Perspectives of Nanostructured Metal Oxides and Their Heterostructures in Photoelectrochemical Water Splitting for Solar Hydrogen Production

The energy transition from fossil fuels to renewable energies demands alternative routes for producing chemical energy carrier hydrogen, which will play a central role in future energy cycles as fuel as well as energy storage and transport medium. While electrolysis of water is a proven technology to be used as grid stabilization in times of surplus supply of renewable electrical energy, other technologies are needed to supplement or even provide a basic supply of hydrogen. Photoelectrochemical water splitting and employing photoanodes, cathodes, or both in one cell design offer a direct and sustainable way of producing solar-hydrogen form water and sunlight. Among foremost materials, challenges for this application include quest for highly efficient photocatalysts, which exhibit a long-term stability under operation at ambient conditions and use abundant resources and impose little to no toxic effects on the environment. Metal oxide ceramics are therefore a promising class of materials, as either n-type photoanodes or p-type photocathodes to be used in artificial photosynthesis applications for hydrogen production. The present chapter gives a comprehensive overview on the fundamentals and the application of photoelectrochemical water splitting using binary and ternary metal oxide photoanodes and cathodes as well as composite materials thereof, including a detailed summary of various materials and materials modification, their synthesis routes and structure–property relation with respect to the state-of-the-art water-splitting efficiencies for a comparative and forward-looking analysis on solar hydrogen technology.