Photocatalytic Hydrogen Generation

Environmental transformations with catastrophic effects have been observed in the world. Among these, it can mention climate change due to greenhouse gases, mainly due to CO2. In this sense, heads of state around the world have committed themselves to new forms of energy that do not harm the planet. Among these, hydrogen has stood out, as it has an energy potential (142 kJ/g) much higher than fossil fuels. In addition, its burning produces only water vapor. There are several hydrogen production technologies, with the process being classified by colors depending on the amount of CO2 released into the environment. Among these, the process of water electrolysis and water photolysis using semiconductors has drawn attention for being a green technology. However, the popularization of hydrogen as a fuel presents several challenges to be overcome. This is because traditional storage methods, such as hydrogen compression or liquefaction, are economically inefficient techniques, in addition to presenting safety risks, as H2 gas is highly flammable. In this sense, the hydrolysis of hydrogen-rich inorganic hydrides, such as NH3BH3, NaBH4, and B2(OH)4, is considered a promising alternative. The evolution of hydrogen through this pathway consists of a process that takes place in water at room temperature and atmospheric pressure. However, it is a slow reaction that requires the use of catalysts. Among these, metals such as platinum, nickel, and cobalt at the nanometric scale stand out. Such nanocatalysts have a natural tendency to agglomerate and, therefore, can be anchored in support materials such as graphene-based materials. In recent years, investments have been made in improving the photocatalytic performance of semiconductors, used in photocatalysis. Among the improvements, the formation of a graphene-based semiconductor composite stands out. The delocalized conjugate π system present in these carbon-based materials can function as electron reservoirs to accept and transport photogenerated electrons for rapid charge transfer and separation. In this sense, this chapter will discuss Fundamentals and Applications Graphene-Based Photocatalysts for different applications of evolution of hydrogen.