**1. Introduction**

Due to the increasing worldwide population, industries, etc. the commercial, and domestic demands of energy are on their rising trends. The rapidly growing population and industrialization have carried out a vast influence on environment contamination such as water, air pollution [1]. Therefore, it has been essential to overcome the energy demand without environmental pollution. In past decades, wastewater was considered as an efficient source for generation of energy. Hence, there is a crucial need to introduce a method by improving energy recovery from water resources without high expenditure. To respond to this inefficiency, the scientific community introduced a new method called microbial fuel cells (MFCs), considered as the most economical and environmentally stable process. Logan et al. [2] defined the MFCs as a most prospective approach to generate energy along with treatment of wastewater by using microbes as catalysts. Similarly, Nikhil et al. [3]

studied that the MFCs have the capability to generate electricity along with the treatment of wastewater and raised it to be an ideal solution for energy and water issues. Usually, MFCs presented extensive advantages as compared to other conventional techniques such as less activated sludge produced from wastewater, energy input is not present for aeration and the system works at various pH, temperature and substrate to generate electricity through using microorganism electro-catalyst. Despite all developments in MFCs, even an ideal improvement in power density was observed earlier but still practical application has not been implemented in the market due to the less electric efficiency. There are several factors such as electrodes (anode & cathode), incolumn source, proton exchange membrane, MFCs scale, design and organic substrate etc. which directly affect the operation of MFCs [4]. Moreover, the MFCs have two basic types of electrodes in the system such as anode and cathode system. In all factors, one of the most important aspects is the electrode material, particularly anode electrode and its working efficiency. The lower transportation rate of electrons becomes a major problem which decreases the electric performance of the MFCs. In early stage, a large variety of electrodes (activated carbon cloth, carbon felt, cloth, rod, mesh, fiber, paper, brushes, 3D graphite, glassy carbon, granular graphite, graphite block, graphite felt, reticulated vitreous carbon and graphite oxide) have been widely studied which were made using different materials [5]. Both types of electrodes play a significant role in the performance of the system but regarding in terms of functionality, anode attracted a lot of attention by researchers [6].

Furthermore, the organic substrate is oxidized by electrochemical active microbes usually known as exoelectrogens which are present on the surface of anode. The exoelectrogens produce the electrons/protons and significantly reduce the toxic effect of pollutants from wastewater. The redox reaction is thermodynamically significant, releasing electrons by microbes' stream from anode toward the cathode electrode through the provided outside circuit, and thus producing electricity. Therefore, it is not difficult to say that the MFCs performance depends on efficiency of the electrode material (anode and cathode material) [7, 8]. Furthermore, to promote the rate of organic substrate oxidation at the surface of anode electrode, a significant development is required for anode material to increase the electron transportation. The high oxidation rate led to the high generation of electrons which can travel toward the cathode so an efficient medium (anode material) can effectively transfer the electrons from anode to cathode chamber. Recently, Yaqoob et al. [7] reported the modified graphene/polyaniline nanocomposite as anode vs. graphite as cathode in MFCs to enhance electron transportation. A.A.Y. et al. reported the 87.71 mA m−2 current density which was higher as compared to simple graphite anode. In another study, Yaqoob et al. [8] also proved that the modification of anode electrodes can bring high electron transfer which led to high performance of MFCs. A.A.Y. et al. also used the graphene/ZnO composite as anode and reported 142.98 mA m−2 current density. In the previous literature, ElMekawy et al. [9] studied the graphene-based electrodes (anode & cathode) and compared the performance in terms of electricity. The highest achieved power density was reported as 4 W m−2 by using graphene-based anode electrodes vs. carbon brushes as cathode. Similarly, modified cathode (graphene-based) was offered with a power density as 3.5 W m−2. Therefore, this comparatively higher power density by graphene modified anode, was considered more efficient as compared to graphene-modified cathode. The reason for higher power density in case of graphene modified anode is due to the high electron transportation toward cathode. While in graphene-based cathode the energy was low due to poor rate of electron transportation from anode. Therefore, the generated electron required

*Electrode Material as Anode for Improving the Electrochemical Performance of Microbial Fuel… DOI: http://dx.doi.org/10.5772/intechopen.98595*

an effective anode material to transfer the electrons rapidly toward the cathode. Moreover, the authors also proposed that graphene anode modification is more important than the cathode electrode to get better performance. The anode material braked the progress of MFCs at practical application due to low conductive material, bacterial toxicity, corrosive and cost issues. The significant value, role of anode and above-mentioned issues urge the utilization of highly conductive material as anode material to overcome these problems. Generally, some properties such as high surface area, high conductivity, biocompatibility, cost effectiveness, high mechanical and thermal stability are essential required parameters for high performance of anode electrode [9]. To overcome these current challenges, the utilization of high-performance material will be considered as a great idea. Although the materials used mostly are carbon-based, less effort seems to develop graphene and its derivatives-based electrodes. Therefore, the present chapter describes the role and working mechanism of anode oxidation in MFCs. Presently, several efforts are still ongoing to improve the anode material as electrodes for high performance related to MFCs. Moreover, this chapter will be proved very useful for the researcher to develop an idea for further improvement regarding anode electrodes. However, the basic required properties and future recommendations for high performance anode are briefly summarized in this article.
