Abstract:
The need to develop the technologies which are friendly to the environment is quite essential to tackle the problems being caused by pollution and to meet the increase in demand of energy. The nanocomposites based upon the phenomenon of photocatalysis seem to be the ideal solution. But the majority of the photocatalytic active substances show absorbance only in the ultra-violet region but this region only constitutes 3% of the total spectrum of light. The photocatalysts absorbing in the visible region are not considered efficient because of the low length of diffusion of carriers which leads to the insufficient harvesting of solar light and energy. Many transition elements have, thus, been utilized by the researchers to obtain the substances which are advantageous to deal with the environmental issues.
In the recent years, semiconductors of transition metal oxides, such as titanium oxide (TiO2), zinc oxide (ZnO), bismuth oxide (Bi2O3) and iron oxide (Fe2O3) have emerged as excellent candidates for photocatalysis due to their non-toxicity, band gap, inertness and chemical stability. But among these transition metal oxides, manganese dioxide has proved to be a promising one being of low cost, naturally abundant and eco-friendly. But the rate of recombination of pairs of electrons-hole is extremely low making the degradation process quite slow. Graphitic carbon nitride (g-C3N4) has appeared as an efficient photocatalyst because of its mechanical and chemical stability and low cost. A lone pair of electrons resides on the N-atom which induces enhanced polarity in the molecule of g-C3N4. This also results in the enhancement in wettability and mobility for carrying charges. The photocatalytic activity of g-C3N4 gets limited because of the slow rate of recombination of the electron-hole pairs. The formation of heterojunction between transition metal oxides and graphitic carbon nitride compensate the shortcomings of both the materials.
