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Green Energy Applications of Carbon Nanotubes
Published in Soney C. George, Jacob Philip, Ann Rose Abraham, A. K. Haghi, Carbon Nanotubes for Energy and Environmental Applications, 2023
Except solar energy, hydrogen is a clean energy source when comparing with conventional fuel. Hydrogen fuel has been taken into account as a good approach for the developing technologies of green energy.65,66 Microbial electrolysis cells (MECs) are the new technology for hydrogen production and it is developed on the basis of MFCs. The hydrogen will produce through microbial electrolysis from organic waste. The organic materials will be oxidized by microorganisms and produced carbon dioxide. These processes will also result in the release of electrons from the oxidative reactions to the anode and transferring protons into the solution. With an additional supply of voltage to the cathode will result in a proton–electron interaction along with the production of hydrogen. The CNTs can be incorporated with biocathode in the MEC. In particular, polymer MWCNT composite can be employed as the composition of a biocathode for biohydrogen yield in a single-chamber MEC.67,68
Microbial Electrochemical Technologies for Fuel Cell Devices
Published in Mu Naushad, Saravanan Rajendran, Abdullah M. Al-Enizi, New Technologies for Electrochemical Applications, 2020
S. V. Sheen Mers, K. Sathish-Kumar, L. A. Sánchez‐Olmos, M. Sánchez-Cardenas, Felipe Caballero-Briones
A microbial electrolysis cell (MEC) is a modified form of MFCs where the main motive is the conversion of organic matter into value-added products like hydrogen, methane, acetate, and hydrogen peroxide from which electricity can be produced indirectly (Kumar et al. 2017). The difference between a microbial fuel cell and a microbial electrolytic cell is depicted graphically in Figure 5.7. Of these value-added products, hydrogen evolution is more desirable as it can be directly used for electricity production. Usually, in MFCs, the protons produced due to anode reaction are reduced in the cathodic compartment to produce hydrogen gas. For the reduction of protons, platinum is found to be highly active and is generally used as the cathode. Several challenges are there regarding the production of hydrogen from such a setup. The methanogenic bacteria compete with the electroactive bacteria that are present within the wastewater. The methanogenic bacteria consume the produced hydrogen from the cathode and convert them into methane. Loss of hydrogen yield will also happen when no membrane is used during the cell operation. The reduced hydrogen gas reaches the anode, and again, it will be converted to protons (Rozendal et al. 2008;Patil et al. 2015). Moreover, various studies show that activated carbon is a suitable alternative for the high-cost cathode material, Pt (Ge et al. 2015).
A research challenge vision regarding management of agricultural waste in a circular bio-based economy
Published in Critical Reviews in Environmental Science and Technology, 2018
Nathalie Gontard, Ulf Sonesson, Morten Birkved, Mauro Majone, David Bolzonella, Annamaria Celli, Hélène Angellier-Coussy, Guang-Way Jang, Anne Verniquet, Jan Broeze, Burkhard Schaer, Ana Paula Batista, András Sebok
Microbial electrolysis cells (MEC) is an emerging eco-efficient and low-cost technology which can generate biomethane or hydrogen from organic material by applying an external electric potential or a current. In a MEC, “electro-active” microorganisms, or electro-trophes, are attached to the anode and oxidise organic waste substrates to carbon dioxide by using the electrodic material (usually graphite based) as final electron acceptor of their metabolism. The electrons produced by the anodic oxidation reaction, flowing across the external circuit, are used to (bio)catalyse the production of reduced target molecules such as H2, CH3COOH or CH4 (Zhen et al., 2017; Zeppilli et al., 2016a). This enables coupling waste treatment with the generation of energy carriers and chemicals. If a MEC is configured for “electromethanogenesis”, i.e. for reduction of CO2 to CH4 catalysed by electro-trophes attached to the cathode, the wastewater treatment (COD) oxidation in the anode can be coupled with the biogas upgrading to biomethane (Figure 3) (Villano et al., 2013; Blasco-Gómez et al., 2017).
The mechanism and application of bidirectional extracellular electron transport in the field of energy and environment
Published in Critical Reviews in Environmental Science and Technology, 2021
Qingqing Xie, Yue Lu, Lin Tang, Guangming Zeng, Zhaohui Yang, Changzheng Fan, Jingjing Wang, Siavash Atashgahi
MFC involving the two model systems has been shown to be effective in treatment of a small amount of real wastewater in a lab-scale or even pilot-scale MFC reactor. For example, pure culture of S. oneidensis were successfully inoculated to construct a well-established MFC for substrate degradation and current production from agriculture and domestic wastewater (Nimje et al., 2012). Likewise, the treatment of metals-laden wastewater has been shown to achieve concurrent organic pollutants oxidation, heavy metals reduction, and electricity generation (Gupta et al., 2017; Zhang et al., 2018). MFC-mediated electrochemical reduction of 5 mg L−1 Cu2+ reached maximum removal rate of 97.8%, while achieving a maximum power density of 1.23 ± 0.02 W m−2 by anode EABs dominated by Geobacter (Zhang et al., 2018). Unlike traditional bioenergy technologies based on incineration (heating or cooking with open flame) and gasification, the combination of EAB and other microbial guilds (e.g., Pseudomonas, Desulfobulbus) in MFCs can achieve efficient conversion of waste organic substances to electricity without deleterious effects on human health and environment from toxic byproduct (e.g., SO2, NO2, polycyclic aromatic hydrocarbons [PAHs]) (Chen et al., 2019; Logan, 2009). As a derivative technology of MFC, microbial electrolysis cells (MECs) are designed to generate hydrogen at cathode with electricity production by electron transfer from Geobacter and Shewanella to anode (Logan et al., 2008). Especially, anodic Geobacter populations were of utmost importance for both the electricity generation in MFC and hydrogen production in MEC (Kiely et al., 2011). Compared to the traditional fuel cells, the utilization of waste biomass as substrate in MFCs eliminates the need for constant external supply of fuel. Therefore, coupling of MFCs with wastewater treatment is economically attracting (Trapero et al., 2017). Even though effective application of this technology for practical applications is still limited, MFC has been proposed for large-scale wastewater treatment process in the future (Li et al., 2013; Santoro et al., 2017; Slate et al., 2019).