Solar Water Splitting

  Solar-water splitting – A sustainable route for renewable hydrogen

Water splitting is a process of dissociation of water molecules into hydrogen and oxygen. Extraction of hydrogen from water molecules is an important and green approach, since water exists in abundance on our planet and also the envisaged process would not produce any harmful by-products. However, the process of water-splitting still requires energy as it involves positive change to the Gibbs free energy (∆G° = 113 kcal/mol). 

Water can be split by several methods like; (i) electrolysis, in which electric current passed through water splits water into its components – hydrogen and oxygen; (ii) biological methods in which algae is used to split water; and (iii) thermochemical methods that require high temperature. Among all the above, solar-water splitting is a sustainable route for renewable hydrogen production. Hydrogen produced is a carbon-free fuel; hence, efficient storage of solar energy into hydrogen and the use of later as fuel can alleviate many energy and environmental issues.

The idea of solar-water splitting for hydrogen production is derived primarily from the naturally occurring photosynthesis process in which plants use solar energy to make their food in the form of complex molecules like carbohydrates. On a similar line, solar energy can be used in the splitting of water to produce hydrogen as fuel. To accelerate the development of hydrogen produced by renewable solar energy, several techniques have been developed like photoelectrochemical water splitting (PEC), photocatalytic, photovoltaic-electrolysis etc. In these techniques, PEC water splitting is simplest, efficient, cheap and clean method for production of hydrogen.