摘要： Energy and clean environmental conditions are the two basic requirements for the survival and progress of human civilization. The Industrial Revolution was a prime factor in the rapid development of human society. However, the industrial malpractices of waste disposal and extensive use of fossil fuels have led human society to face a number of challenges such as global warming, and water and air pollution. Also, the extensive use of pesticides in agriculture has led to high toxicity in soil and ground water, which can pose a big threat to human and wildlife [1]. A recent WHO report shows that about 3.7 million people globally die each year in the 21st century from the hazards of water and air pollution, and 92% of the world’s population still does not have access to pure water [2]. The fossil fuel resources are limited in their ability to cater to the energy demands of the growing world’s population and are on the verge of exhaustion in the near future. This has led to the fear of energy crises, which can prove fatal for human society. Hence, the search for an ultimate and clean energy source, as well as the development of technologies for the remediation of hazardous materials from the environment have become topics of high international concern. There have been several attempts to harness alternative energy sources such as wind, water tides, biomass and solar energy, etc., as well as to design methods for the remediation of environmental pollutants. Hence, the development of cleaner, low carbon, and sustainable technologies is a bigger challenge for scientists and engineers worldwide [3]. Some technologies have been developed to harness alternative energy sources, but these have proven either inefficient or too expensive. Also, efforts toward the removal of harmful environmental pollutants are either inefficient or have their own side effects [4]. Among renewable energy sources, solar energy is available in abundance and has the potential for overcoming current environmental impacts. However, its unavailability at night, and during rainy and foggy seasons make it difficult to properly harness. Hence, transforming energy from sunlight to the chemical energy of hydrogen through photocatalytic water splitting could be a more promising approach [5]. Solar energy is also gaining attention for water treatment. There have been a number of metal oxide-based photocatalysts prepared for degrading organic pollutants such as dyes and pesticides. This chapter stresses H2 generation through photocatalytic and photoelectrochemical water splitting and photocatalytic water treatment using two well-known photocatalysts, ZnO and TiO2.