2
Figure 1.1: Concerted effort of experimentalists and theoreticians. The mutual
feedback from each other leads to an efficient materials design and understanding
of a given physical/chemical process. Image courtesy: SUNCAT
(http://suncat.stanford.edu).
Among many possible ways to utilize solar energy one of the most promising
ways is to harvest the solar energy for the photon assisted water splitting.
The process proceeds via absorption of sunlight with a semiconducting material
and the generated electron-hole pairs can be used to produce hydrogen by
splitting the water 3. Unfortunately, the process is not as simple as it sounds
and the main challenge lies in finding a material which can accomplish the
whole process of hydrogen evolution efficiently. In order to do so, a material
should be able to absorb the sunlight to generate electron-hole pairs and evolve
hydrogen at cathode and oxygen at anode using the generated electron and
hole respectively. All these criteria are hard to meet by a single material. An
additional constraint is also imposed by the abundance and toxicity of different
elements going in the workflow of materials design 4. Because of all the
complications involved, even after decades of explorations for a suitable material
for photoelectrochemical watersplitting, the best material has not been