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Photo-catalysis has shown a prominent and effective role for the degradation of textile dyes and organic compounds on large scale to keep environment and water reservoirs clean and usable. Photo-catalysts produce hydrogen through water splitting which is an eco-friendly source of renewable energy. Photo-catalysts are used for solar cells construction. Photo-catalysis generates an electron–hole (e−–h +) pair due to light interaction. The electron–hole (e−–h +) pair produces ⋅OH and O 2 • − , which play the main role in degradation process; it leads to redox reaction and oxidizes organic pollutants to H2O and CO2. Major causes of water, air and soil pollution are organic pollutants, heavy metals and non-biodegradable dyes released by different industries. These pollutants especially phenols and dyes have seriously affected the water reservoirs. This paper gives a critical review on visible and solar light photo-catalysis and techniques used for the photo-degradation of hazardous pollutants. A systematic study has been carried out from the published literature on photo-degradation of organic pollutants, factors effecting the photo-degradation and the various operating parameters. The role of semiconductors/nano-catalysts for eco-friendly renewable energy sources, such as hydrogen and solar cells production is also elaborated for future energy crises. The published data has shown that different parameters, such as pH of the system, light intensity, catalyst amount, initial concentration and amount of photo-catalysts play a crucial role for the degradation of various dyes and organic pollutants. Photo-catalysis has also shown significant results for remediation of volatile organic pollutants and acid gases from air. This review has focused to find an efficient, low cost and result oriented photo-catalyst and the effective environment for reaction. The concluded data has shown that photo-catalysis is economically suitable and fit for the treatment of waste water, industrial effluents and energy production. [ABSTRACT FROM AUTHOR]