Ramesh Kakarla

Highly flexible conductive fabrics with hierarchically nanostructured amorphous nickel tungsten tetraoxide for enhanced electrochemical energy storage

Amorphous nickel tungsten tetraoxide (NiWO4) nanostructures (NSs) were successfully synthesized on a flexible conductive fabric (CF) using a facile onestep electrochemical deposition (ED) method. With an applied external cathodic voltage (–1.8 V for 15 min), the amorphous NiWO4 NSs with burl-like morphologies adhered well on the seed-coated CF substrate. The burl-like amorphous NiWO4 NSs on CF (NiWO4 NSs/CF) are employed as a flexible and binder-free electrode for pseudocapacitors, which exhibit remarkable electrochemical properties with high specific capacitance (1,190.2 F/g at 2 A/g), excellent cyclic stability (92% at 10 A/g), and good rate capability (765.7 F/g at 20 A/g) in 1 M KOH electrolyte solution. The superior electrochemical properties can be ascribed to the hierarchical structure and large specific surface area of the burl-like amorphous NiWO4 NSs/CF. This cost-effective facile method for the synthesis of metal tungsten tetraoxide nanomaterials on a flexible CF could be promising for advanced electronic and energy storage device applications.

Microalgae Scenedesmus obliquus as renewable biomass feedstock for electricity generation in microbial fuel cells （MFCs）

Renewable algae biomass, Scenedesmus obliquus, was used as substrate for generating electricity in two chamber microbial fuel cells (MFCs). From polarization test, maximum power density with pretreated algal biomass was 102 mW·m−2 (951 mW·m−3) at current generation of 276 mA·m−2. The individual electrode potential as a function of current generation suggested that anodic oxidation process of algae substrate had limitation for high current generation in MFC. Total chemical oxygen demand (TCOD) reduction of 74% was obtained when initial TCOD concentration was 534 mg ·L−1 for 150 h of operation. The main organic compounds of algae oriented biomass were lactate and acetate, which were mainly used for electricity generation. Other byproducts such as propionate and butyrate were formed at a negligible amount. Electrochemical Impedance Spectroscopy (EIS) analysis pinpointed the charge transfer resistance (112 Ω) of anode electrode, and the exchange current density of anode electrode was 1214 nA·cm−2.

Enhanced performance of an air-cathode microbial fuel cell with oxygen supply from an externally connected algal bioreactor.

An algae bioreactor (ABR) was externally connected to air-cathode microbial fuel cells (MFCs) to increase power generation by supplying a high amount of oxygen to cathode electrode. The MFC with oxygen fed from ABR produced maximum cell voltage and cathode potential at a fixed loading of 459 mV and 10 mV, respectively. During polarization analysis, the MFC displayed a maximum power density of 0.63 W/m(2) (at 2.06 A/m(2)) using 39.2% O2 from ABR, which was approximately 30% higher compared with use of atmospheric air (0.44 W/m(2), 20.8% O2,). The cyclic voltammogram analysis exhibited a higher reduction current of -137 mA with 46.5% O2 compared to atmospheric air (-115 mA). Oxygen supply by algae bioreactor to air-cathode MFC could also maintain better MFC performance in long term operation by minimizing cathode potential drop over time.

The performance and long-term stability of low-cost separators in single-chamber bottle-type microbial fuel cells

ABSTRACT This study evaluates long-term stability of low-cost separators in single-chamber bottle-type microbial fuel cells with domestic wastewater. Low-cost separators tested in this study were nonwoven fabrics (NWF) of polypropylene (PP80, PP100), textile fabrics of polyphenylene sulfide (PPS), sulfonated polyphenylene sulfide (SPPS), and cellulose esters. NWF PP80 separator generated the highest power density of 280 mW/m2, which was higher than with ion-exchange membranes (cation exchange membrane; CEM = 271 mW/m2, cation exchange membrane; CMI = 196 mW/m2, Nafion = 260 mW/m2). MFC operations with other size-selective separators such as SPPS, PPS, and cellulose esters exhibited power densities of 261, 231, and 250 mW/m2, respectively. During a 280-day operation, initial power density of PP80 (278 mW/m2) was decreased to 257 mW/m2, but this decrease was smaller than with others (Nafion: 265–230 mW/m2; PP100: 220–126 mW/m2). The anode potential of around −430 mV did not change much with all separators in the long-term operation, but the initial cathode potential gradually decreased. Fouling analysis suggested that the presence of carbonaceous substance on Nafion and PP80 after 280 days of operation and Nafion was subject to be more biofouling.

Determination of Microbial Growth by Protein Assay in an Air-Cathode Single Chamber Microbial Fuel Cell

Microbial fuel cells (MFCs) have gathered attention as a novel bioenergy technology to simultaneously treat wastewater with less sludge production than the conventional activated sludge system. In two different operations of the MFC and aerobic process, microbial growth was determined by the protein assay method and their biomass yields using real wastewater were compared. The biomass yield on the anode electrode of the MFC was 0.02 g-COD-cell/g- COD-substrate and the anolyte planktonic biomass was 0.14 g-COD-cell/g-COD-substrate. An MFC without anode electrode resulted in the biomass yield of 0.07 ± 0.03 g-COD-cell/g-COD-substrate, suggesting that oxygen diffusion from the cathode possibly supported the microbial growth. In a comparative test, the biomass yield under aerobic environment was 0.46 ± 0.07 g-COD-cell/g-COD-substrate, which was about 3 times higher than the total biomass value in the MFC operation.

Basic Principles of Microbial Fuel Cell: Technical Challenges and Economic Feasibility

Water and energy securities are emerging as increasingly important and vital issues for today’s world. Therefore, the field of wastewater management and alternative energy is one of the most unexplored fields of Biotechnology and Science. Microbial fuel cell (MFC) is emerging as a modern wastewater treatment technology which converts chemical energy stored in the bonds of organic matter present in wastewater directly into electricity using electrogenic bacteria as a catalyst, without causing environmental pollution. In this chapter, the technical know-how of MFC and biocatalyst has been depicted. A thorough understanding of the fundamental principles of microbial fuel cells would help to perceive new aspects of bioenergy conversions and how such systems could be integrated with the present energy generation systems to maximize the energy recovery. In this respect, MFCs show promise to treat wastewater with simultaneous production of renewable energy. In this chapter, the theories underlying the electron transfer mechanisms, the biochemistry and the microbiology involved, and the material characteristics of anode, cathode, and the separator have been clearly described. This chapter highlights the major factors involved toward the improvement bioelectricity production processes. Advance in the design of MFC Technology and the economy of the process are also included.

Physicochemical Parameters Governing Microbial Fuel Cell Performance

Microbial fuel cell (MFC) performance has been dramatically improved by optimizing physicochemical parameters, especially in the early period of MFC research, for MFC practical applications. The enhancement in power output of MFC can be dependent on several physical and chemical parameters such as electrode material and morphology, catalyst on electrode, reactor design, membrane/separator, temperature, pH, electrolyte conductivity, and types of oxidants and substrates (fuels). The optimized conditions of physical and chemical parameters can enhance performance of MFC by decreasing internal resistance which is the sum of over potentials at the anode and cathode chambers and the separator part, and by increasing Columbic efficiencies. The effects of these parameters on MFC performance are discussed below in details.

Algae—The Potential Future Fuel: Challenges and Prospects

Algae are single or multicellular photosynthetic organisms that can fix the atmospheric carbon into valuable lipids, proteins, carbohydrates, and fats. These algae are also capable of growing vigorously in different habitats from freshwater to brackish water environments and wastewater streams with nutrient uptake ability. These features make the algae themselves uniquely important in biofuel generation and wastewater treatment process along with CO2 sequestrations without competing with food crop land. The algae can also be used as a substrate for various biofuel generations, bioethanol, bio-butanol, hydrogen, methane, and many commercially valuable products. The applicability and renewability of algal fuel are most promising for the future biotechnological applications. Optimization of algal growth conditions and harvesting technology with desired biofuel generations at low processing cost can make the algae as one of the best sources of energy for future generations. Genetically modified algae which are capable to grow rapidly with generating high cellular lipids and carbohydrate content can be crucial for future energy demand.