichao Han,Huimin Luan,Xiangju Meng,Feng-Shou Xiao
Catalytic combustion at low temperature has been considered as an effective route for removal of indoor HCHO pollutant, and conventional catalysts are supported noble metal nanoparticles, which are costly for wide applications. Solution of this issue is to use relatively low metal catalysts. Herein, we report that Mn-promoted Ag catalyst supported on pure silica Beta zeolite with a good hydrophobicity is very active for catalytic combustion of HCHO. By optimizing the loadings of Ag and Mn, it is found that 10 wt% Ag with 8 wt% Mn (10 %Ag8 %Mn/Beta-Si) exhibits highest activity, giving the complete HCHO conversion at around 45 °C, which steadily outperform the temperatures (70–145 °C) for full oxidation of HCHO reported previously. The choice of Ag loading with 10 wt.% is due to the highest exposed surface of Ag sites, and the use of Mn loading with 8 wt% is assigned to the balance of density and mobility for active oxygen species in the catalysts. The strategy combining the hydrophobic supports with optimized active oxygen species might offer an alternative way to develop highly efficient heterogeneous catalysts for the removal of air pollutants in the future.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2019
·
IF 4.084
Huiming Li,Yang Wang,Wei Zhu,Zhongbin Zhuang
Searching for low-cost electrocatalysts with high activity towards the hydrogen evolution reaction (HER) is of great significance to enable large-scale hydrogen production via water electrolysis . In this study, by using inverse spinel MFe 2 O 4 (M = Mn, Fe, Co, Cu) nanoparticles (NPs) as the precursors, monodisperse bimetallic phosphide M-Fe-P NPs/C with hollow structures were readily obtained by a gas-solid annealing method. These hollow phosphide NPs displayed excellent HER activity in an acidic medium with a low loading amount of 0.2 mg cm −2 . In particular, the Co–Fe–P NPs/C shows highest HER activity that only requiring an overpotential of 97 mV to retain a current density of 10 mA cm −2 . A volcano relation between activity and incorporated elements was revealed. Incorporation of cation with high electronegativity stabilized the FeP active centres, while phase segregation resulted in the loss of activity for Cu–Fe–P NPs/C.
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CHEMICAL ENGINEERING JOURNAL
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2019
·
IF 8.355
Zhen Zhang,Jiang Wu,Bin Li,Huibin Xu,Dongjing Liu
Zeolite (ZSM-5), as a kind of carbon-free sorbent or catalyst, has been widely applied in many fields due to its big surface area, good chemical and thermal stability, and excellent adsorption performance. In this study, Mn-Fe modified ZSM-5 are synthesized via sol-gel approach and employed for elemental mercury (Hg 0 ) removal from simulated flue gas at low temperature. The results show that pure ZSM-5 shows poor mercury capture ability with Hg 0 removal efficiency of ~8.5–18.8% at 100–300 °C. Mn or Fe modification can both efficiently enhance the Hg 0 removal efficiency of the ZSM-5. The sorbent with Mn/Fe molar ratio of 1:2 exhibits the optimal mercury capture ability with the highest Hg 0 removal efficiency near 100% at temperatures of 200 and 250 °C due to the significant synergy effect between Mn 2 O 3 and Fe 2 O 3 . The presence of NO has a negligible effect on the Hg 0 removal performance of Mn/ZSM-5 and Mn1Fe2/ZSM-5, while the existence of SO 2 considerably degrades the Hg 0 capture performance of Mn/ZSM-5 owing to competing adsorption and side reactions. Fe addition can protect Mn active sites from SO 2 poisoning and thereby enhancing the SO 2 resistance of Mn/ZSM-5 to some extent.
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