Hydrogen production is a potential capability of renewable clean energy. Industrial hydrogen production is derived from the process of reforming natural gas, which requires a significant amount of nonrenewable energy and also results in the generation of the greenhouse gas carbon dioxide. Water splitting electrolysis is a highly promising method for efficiently producing hydrogen through energy conversion and storage, with catalysis or electrocatalysis playing a crucial part. Photo-electrochemical water splitting is a highly promising method for producing H2, as it is both sustainable and free from pollutants. Hence, the pursuit of proficient and cost-effective technologies for photo-electrochemical water splitting has been a significant objective for researchers globally. Employing green energy technologies to minimize total energy usage is of greater significance for H2 production. Utilizing various green energy technologies to harvest and convert energy from the environment for water splitting can effectively reduce the need for external electricity. This chapter provides a fundamental, novel materials used and novel approaches and emerging technologies in water splitting.