**5. Characterization tools**

The study of MFCs can be performed by using different types of analytical, surface, biochemical, spectroscopic, and bioelectrochemical characterization methods [66]. The morphological (surface) properties analyzed characterization methods, for example, fluorescent microscopy, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) are very convenient in investigation of the microbial biofilm growth around the surface of anode. To understand the biofilm density, growth patterns, thickness, size and heterogeneity of the biofilm, electrochemical cauterizations are required. They are also suitable in reviewing the electrode porosity and membrane-based materials which were used in MFCs. The organic substrate application, product configuration and extracellular-based mediators in the MFCs and anolyte can be sensed and studied by a diversity of spectroscopic, biochemical, and electrochemical approaches [67]. The biochemical approaches e.g., redox mediator assesses are measurable and assistance in measurement the redox mediator's concentration, while spectroscopic systems such as HPLC, LC–MS and UV–VIS, are also vastly valuable in classifying and then computing the chemical classes. On the other hand, the electrochemical methods like differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), cyclic voltammetry (CV), are qualitative techniques. They help in classifying the mechanisms which are liable for electron shuttling in current peaks form on their changeable electrochemical actions. The CV has been widely used in biological-fuel cells characterization where the mediated electron transference is the main mechanism of electron transportation. The *Shewanella sp.* secretion (flavins) and the extracellular electron transference have been acknowledged via CV and their meditations were then calculated by means of chromatographic techniques. Gradually, study based on alternative electrochemical methods, specifically electrochemical impedance spectroscopy (EIS), is today being employed. In voltammetry, through imposing possible phases or curves, the electrode is determined to a disorder from symmetry and the answer will be detected which a fleeting signal is frequently. Though, in EIS, the scheme is disconcerted with an irregular current of minor magnitude and the method follows the steady state. Additionally, the important benefit of impedance analysis is that the method is non-destructive or non-intrusive [68]. It can be achieved in the working MFCs without troubling the arrangement, while other characterization apparatuses deliberated above need the MFCs to be concerned and the products are being calm for succeeding analyses. Later, EIS is investigated in a stable state of bioelectrochemical method wherever the analyses are done without changing the current–voltage characters of the fuel cell system [69]. EIS has also been extensively studied in different zones of bioelectrochemical investigation such as fuel cells and corrosion. Moreover, EIS is a valuable tool to examine the influence of diverse internal resistances to the total impedance of the MFCs.

### **6. Current challenges and future perspectives**

The MFCs received a lot of attention in the modern era and offered significant results. There are some modern challenges which still need attention for high electrochemical performance. The utilization of conventional electrodes has failed to improve the electric efficiency in terms of MFCs. There are various challenges related with anodes which create a hurdle in the case of MFCs applications at a commercial scale:

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

