Anodes and Sodium‐Free Cathodes in Sodium Ion Batteries

The increase in electricity generation poses growing demands on energy storage systems, thus offering a chance for the success of the reliable and cost‐effective energy storage technologies. Sodium ion batteries are emerging as such a technology, which is however not yet mature enough to enter the market. At the crux of building practical sodium ion batteries is the development of electrode materials that promise sufficient cost‐ and performance‐competitiveness. As such, herein, all typical sodium storage materials are discussed, considering their fabrication methods and sodiation mechanisms in detail. A comprehensive cross‐literature and cross‐material comparison, which also includes the related thermodynamic analysis of their sodiation products, is also provided. The review focusses particularly on anodes and sodium‐free cathodes, as they both play the role of the acceptor rather than the donor of sodium ions in their operation in batteries; their difference lies in the (de‐)sodiation voltage. In the discussion, special attention is paid to contradictory observations and interpretations in contemporary sodium ion battery research, since debates on these controversies are likely to fuel future sodium battery research.     

Optimizing the electrode size and arrangement in a microbial electrolysis cell

This study investigates the influence of anode and cathode size and arrangement on hydrogen production in a membrane-less flat-plate microbial electrolysis cell (MEC). Protein measurements were used to evaluate microbial density in the carbon felt anode. The protein concentration was observed to significantly decrease with the increase in distance from the anode-cathode interface. Cathode placement on both sides of the carbon felt anode was found to increase the current, but also led to increased losses of hydrogen to hydrogenotrophic activity leading to methane production. Overall, the best performance was obtained in the flat-plate MEC with a two-layer 10 mm thick carbon felt anode and a single gas-diffusion cathode sandwiched between the anode and the hydrogen collection compartments.     

High Fill Factor Polymer Solar Cells Incorporating a Low Temperature Solution Processed WO3 Hole Extraction Layer

We demonstrate solution‐processed tungsten trioxide (WO₃) incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) with active layers comprising either poly(3‐hexylthiophene) (P3HT) or poly[(4,4'‐bis(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐(4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole)‐5,50‐diyl] (Si‐PCPDTBT) mixed with a fullerene derivative. The WO₃ layers are deposited from an alcohol‐based, surfactant‐free nanoparticle solution. A short, low‐temperature (80 °C) annealing is sufficient to result in fully functional films without the need for an oxygen‐plasma treatment. This allows the application of the WO₃ buffer layer in normal as well as inverted architecture solar cells. Normal architecture devices based on WO₃ HELs show comparable performance to the PEDOT:PSS reference devices with slightly better fill factors and open circuit voltages. Very high shunt resistances (over 1 MΩ cm²) and excellent diode rectification underline the charge selectivity of the solution‐processed WO₃ layers.     

Exploiting High‐Performance Anode through Tuning the Character of Chemical Bonds for Li‐Ion Batteries and Capacitors

A high‐performance anode material, MnNCN, is synthesized through a facile and low‐cost method. The relationship between electrochemical properties and chemical composition is explored on the scientific considerations that can provide an insight on designing expected materials. MnNCN with the long bonding length of 2.262 Å in Mn? N and weak electronegativity of 3.04 Pauling units in N leads to a lower charge/discharge potential than that of MnO owing to the character of chemical bonds transformed to covalent dominating from ionic dominating in MnO. Covalent character increases the ratio of sharing electrons that decreases the migration energy of electrons in electrochemical reaction, which enhances the reactive reversibility and stability of electrode material. MnNCN delivered a reversibly specific capacity of 385 mA h g^?1 at 5 A g^?1 in a Li‐ion half cell. Besides, a Li‐ion hybrid capacitor with a high voltage of 4 V presents energy and power densities of respective 103 Wh kg^?1 and 8533 W kg^?1 and cycles at 5 A g^?1 without detectable degradation after 5000 cycles.     

Na‐Mn‐O Nanocrystals as a High Capacity and Long Life Anode Material for Li‐Ion Batteries

Searching for a new material to build the next‐generation rechargeable lithium‐ion batteries (LIBs) with high electrochemical performance is urgently required. Owing to the low‐cost, non‐toxicity, and high‐safety, the family of manganese oxide including the Na‐Mn‐O system is regarded as one of the most promising electrode materials for LIBs. Herein, a new strategy is carried out to prepare a highly porous and electrochemically active Na_0.55Mn₂O₄·1.5H₂O (SMOH) compound. As an anode material, the Na‐Mn‐O nanocrystal material dispersed within a carbon matrix manifests a high reversible capacity of 1015.5 mA h g^?1 at a current density of 0.1 A g^?1. Remarkably, a considerable capability of 546.8 mA h g^?1 remains even after 2000 discharge/charge cycles at the higher current density of 4 A g^?1, indicating a splendid cyclability. The exceptional electrochemical properties allow SMOH to be a promising anode material toward LIBs.     

沉积型海底微生物燃料电池构建及其影响因素研究

海底微生物燃料电池具有底物丰富、可长期运行、维护成本低和环境友好等特点,具有很好的研究价值和广阔的发展前景。但由于其低的功率密度输出和长期运行的不稳定性,使海底微生物燃料电池尚未得到广泛地实际应用。选取海底沉积泥用于实验室构建的海底微生物燃料电池装置中,比较了在不同阳极材料、阴阳极面积比、阳极修饰、阳极泥下深度条件下海底微生物燃料电池的功率密度输出及其电化学性能,得出最佳的海底微生物燃料电池阳极材料为碳毡;阴极及电极最佳面积比为1∶1;最佳阳极修饰为氨水浸渍;最佳阳极泥下深度为2 cm。     

Microbial population and functional dynamics associated with surface potential and carbon metabolism

Microbial extracellular electron transfer (EET) to solid surfaces is an important reaction for metal reduction occurring in various anoxic environments. However, it is challenging to accurately characterize EET-active microbial communities and each member''s contribution to EET reactions because of changes in composition and concentrations of electron donors and solid-phase acceptors. Here, we used bioelectrochemical systems to systematically evaluate the synergistic effects of carbon source and surface redox potential on EET-active microbial community development, metabolic networks and overall electron transfer rates. The results indicate that faster biocatalytic rates were observed under electropositive electrode surface potential conditions, and under fatty acid-fed conditions. Temporal 16S rRNA-based microbial community analyses showed that Geobacter phylotypes were highly diverse and apparently dependent on surface potentials. The well-known electrogenic microbes affiliated with the Geobacter metallireducens clade were associated with lower surface potentials and less current generation, whereas Geobacter subsurface clades 1 and 2 were associated with higher surface potentials and greater current generation. An association was also observed between specific fermentative phylotypes and Geobacter phylotypes at specific surface potentials. When sugars were present, Tolumonas and Aeromonas phylotypes were preferentially associated with lower surface potentials, whereas Lactococcus phylotypes were found to be closely associated with Geobacter subsurface clades 1 and 2 phylotypes under higher surface potential conditions. Collectively, these results suggest that surface potentials provide a strong selective pressure, at the species and strain level, for both solid surface respirators and fermentative microbes throughout the EET-active community development.     

Hydrogen consumption in microbial electrochemical systems (MXCs): The role of homo-acetogenic bacteria

Homo-acetogens in the anode of a microbial electrolysis cell (MEC) fed with H₂ as sole electron donor allowed current densities similar to acetate-fed biofilm anodes (∼10 A/m²). Evidence for homo-acetogens included accumulation of acetate at high concentrations (up to 18 mM) in the anode compartment; detection of formate, a known intermediate during reductive acetogenesis by the acetyl-CoA pathway; and detection of formyl tetrahydrofolate synthetase (FTHFS) genes by quantitative real-time PCR. Current production and acetate accumulation increased in parallel in batch and continuous mode, while both values decreased simultaneously at short hydraulic retention times (1 h) in the anode compartment, which limited suspended homo-acetogens. Acetate produced by homo-acetogens accounted for about 88% of the current density of 10 A/m², but the current density was sustained at 4 A/m² at short hydraulic retention time because of a robust partnership of homo-acetogens and anode respiring bacteria (ARB) in the biofilm anode.