Hydrogen & Fuel Cells

We are trying to design a way to power vehicles of the future by using the hydrogen that is stored as a fuel cell for Motor Vehicles in order to obtain energy for the vehicle we need to rejoin the hydrogen with oxygen and this is done most efficiently in what is called a fuel cell in an ordinary electric cell a metal say zinc ionizes at one electrode the anode giving off two electrons the electrons are pushed around the circuit carrying energy - for example a motor and absorbed by metal ions of a less reactive metal say copper the circuit is completed by the movement of metal ions through the solution in a fuel cell the reactants are gases instead of metals hydrogen gives its electrons the electrons flow round driving the motor and arrive at the cathode where they are recombined with hydrogen in the presence of the reactive gas oxygen which provides the driving energy to form water again the electrodes can be made of porous carbon coated with a catalyst such as platinum or nickel advantage of combining a fuel and oxygen In a Cell is that you can in theory convert most of the chemical energy to electricity whereas burning them has happens in the internal combustion engine of a car has a maximum efficiency of about 50% and in practice only about 25% of the chemical energy does useful work in driving the engine the rest comes out as waste heat there are two major problems to using hydrogen fuel cells in vehicles firstly where do you get the hydrogen currently most industrial hydrogen is derived from methane and the carbon is rejected as carbon dioxide thus adding to the greenhouse effect the hope is that we can learn to mimic photosynthesis by using sunlight to split water molecules apart giving us a clean and simple source of hydrogen currently this is achieved by using photo voltaic cells to generate electricity which then electrolyte is water forming hydrogen and oxygen to take the analogy further the hydrogen is transported to the fuel cell like biomass passing along a food chain and the oxygen which we tend to take for granted is vented to the atmosphere the fuel cell then gets its oxygen from the atmosphere just like in respiration the energy is stored whilst the hydrogen and oxygen are kept apart the other problem is how to store and transport the hydrogen gas, once you've got it it's extremely difficult to liquefy and rather dangerous if kept as a gas under pressure particularly if the vehicle crashes research is therefore focusing on hydroxides compounds of elements with hydrogen which are solid or liquid at room temperature and which give out their hydrogen reversibly and without too much energy input this allows hydrogen to be pumped in reacting to form the hydroxide. Then on the journey the hydrogen is given off to be used in the fuel cell to drive the vehicle for example ammonia and borane a solid at room temperature with the same structure of ethane gives up its hydrogen on heating however it will probably be more energy efficient to run the cars on batteries which are charged from green electricity