**1. Introduction**

Global energy consumption has increased gradually in recent years due to population growth, and economic development and industrialization. Also, global warming and environmental pollution worsened everyday too much of automobile vehicles and industrialization. Hence, the development of renewable energy sources became increasingly important. Hydrogen is one the most promising clean and sustainable energy sources because it emits only water as a byproduct and generates no carbon emissions [1]. Hydrogen has a quality of high energy carrier including high energy density that is more than ordinary petroleum and diesel fuel [2]. At the moment, global hydrogen production is estimated to over 500 billion cube meters per year [3]. It can be used in much industrial application including fertilizer, petroleum refining operation, fuel cell, chemical industries [4]. Hydrogen can be generated from variety of renewable and non-renewable sources like water and fossil fuels [5], oil reforming [6], coal gasification [7], biomass [8], water electrolysis [9].

Many approaches for manufacturing hydrogen are currently available however water electrolysis is one of the most capable methods for producing hydrogen as a product and oxygen as a by-product. At the moment, only 4% of hydrogen can be obtained by electrolysis of water [10]. Water electrolysis also provides a number of advantages, such as high cell efficiency and a greater hydrogen generation rate with excellent purity, making it a better method for converting water to electrical energy via low-temperature fuel cells. The water molecule is the reactant in the electrolysis process, and under the influence of electricity, it is split into hydrogen (H2) and oxygen (O2). Based on the electrolyte, operating conditions, and ionic agents (OH− , H+ , O2 − ), water electrolysis is separated into four categories: alkaline water electrolysis (ii), solid oxide electrolysis (SOE), microbial electrolysis cells (MEC), and PEM electrolysis of water [11]. The phenomenon was first described by Troostwijk and Diemann in 1789 [12], and it is a well-established technique for commercial hydrogen production up to the megawatt range in the world.

The hydroxyl ions (OH<sup>−</sup> ) flow through the porous diaphragm to the anode under the effect of the electrical circuit between anode and cathode, where they are discharged to 12 molecules of oxygen (O2) and one molecule of water (H2O). Alkaline electrolysis is performed at lower temperatures, such as 30–80°C, with an aqueous solution (KOH/NaOH) as the electrolyte and a 20–30% concentration. Alkaline water electrolysis uses an asbestos diaphragm and nickel materials as electrodes [13]. In the 1980s, Donitz and Erdle proposed solid oxide electrolysis (SOE). Solid oxide electrolysis has attracted a lot of interest since it converts electrical energy into chemical energy while also producing ultra-pure hydrogen with a higher efficiency. Solid oxide electrolysis runs at high pressures and temperatures of 500–850°C and consumes water in the form of steam. Nickel/zirconia is commonly utilized as an O2 conductor in solid oxide electrolysis [14].

Microbial electrolysis cell (MEC) technology may produce hydrogen from organic matter such as renewable biomass and wastewaters. MEC technology is similar to microbial fuel cells (MFCs), however the operational concept is reversed [15]. In 2005, two independent research institutions, Penn State University and Wageningen University in the Netherlands, established the first Microbial electrolysis cell (MEC) method. Electrical energy is turned into chemical energy in microbial electrolysis cells (MECs). Under the influence of an electric current, MECs created hydrogen from organic molecules. Microbes oxidize the substrate at the anode side of the microbial electrolysis process, producing CO2, protons, and electrons. The electrons move to the cathode side via the external circuit, while the protons travel to the cathode via a proton conducting membrane (electrolyte), where the protons and electrons combine to form hydrogen [15]. However, this MEC technology is still in the early stages of development, and various issues like as high internal resistance,

*Zero Emission Hydrogen Fuelled Fuel Cell Vehicle and Advanced Strategy on Internal… DOI: http://dx.doi.org/10.5772/intechopen.102057*

electrode materials, and intricate design must be addressed before the technology can be commercialized [16].

In the early 1950s, Grubb achieved the first PEM water electrolysis, and General Electric Co. was created in 1966 to overcome the drawbacks of alkaline water electrolysis. PEM water electrolysis technique, which is similar to PEM fuel cell technology [17], used solid poly sulfated membranes (Nafion®, fumapem®) as an electrolyte (proton conductor). Lower gas permeability, strong proton conductivity (0.1 0.02 S cm−1), thinness (20–300 m), and high-pressure functionality are all advantages of these proton exchange membranes. In terms of sustainability and environmental impact, PEM water electrolysis is one of the most environmentally benign methods for converting renewable energy to high purity hydrogen. Another prospective PEM water electrolysis device has a small footprint, high current density (over 2 A cm−2), high efficiency, fast responsiveness, and operates at lower temperatures (20–80°C) while producing ultrapure hydrogen as a byproduct [17].
