Birnessite Nanosheet Arrays with High K Content as a High‐Capacity and Ultrastable Cathode for K‐Ion Batteries

Potassium‐ion batteries (PIBs) are one of the emerging energy‐storage technologies due to the low cost of potassium and theoretically high energy density. However, the development of PIBs is hindered by the poor K⁺ transport kinetics and the structural instability of the cathode materials during K⁺ intercalation/deintercalation. In this work, birnessite nanosheet arrays with high K content (K_0.77MnO₂?0.23H₂O) are prepared by “hydrothermal potassiation” as a potential cathode for PIBs, demonstrating ultrahigh reversible specific capacity of about 134 mAh g^?1 at a current density of 100 mA g^?1, as well as great rate capability (77 mAh g^?1 at 1000 mA g^?1) and superior cycling stability (80.5% capacity retention after 1000 cycles at 1000 mA g^?1). With the introduction of adequate K⁺ ions in the interlayer, the K‐birnessite exhibits highly stabilized layered structure with highly reversible structure variation upon K⁺ intercalation/deintercalation. The practical feasibility of the K‐birnessite cathode in PIBs is further demonstrated by constructing full cells with a hard–soft composite carbon anode. This study highlights effective K⁺‐intercalation for birnessite to achieve superior K‐storage performance for PIBs, making it a general strategy for developing high‐performance cathodes in rechargeable batteries beyond lithium‐ion batteries.     

Iron and manganese oxides in Finnish ground water treatment plants

Large amounts of ochreous precipitates are formed on aeration of Fe containing Finnish ground waters during purification for drinking purposes. Sixty-four precipitates were characterized chemically and mineralogically. X-ray diffraction (XRD) indicated that the Fe-rich precipitates consist mainly of a poorly ordered ferrihydrite (5 Fe₂O₃ · 9 H₂O) which only has 2–3 of the 6 XRD lines characteristic of better ordered ferrihydrite. The surface area ranges between 325 and 433 m² g⁻¹ corresponding to a particle size of 5 nm. The ferrihydrites contain 3–7% Si strongly associated with the ferrihydrite as indicated by an i.r. absorption band at 960–975 cm⁻¹ which is associated to Fe-O-Si bonds. Si-containing ferrihydrite typically forms by rapid oxidation of ground waters with 1–23 mg 1⁻¹ Fe and 7–12 mg 1⁻¹ Si at pH 6–7. Very similar products formed in a simulation experiment in which artificial ground water with 20 mg 1⁻¹ Fe was oxidized in the presence of 12 mg 1⁻¹ Si. A1 < 4 mg 1⁻¹ Si lepidocrocite (γ-FeOOH) was formed showing that Si in the system prevents the formation of the more stable and better crystallized FeOOH forms. A transformation of 2-line ferrihydrite to better ordered ferrihydrite or goethite with time is indicated. The Mn-oxide birnessite was identified in black precipitates formed in one plant.     

Delamination of Birnessite MnO2 into Nanosheets as Anode Materials for Lithium Ion Batteries

水钠锰矿二氧化锰的剥离及所得纳米片的电化学性能

夏傲¹,宜珏¹,于婉茹¹,杨欣²,赵晨鹏¹

（1. 陕西科技大学材料科学与工程学院 陕西省无机材料绿色制备与功能化实验室,西安 710021;2. 陕西彩虹新材料有限公司,陕西 咸阳 712000）

摘要：本研究采用循环冷冻-溶融法成功剥离了水钠锰矿型二氧化锰从而获得MnO2纳米片。将氢型MnO2加入含有四甲基氢氧化铵水溶液的聚丙烯管中,待聚丙烯管密封后立即移入液氮中冷冻30 s,管中液体冻结后随即将该管移至70 ºC的恒温水浴中,30 min解冻后将聚丙烯管再次移入液氮中进行冷冻,如此反复循环70次。通过X射线衍射(XRD)和透射电子显微镜(TEM)对产物的物相和微观形貌进行了表征。XRD结果表明,氢型MnO2的层状结构已剥离,TEM结果表明产物形貌呈纳米片状。所制备的MnO2纳米片在电流密度1000 mA/g 下循环100次后比容量仍高达1040.6 mAh/g。

关键词：水钠锰矿型二氧化锰;纳米片;锂离子电池;比容量;液氮

     

Synthesis and structural characterization of copper incorporated manganese oxide OMS-2 materials synthesized via potassium birnessite

Metal ion incorporated tunnel structured manganese oxide OMS-2 has been recently exploited as potential materials in the field of heterogeneous catalysis Cryptomelane type copper incorporated manganese oxide OMS-2 type tunnel structured material has been synthesized by hydrothermal method using birnessite-containing potassium as a parent precursor instead of using birnessite containing sodium. Crystal structure and thermal stability of as synthesized materials are characterized by using XRD and TGA. Surface area and morphology of newly synthesized copper incorporated OMS-2 type materials have been studied by BET and SEM analyses.     

氧化石墨/水钠锰矿型锰氧化合物纳米复合材料的新合成法及其电化学性质

将水钠锰矿型锰氧化合物沉淀于剥离状态的氧化石墨层上，利用被锰氧化合物单层所包裹的氧化石墨的自配列，合成了一种新型氧化石墨-锰氧化合物隔层排列的纳米复合材料。测量了将得到的材料作为锂离子二次电池正极材料时的电化学性质，结果表明这种纳米复合材料具有比水钠锰矿型锰氧化合物更高的充放电再循环性。     

Pd负载型介孔ZrO2-TiO2复合材料的设计合成及其CO催化氧化性能研究

为了有效去除大气污染物中的CO,使用氧化还原法制备层状锰氧化物MnO_x-L,并用离子交换法制备了负载不同质量分数Fe的Fex/MnO_x-L催化剂.使用扫描电子显微镜（scanning electron microscope,SEM）、X射线衍射（X-ray diffraction,XRD）技术、比表面积测定（brunauer emmett teller,BET）、热重分析（thermogravimetric analysis,TGA）、氢气程序升温还原（hydrogen temperature-programmed reduction,H₂-TPR）、氧气程序升温脱附（oxygen temperature-programmed,O₂-TPD）、X射线光电子能谱（X-ray photoelectron spectroscopy,XPS）等技术表征催化剂形貌、结构及性能.层状锰氧化物MnO_x-L具有典型的八面体层状结构,Fe负载对催化剂结构影响不大,但对其理化性质产生了影响.Fe负载改变了催化剂的还原性及其表面的m（Fe²⁺）/m（Fe³⁺）和m（O_ads）/m（O_latt）比例,提高了样品的催化活性.在所有Fex/MnO_x-L样品中,Fe5/MnO_x-L具有最高的低温还原性、氧移动性,m（Fe²⁺）/m（Fe³⁺）及表面吸附氧最高.催化氧化CO反应中,Fe5/MnO_x-L具有最佳的催化活性（t₅₀=80℃和t₉₀=150℃）,这与Fe和MnO_x-L载体之间的相互作用有关.

     

层状Birnessite型锰氧化物国内外研究进展

综述了Birnessite型、负载型层状锰氧化物的结构特点、制备方法、应用现状等,重点介绍了各种制备方法的优缺点,并展望了层状锰氧化物研究的发展趋势。     

Curing of a polysulfide sealant with sodium birnessite

Sodium birnessite (Na₂MnMnO₁₃ · H₂O), a layered manganese(IV) oxide–based phase, gives a liquid polysulfide cure that is too rapid for normal application when added at 10 pph polysulfide. The curing behavior of sodium birnessite added as 5 pph, 4 pph, and as a 5 : 5 pph mixture with an inert natural manganese dioxide was compared with that of a readily available manganese‐based commercial curing agent. The rate of cure at 5 and 4 pph was slower than the commercial agent at 10 pph and led to products with lower tensile strength. The cure with the 5 : 5 pph mixture gave a more rapid reproducible cure than that of the commercial agent, making a product with a higher tensile strength and lower elongation, which indicates better curing and higher crosslinking. The improved performance of sodium birnessite as a curing agent is consistent with the presence of Mn²⁺ in the lattice, creating vacancies in the Mn⁴⁺ O²⁻ lattice and increasing the mobility of Mn⁴⁺ and its transport to the surface of the solid to oxidize the polysulfide. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1177–1181, 2000