As time goes on, technological advances need more well-organized sources of power. At the vanguard of research for these power sources are hydrogen fuel cells. This power source takes in the most plentiful element in the universe, Hydrogen, and yields huge power without burning or pollution. The three aspects of this scientific step forward are the fuel cells, hydrogen production, and hydrogen storage.
Fuel cells are the devices which convert hydrogen into electricity. The technology uses here much similar to which use in battery, but with a little difference and depend on the type of electrolyte. . According to the National Renewable Energy Laboratory, or NREL, like the battery, fuel cells use chemical reactions to generate electricity rather than combustion. Unlike the battery, however, the ingredients for this reaction are not stored within the cell, rather they are taken in from outside, making their potential so much more efficient and giving them a longer time span to power whatever happens to be connected to them[1]. According to the United States Department of Energy, within the fuel cell, two reactions occur. One is an oxidation half-reaction at an anode and the other is a reduction half-reaction at a cathode. Under normal conditions, this process would be very slow. The manufacturers speed this up by adding a catalyst to one side of the anode and cathode each. The most common of these catalysts consists of platinum powder very thinly coated onto a carbon paper or cloth. The reactions that occur give off very large amounts of energy and do so without releasing pollutants. The only byproduct is water vapor. Hydrogen is the most abundant elements in nature and the universe, but it is in different compounds and more of these compounds are the water that covers three-quarters of the globe. Since the fuel cells require pure hydrogen, it must be separated from these compounds in a manner in which it creates renewable energy Depending on the available information there are four ways promising to complete the work and get the pure hydrogen, which is shown in the below:
Thermochemical hydrogen is produced by heating biomass with limited or no oxygen, either gasifying it to what is called syngas, a mixture of hydrogen and carbon monoxide, or liquefying it into pyrolysis oil. Syngas then goes through what is referred to as a water-gas-shift reaction to increase the amount of hydrogen. pyrolysis oil uses a steam reformation technique in conjunction with the water-gas shift reaction[2]. Electrolytic Hydrogen is formed by a process completely opposite of that of the fuel cell, taking water and breaking it apart into hydrogen and oxygen with what is called an electrolyzer. An electrolyzer takes water molecules and applies electrical current to water, separating the hydrogen atoms from oxygen atoms. This requires an inexpensive source of electricity, the leading proposal being wind energy. Wind energy benefits the most because for use with an electronic grid, the electricity of wind energy must convert from direct current to alternating current and the electrolyzer requires direct current.
To form Photoelectrochemical (PEC) hydrogen, one must "replace one electrode of an electrolyzer with photovoltaic (PV) semiconductor material to generate the electricity needed for the water-splitting reaction. Photovoltaic semiconductor material is something that converts sunlight to electricity [3]. NREL continues to say "the efficiency loss of separate steps is done away with, as is the cost of the other components of a solar cell. PEC is elegantly simple, but finding PV materials both strong enough to drive the water split and stable in a liquid system presents great challenges for researchers"[1].
The last technique scientists are researching is forming of hydrogen by means of nature. Some algae and bacteria use photosynthesis to make hydrogen instead of the usual sugar and oxygen. Challenges with this include the fact that the enzyme in the algae that produces hydrogen is hindered by oxygen, which of course, the organism also normally produces. Another research scientists are conducting is to develop microorganisms that will, by fermentation, form hydrogen instead of alcohol [4]. NREL states that hydrogen's most useful qualities as an energy source are its transportability and storage ability. However, hydrogen has a large density so scientists are researching ways to compress the gas. Scientists are able to compress the gas in pressurized tanks, but this still provides only limited driving range for vehicles and is much more obtrusive than desirable for other uses as well. Liquid hydrogen would double the density, but the energy required to do so require expensive equipment and still yields a small range of driving. Another option is to store hydrogen in higher densities in the crystalline structure of metal hydrides. Heat could then release the hydrogen for use. Science, however, cannot make high enough densities as well as the cost for doing so is not very efficient than the cost for the densities scientists can produce now. NREL then says "another possibility is chemically storing hydrogen in compounds that readily release their hydrogen. The reverse reactions, however, could not likely be performed on board or at the filling station, so the reaction byproduct would have to be retrieved from the vehicle and returned to the production plant for regeneration" [1]. Just 20 years ago, carbon-nanotube storage was discovered. NREL mainly researches this because it holds the most promise for success. Carbon-nanotube hydrogen storage takes atomically-small spheres, cylinders and other geometric shapes of simple carbon atoms. These structures "have affinities for absorbing hydrogen on their surfaces" (Hydro. Stor.). Scientists are trying to increase storage by manipulating these structures, but the process is still in the preliminary stages [5].
In conclusion, Hydrogen fuel cells are predicted to be a very promising source for energy. With the knowledge that scientists have today, this valuable opportunity will in probability be the next fuel for cars as well as homes, buildings, and whatever else requires power.

References.
1. Biswal, N., D. P. Das, et al. (2011). "Efficient hydrogen production by composite photocatalyst CdS–ZnS/Zirconium–titanium phosphate (ZTP) under visible light illumination." International Journal of Hydrogen Energy 36(21): 13452-13460.

2. Halford, C. K. and R. F. Boehm (2011). "An on sun parametric study of solar hydrogen production using WO3 photoanodes." Experimental Thermal and Fluid Science 35(1): 180-189.

3. Huang, B.-S. and M.-Y. Wey (2011). "Properties and H2 production ability of Pt photodeposited on the anatase phase transition of nitrogen-doped titanium dioxide." International Journal of Hydrogen Energy 36(16): 9479-9486.

4. Kandiel, T. A., R. Dillert, et al. (2011). "Photonic efficiency and mechanism of photocatalytic molecular hydrogen production over platinized titanium dioxide from aqueous methanol solutions." Catalysis Today 161(1): 196-201.

5. Leary, R. and A. Westwood (2011). "Carbonaceous nanomaterials for the enhancement of TiO2 photocatalysis." Carbon 49(3): 741-772.