Your article. Microbial Fuel Cells and Online. Microbial Electrolyzers FAST! by Abhijeet P. Borole More than 100,000 articles in all areas of electrochemistry and solid state icrobial fuel cells are electrochemical devices that use where vibrational energy is used to increase the rate of reaction, science and technology from the only nonprofit publisher in its field. microbes as catalysts instead of inorganic catalysts to electrocatalysis has a significant advantage, because voltage is drive the anodic and/or cathodic reactions to produce the driving force for reactions in addition to temperature, which electricity.1 The field of microbial fuel cells (MFCs) minimizes the energy losses to the environment, thereby improving was initially focused on wastewater treatment, but the conversion efficiency. Biocatalysis is another low temperature Mhas evolved into a much more diverse field of research called catalytic process that works at the molecular level by overcoming the Bioelectrochemical Systems (BES). Microbial electrolyzers or energy of activation via structural re-combination of reactants that microbial electrolysis cells (MECs) are a different manifestation self-assemble into catalytic sites. Combining electrocatalysis with of BES that generate hydrogen using less than half the voltage or biocatalysis in the bioelectrochemical approach employed in BES • ECS journals author choice open access. electrical energy needed for conventional water electrolysis. The results in a significant synergy, improving efficiency significantly. reduced electrical input is enabled by the chemical energy that comes This is because of the continuity of the electron flow from the substrate • Quality peer review. from organic or reduced inorganic substrates that serve as the feedstock to the product, afforded first, via the biocatalytic reaction, and then • for hydrogen production in MECs. Electrons are extracted from the by the electrocatalytic reaction, resulting in a continuous path within Continuous publication. substrates and converted into hydrogen at the cathode, operating the electrical circuit. This mechanism is supported by the relatively • High impact research in technical content at room temperature. The cathode catalysts can be metal-based or recent discovery of electrical communication between biological biological in nature. Figure 1 shows a generalized configuration of systems and electrodes. Biological nanowires have been identified to areas published daily. the BES. The versatility of the BES platform shown in the figure enable efficient electron conductance between inorganic substrates • illustrates the potential of this approach to produce not only electricity and organic or biological entities. Pili-based nanowires have been Focus journal issues. and hydrogen but also biofuels, chemicals and bioproducts. identified in Geobacter sulfurreducens and Shewanella oneidensis, • More than 80 years of up-to-the minute and which are capable of electron transfer from microbes to an anode.2,3 Electrocatalysis-Biocatalysis Synergy Direct interfacing of electron producers and electron sinks has given archival scientific content. rise to this high degree of efficiency evidenced in microbial fuel cells. • Leading-edge, accessible content platform. Fuel cells have set a high mark for energy efficiency among the Similarly, MECs also have high efficiency, shown by the generation various renewable energy production options that have evolved over of hydrogen from acetate using microbes at a Coulombic efficiency 4 • Free e-mail alerts and RSS feeds. the last few years. The high efficiency comes from the molecular above 90% and an overall energy efficiency as high as 82%. nature of electrocatalysis. In comparison to thermocatalysis, • Sample articles available at no charge. Relevance to Energy Production st • ECS members receive FREE ACCESS to 100 in the 21 Century articles each membership year. The field of BES has given rise to an increasing number of opportunities for collaborations between electrochemists, biologists, • Flexible subscription options available to Summer 2014 and engineers. This has brought together a unique opportunity for these three communities to work together and contribute to the advancement academic and corporate libraries and other VOL. 23, NO. 2 Summer 2014 of the field. MFCs originated as a potential solution to wastewater institutions. treatment a decade ago. Water has become an increasingly scarce IN THIS ISSUE 3 From the Editor: Working With Stuff commodity during the last decade. Zero-energy wastewater treatment 9 From the President: The Grandest Challenge of Them All 11 Orlando, Florida ECS Meeting Highlights is one vision for the scientists working in the area of BES development. 36 ECS Classics– Hall and Héroult and the Discovery of Aluminum Electrolysis This is one of the many components of the water-energy nexus issues 39 Tech Highlights 41 Twenty-Five Years of Scanning Electrochemical Microscopy 43 Studying Electrocatalytic that the USA is currently facing. Synergy of BES with biorefineries Activity Using Scanning Electrochemical Microscopy 47 Measuring Ions with Scanning Ion Conductance Microscopy has also been identified, with potential improvement in the efficiency 53 Electrochemistry at the Nanoscale: The Force Dimension 5 25 Years of 61 Functional Electron of conversion of biomass to energy. Hydrogen production has been Microscopy for Electrochemistry Research: From the Atomic to the Scanning Micro Scale pursued from various renewable sources including solar, wind power, VOL. 23, NO. 2 Electrochemical Microscopy and biomass, etc. Economically competitive production of renewable If you haven’t visited the hydrogen, however, has been a challenge. MECs offer a new, energy- efficient method for hydrogen production from biomass and waste. ECS Digital Library recently, The ability to produce hydrogen from waste and biomass hydrolysis www.ecsdl.org please do so today! products, namely sugars and organic acids has been demonstrated.6 Conversion of lignin-degradation products, phenolic compounds, and furan aldehydes at the bioanode has also been demonstrated.7 This opens the door to the possible conversion of essentially all components of biomass to hydrogen using MECs. Not an ECS member yet? Economic Considerations Start taking advantage of member benefits right now! Economic feasibility of BES can come from one of three ways. www.electrochem.org While the primary function of these systems is energy production, worthwhile benefits can be realized from their contribution to reduction in waste and/or production of clean water (Fig. 2). A current FIG. 1. Schematic of bioelectrochemical systems including MFCs and MECs. (continued on next page) The Electrochemical Society Interface • Fall 2015 • www.electrochem.org 55 Leading the world in electrochemistry and solid state science and technology for more than 110 years Borole (continued from previous page) Table I. Comparison of cost of hydrogen production.9,11 The costs reported in last column are based on 2003 $, except for MEC. 9,10 8,11 $/kg H2 EERE Literature 2011 Status 2015 Target Wind + Electrolysis 4.10 3.00 6.64 PV-Electrolysis 6.18a Clean Biomass gasification 2.20 2.10 4.63 Waste Water Biomass pyrolysis 3.80 Reduction Production Solar thermal NA 14.80 Photoelectrochemical cell NA 17.30 Photobiological NA 9.20 (2020 Target) Energy Nuclear thermal 1.63 Production splitting of water Natural gas reforming 2.00 2.10 1.03 Coal gasification 0.96 Microbial electrolysis NA 12.43b 5.40c Reforming of FIG. 2. Three potential benefits of BES technology contributing to economic bio-derived liquidsd feasibility. 1. Ethanol 6.60 5.90 density of 25 A/m2 has been suggested as a threshold for economic 2. Bio-oil aqueous phase12 31.84 3.00e feasibility of MFCs,8 possible with reduction in internal electrical (2017 Target) 2 resistance below 40 mΩ m . Electricity as a product from MFCs may a not by itself justify the costs of implementing these systems, however, Based on projected future technology. bDerived from [10]. A cost of $5.18 was deduced from the reported hydrogen removal of key contaminants or production/recycle of water at zero production cost of $12.43, which was for production of substrate via fermen- energy cost would warrant use of these systems. tation. The reported cost of electrodes for MEC ($300/m2, 2015 target set in Microbial electrolyzers, on the other hand, generate renewable the multi-year program plan developed by the FCTO),9 however, does not give hydrogen that is valued higher than electricity and thus have a estimated cost of hydrogen production. It assumes a hydrogen production rate greater potential to reach economic feasibility. A comparison of of 1 L-H2/L-reactor-day (2015 Target). MEC technology against other existing technologies for hydrogen cDerived from [8]. This is a projected cost using reduced cost of electrode production is shown in Table I. materials in the future. d Among the renewable energy technologies included in Table 1, For conversion of bio-derived liquids to hydrogen via steam reforming. MECs are observed to be a relatively cost competitive alternative, however this technology is nascent and significantly more effort is required to reduce the costs down to the $2/kg H2 set by the U.S. Electrochemical Methods to Study BES Department of Energy (DOE) (not including hydrogen storage and delivery costs). Specific cost reduction goals set by the DOE Fuel Techniques such as cyclic voltammetry and impedance Cell Technology Office