Alkaline Fuel Cells

A fuel cell creates a voltage from the reaction of a fuel with oxygen. The electrolytes remain in the cell but the reactants flow into the cell and products flow out of the cell. The electrodes are porous graphite embedded with a platinum catalyst and the electrolyte is an aqueous solution of potassium hydroxide. The fuel cell can operate continuously as long as fuel and oxygen flow into the cell. Hydrogen gas is oxidised at the anode. The more negative redox equilibrium provides the electrons at the negative terminal.2H₂(g) + 4OH^-(aq) ⇌ 4H₂O(l) + 4e^-Electrons travel to the cathode. The energy of the electrons is transferred from electrical energy to power the machinery. At the cathode oxygen gas is reduced.O₂(g) + 2H₂O(l) + 4e^- ⇌ 4OH^-(aq)Water is the only product and is constantly removed from the cell. The overall equation is:H₂(g) + ½O₂(g) → H₂O(l)    E^θ_cell = +1.23 VThe efficiency of alkaline fuel cells is reduced by carbon dioxide in the air and corrosive potassium hydroxide solution may leak out. Fuel cells produce less CO₂ and air pollutants and vehicles are 40-60% efficient compared to vehicles that run on fossil fuels which are about 20% efficient. Hydrogen can be stored as a liquid under pressure, adsorbed onto the surface of a solid or absorbed within a solid material.