Renewable fuels and environmental remediation are of paramount importance in today's world due to escalating concerns about climate change, pollution, and the finite nature of fossil fuels. Transitioning to sustainable energy sources and addressing environmental pollution has become an urgent necessity. Photocatalysis, particularly harnessing solar energy to drive chemical reactions for environmental remediation and clean fuel production, holds significant promise among emerging technologies. As a benchmark semiconductor in photocatalysis, TiO2 photocatalyst offers an excellent solution for environmental remediation and serves as a key tool in energy conversion and chemical synthesis. Despite its status as the default photocatalyst, TiO2 suffers from drawbacks such as a high recombination rate of charge carriers, low electrical conductivity, and limited absorption in the visible light spectrum. This review provides an in-depth exploration of the fundamental principles of photocatalytic reactions and presents recent advancements in the development of TiO2 photocatalysts. It specifically focuses on strategic approaches aimed at enhancing the performance of TiO2 photocatalysts, including improving visible light absorption for efficient solar energy harvesting, enhancing charge separation and transportation efficiency, and ensuring stability for robust photocatalysis. Additionally, the review delves into the application of photodegradation and photocatalysis, particularly in critical processes such as water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide generation, and alcohol oxidation. It also highlights the novel use of TiO2 in plastic polymerization and degradation, showcasing its potential for converting plastic waste into valuable chemicals and fuels, thereby offering sustainable waste management solutions. By addressing these essential areas, the review offers valuable insights into the potential of TiO2 photocatalysis for addressing pressing environmental and energy challenges. Furthermore, the review encompasses the application of TiO2 photochromic systems, expanding its scope to include other innovative research and applications. Finally, it addresses the underlying challenges and provides perspectives on the future development of TiO2 photocatalysts. Through addressing these issues and implementing innovative strategies, TiO2 photocatalysis can continue to evolve and play a pivotal role in sustainable energy and environmental applications.