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Biological Fuel Cells: Cardinal Advances and Critical Challenges

2014; Wiley; Volume: 1; Issue: 11 Linguagem: Inglês

10.1002/celc.201402361

2196-0216

Plamen Atanassov, Mohamed Y. El‐Naggar, Serge Cosnier, Uwe Schröder,

Electrochemical Analysis and Applications

The always-young field of bioelectrochemistry has seen an unusual development: a move away from its comfortable analytical roots toward energy harvesting and power generation, as manifested by an explosion of projects, symposia and published papers. Wiley(-VCH) publications have provided a platform for this emerging trend by not only being the home for many of those individual breakthrough and developmental papers, but also by dedicating the pages of its well-established Electroanalysis for the first special issue on biological fuel cells (or biofuel cells)1 in 2010, a special issue on microbial fuel cells in ChemSusChem in 2012,2 and in 2014 publishing a book that is a compendium of the enzymatic fuel cell effort to date and another dedicated to implanting these biofuel cells in living organisms.3, 4 Now, this growing, exciting and captivating field is presenting itself on the pages of the special issue of one of the newest members of the Wiley family, ChemElectroChem. The guest-editors are among the most engaged contributors to this field, and you will find an authorship list that will both convince you of the depth of the questions asked and the breadth of the solutions suggested. We are very happy to present these 30+ original contributions and focused topical reviews that provide a snapshot of a burgeoning field so dynamic and explosive in ideas and, sometimes, controversy, that the only problem the guest-editors had, was how not to lose the momentum. We thank all the contributors for trusting this issue with their best work of 2014. It was an amazing experience to not hear a single “no” in the process of recruiting this “by invitation only” volume, but rather to only receive suggestions on who else should be invited as well. This speaks volumes of the sense of camaraderie, mutual respect and promotion of the best science in the field of electrochemistry of biological systems for energy conversion, harvesting and power generation. Biological fuel cells (BFCs) are usually understood as devices that utilize biological systems (enzymes, organelles, microorganisms or tissues) and their intrinsic catalytic activity for energy transformation reactions. As those processes are usually associated with ubiquitous fuels, available in the environment, both natural and anthropogenic, the practical application of the BFCs is often associated with energy harvesting. The two main classes of these devices are the enzymatic fuel cells (EFCs) and microbial fuel cells (MFCs) divided by the primary use of either isolated enzymes or living microorganisms as catalysts. A broader definition also includes an abiotic fuel cell (or specific electrodes) that are designed to function by converting biologically available fuel (biomass, components in cellular or intercellular fluids of a living organism), regardless of the active catalytic components. Such abiotic electrodes are usually combined in a hybrid device with a bio-electrode (enzymatic or microbial), or an abiotic cell is used for energy harvesting while implanted in living tissue. The full diversity of these approaches is captured in this special issue. The EFCs are predominantly associated with small/ miniature devices with relatively high power density output that can be designed as a bio-battery, either containing all their fuel in a compartment of the cell or as a flow-through, open system that utilizes an external fuel stream. Often EFCs share design concepts with electrochemical biosensors, with the principal difference being the spontaneity of the electrochemical reactions happening at the electrodes. EFCs, however, are used as self-powered sensors and/or logical devices that can be integrated as electrical actuators in complex systems. The critical drawback of the EFCs has always been the timespan of their operation, which is critically limited by the environmental stability of immobilized enzymes while operating in abiotic environments. This special issue addresses the issues of integration of enzymes and nanomaterials, both carbonaceous (carbon nanotubes, their composites or synthetic hierarchically structured carbons) and metallic nanoparticles. Special attention is paid to the state and modification of the electrode interface to facilitate the charge transfer between the enzyme and the electrode for co-factors, among them PQQ, FAD and NADH. The works presented here address the issues of fuel flexibility and design for utilization of complex fuels, such as monosaccharides, sugars, starches and others. The design solutions vary from laboratory test units and well-defined electrodes to practical prototypes suitable for in vivo implantation or environmental testing. Microbial fuel cells are usually much larger devices that have evolved from laboratory-scale experiments in power generation to complex devices for wastewater treatment or biocatalyzed electrolysis and other fuel generation. This journal issue includes work focusing on the mechanisms of charge transfer between the microorganism and the electrode interface, examining current hypotheses that involve redox shuttles, multiheme cytochromes, and different modes of charge transfer under different physiological conditions. These research questions are addressed using the classic model organisms Geobacter and Shewanella, while the methods used range from atomistically informed simulations of the electron transfer proteins to cyclic voltammetry, as well as directed evolution and synthetic biology with the goal of engineering microbes that possess the desired charge transfer properties. Beyond the traditional model systems, the issue also includes studies featuring hydrogen-evolving, phototrophic, and metal-oxidizing bacteria. In addition to fundamental studies of the charge transfer pathways, the complexity of microbial catalysts is investigated in studies geared towards understanding the organization of biofilms and the role of multiple microorganisms in energy harvesting and/or metabolic symbiosis with other biofilm colonists. Practical applications in hydrogen generation or water purification are also discussed, giving a positive outlook to a field that is just entering the first wave of pilot-scale deployments and commercial start-ups. The issue also provides a glance into a new field in microbial electrochemistry, called microbial electrosynthesis. Here, bacteria are used to catalyze electrosynthetic processes, such as the production of organic compounds from CO2, which widens the spectrum of potential applications of microbial electrochemistry from environmental technology towards biotechnology. Plamen Atanassov graduated from the University of Sofia specializing in Chemical Physics and Theoretical Chemistry. He joined the Bulgarian Academy of Sciences and became a Member of Technical Staff of its Central Laboratory of Electrochemical Power Sources (now the Institute for Electrochemistry and Power Systems). His initial work included materials solutions for metal–air batteries. He was a visiting scientist at the Frumkin’s Institute of Electrochemistry, Moscow, Russia studying bioelectrochemistry of enzymes and received a Ph.D. in Physical Chemistry/Electrochemistry. Dr. Atanassov moved to the United States in 1992 and later became a research faculty with the University of New Mexico. During the 1990s he was involved in development of several electrochemical biosensor technologies for biomedical, environmental, food safety and defense applications. In 1999 Plamen Atanassov joined Superior MicroPowders LLC (acquired later by Cabot Corp.) where he was a project leader in fuel cell electrocatalysts development that resulted in the introduction of spray pyrolysis for catalyst synthesis on an industrial scale. He returned to the University of New Mexico in 2000 as faculty member of the Chemical and Nuclear Engineering Department. In 2007 Dr. Atanassov founded the UNM Center for Emerging Energy Technologies. From January 2012 to December 2013 Dr. Atanassov was the Associate Dean for Research of the UNM School of Engineering. Currently Dr. Atanassov is a Distinguished Professor of Chemical and Biological Engineering and leads research programs in development of novel electrocatalysts: non-platinum electrocatalysts for fuel cells, nanostructured catalysts for oxidation of complex fuels, new materials and technologies for energy conversion and storage. Dr. Atanassov′s bioelectrocatalysis programs range from enzyme electrochemistry, enzymatic and microbial fuel cells to systems for biological and bio-inspired energy harvesting. His research is funded by NSF, DOD, DOE and industrial partners, among those Daihatsu Motor Co, Ballard Power Systems, AFCC, SFD Research Corp. and others. Moh El-Naggar (M.S. and Ph.D. from the California Institute of Technology) is an Assistant Professor of Physics and Biological Sciences at the University of Southern California. As a biophysicist, El-Naggar investigates energy conversion and charge transmission at the interface between living cells and synthetic surfaces. El-Naggar was awarded the USA Presidential Early Career Award for Scientists and Engineers (PECASE) in 2014. In 2012, he was named one of Popular Science Magazine′s “Brilliant 10”. His research efforts are funded by AFOSR, DOE, and NASA. Serge Cosnier is Research Director at the CNRS and head of the Department of Molecular Chemistry at the Grenoble Alpes University (France). He received his doctoral degree in Chemistry from the Toulouse University (1982) and was an Alexander von Humbold postdoctoral fellow. Cosnier’s activity is focused on biosensors, biofuel cells, electrogenerated polymers, molecular electrochemistry and carbon nanotubes. Since 2001, he is the President of the French Group of Bioelectrochemistry. In 2009 Dr. Cosnier received the Katsumi Niki Prize for Bioelectrochemistry from the International Society of Electrochemistry, where he was appointed as Fellow in 2010. He was elected to the Academia Europaea in 2013. Uwe Schröder holds the professorship for Sustainable Chemistry and Energy Research at the Technische Universität Braunschweig, Germany. His research emphasis is electrochemistry, comprising different aspects of electrochemical energy conversion and storage. For more than ten years, microbial fuel cells and microbial electrochemistry have been his major area of work.