The global energy crisis and environmental degradation have become two of the major issues of the twentyfirst century as a result of rapid industrialization, population expansion, and agricultural progress. The pollution and emission from various factories, cars, and chemical plants have increased the NOx and CO2 levels in the atmosphere. Scientists and governments are, therefore, focused on finding primary energy sources that are alternatives to fossil fuels and nuclear power. In this direction, nanoscale photocatalytic materials have recently received a lot of multidisciplinary research to address global energy production challenges. Nanotechnology provides a new platform that is low-cost, reasonable, low risk of secondary contamination, cost-efficient, and successful in simultaneously removing many contaminants from contaminated wastewater. Photo catalysis works on the idea that nanomaterials absorb photons to produce holes and electrons, which drive the oxidation-reduction cycle. Nanoscale photo catalysts (nano catalysts) with efficient properties (great efficiency, high surface area, and small bandgap) are becoming popular in green and sustainable fuel generation applications. In this chapter, we comprehensively discussed various nano catalysts that convert solar energy into clean and renewable fuel by photocatalytic water splitting to generate hydrogen or reduce NOx or CO2 emissions is an appealing scientific and technological objective for meeting rising global energy demand and reducing the impact of energy production on climate change. We have also elaborated the underlying photocatalytic processes and their associated mechanisms, as well as the development of novel catalysts with increased efficiency and functionality for the production of clean and renewable fuels for commercial applications. Various studies have been summarized to amend the reducing ability of the photo catalyst in order to improve the amount and execution of active sites on the surface of the catalyst. We have also discussed the methods to increase the efficiency of fuel production by cost-effective and inexhaustible resources. We have also addressed the viewpoints and prognosis on future advances in this sector, as well as a comprehensive summary of the work done to solve the difficulties and current successes on fuel production and energy conversion.