Data_Sheet_1_Microbially Induced Mineralization of Layered Mn Oxides Electroactive in Li Batteries.docx

Nanoparticles produced by bacteria, fungi, or plants generally have physicochemical properties such as size, shape, crystalline structure, magnetic properties, and stability which are difficult to obtain by chemical synthesis. For instance, Mn(II)-oxidizing organisms promote the biomineralization of manganese oxides with specific textures under ambient conditions. Controlling their crystallinity and texture may offer environmentally relevant routes of Mn oxide synthesis with potential technological applications, e.g., for energy storage. However, whereas the electrochemical activity of synthetic (abiotic) Mn oxides has been extensively studied, the electroactivity of Mn biominerals has been seldom investigated yet. Here we evaluated the electroactivity of biologically induced biominerals produced by the Mn(II)-oxidizer bacteria Pseudomonas putida strain MnB1. For this purpose, we explored the mechanisms of Mn biomineralization, including the kinetics of Mn(II) oxidation, under different conditions. Manganese speciation, biomineral structure, and texture as well as organic matter content were determined by a combination of X-ray diffraction, electron and X-ray microscopies, and thermogravimetric analyses coupled to mass spectrometry. Our results evidence the formation of an organic–inorganic composite material and a competition between the enzymatic (biotic) oxidation of Mn(II) to Mn(IV) yielding MnO2 birnessite and the abiotic formation of Mn(III), of which the ratio depends on oxygenation levels and activity of the bacteria. We reveal that a subtle control over the conditions of the microbial environment orients the birnessite to Mn(III)-phases ratio and the porosity of the assembly, which both strongly impact the bulk electroactivity of the composite biomineral. The electrochemical properties were tested in lithium battery configuration and exhibit very appealing performances (voltage, capacity, reversibility, and power capability), thanks to the specific texture resulting from the microbially driven synthesis route. Given that such electroactive Mn biominerals are widespread in the environment, our study opens an alternative route for the synthesis of performing electrode materials under environment-friendly conditions.

由细菌、真菌或植物合成的纳米颗粒（nanoparticles）通常具备尺寸、形貌、晶体结构、磁学性能及稳定性等理化特性，而这些特性往往难以通过化学合成手段获取。例如，Mn(II)氧化微生物可在常温常压条件下，促进具有特定形貌的氧化锰发生生物矿化（biomineralization）。调控其结晶度与形貌，有望开辟环境友好型氧化锰合成路径，在储能等领域具备潜在技术应用价值。然而，尽管合成（非生物成因，abiotic）氧化锰的电化学活性已得到广泛研究，但Mn基生物矿化产物的电活性却鲜有报道。本研究针对Mn(II)氧化细菌恶臭假单胞菌（Pseudomonas putida）菌株MnB1诱导生成的生物矿化产物的电活性展开评估。为此，本研究探究了不同条件下Mn生物矿化的机制，包括Mn(II)氧化反应动力学。通过X射线衍射、电子与X射线显微成像技术以及热重-质谱联用分析，对锰的赋存形态、生物矿化产物的结构与形貌，以及有机质含量进行了表征。研究结果表明，体系中生成了有机-无机复合材料，且存在两种反应的竞争：一是酶促（生物成因，biotic）途径将Mn(II)氧化为Mn(IV)，生成水钠锰矿（birnessite，MnO₂）；二是非生物途径生成Mn(III)，二者的占比取决于溶氧水平与细菌活性。本研究发现，对微生物培养环境条件进行精细调控，可以改变水钠锰矿与Mn(III)物相的占比，以及聚集体的孔隙率，而这两个因素均会显著影响复合生物矿化产物的整体电活性。以锂电池构型对该复合产物的电化学性能进行测试，结果显示其展现出优异的性能（电压、容量、可逆性及倍率性能），这得益于微生物介导合成路径所赋予的独特形貌结构。鉴于此类电活性Mn基生物矿化产物在环境中分布广泛，本研究为环境友好型高性能电极材料的合成开辟了一条新路径。