Fuel cells convert the chemical energy of in fuel mainly hydrogen efficiently to electricity without combustion. The process has significantly low emissions with water as the main product of the reaction   compared to conventional equipment/techniques that are associate with greenhouse gas emissions. The three main parts of a fuel cell assemble are the anode, cathode, and electrolyte. A catalyst oxidizes fuel with ions travelling via the electrolyte. At the cathode ions are reunited with the electrons. It is the electrons produced at the cathode that generate electrons which make the electrical circuit. Fuel cells development  partially focuses on optimization of catalytic  the layer 0f the  catalytic electrodes, and by reducing  metal without appreciable loss of the fuel cell performance. For fuel cells, power supply is uninterrupted during fuel supply and the oxidant, unlike a battery which relies on stored energy and is affected by amount of reagent available. The  theoretical  efficiency fuel cells is about 90%  while in thermal engines the efficiency is about  40% for optimum conditions. However, practical fuel cell efficiency is usually less than 60%. which is still significantly greater than efficiency of combustion engines.  The fuel cells operate with continuous replenishment of the fuel, and the oxidant at active electrode area and with no need for recharging. The elements of a fuel cell are the electrode, an oxidant or an air electrode, and an electrolyte. Common fuel cells used are hydrogen, oxygen (H₂, O₂), hydrazine (N₂H₄, O₂), carbon/coal (C, O₂) methane (CH₄, O₂). Hydrogen-powered fuel cells emit only water with virtually no pollutant emissions. On the other hand, fuel cells powered by hydrocarbon-based fuels have the potential to Employing hydrocarbon-based fuel inevitably leads to CO₂ emission.  Since fuel cells are not subject to the limitations of the Carnot cycle efficiency, fuel cells attain higher efficiency that can be more than twice the efficiency of internal combustion engines. The transport sector operates with fuel cells having efficiency of up to 65%, compared to 25% for internal combustion engines.  Application of heat produced by in fuel cells reaction for in combined heat and power (CHP) systems, increases overall efficiency to over 85%. Although fuel cells have significantly higher conversion efficiency compared to the internal combustion engines or and gas turbines across their output power range making them ideal for a variety of applications ranging from mobile phones to large-scale power generation, their largescale adoption is limited by high cost and lower reliability. The key to sustainability   of fuel cells revolves around the production of hydrogen, the efficiency and capacity factor of fuel cells relative to other renewable sources of energy as well as the size of the installation