Sustainable hydrogen generation substrates, catalysts and methods: An overview

Because of the increasing demand for energy, various alternative sources of energy generation are being examined. Interest in hydrogen generation is on the rise due to its potential as a scalable green energy source, its transportability, and other positive factors. While various studies have been conducted on hydrogen generation, this review explores three major factors in hydrogen generation in relation to sustainability: substrates or hydrogen storage media, catalysts for speeding up the rate of hydrogen reaction, and methods employed. The media used to store the hydrogen, such as metal hydrides and complex hydrides, is examined in relationship to hydrogen yield, ease of hydrogen generation or treatment, cost and environmental friendliness. A list of popular catalysts - particularly precious/rare earth metals, strong acids and weak acids - is examined and compared in terms of hydrogen yield, environmental friendliness, and cost. The recent trend in hydrogen generation techniques and material treatment innovations such as hydrolysis, and ball milling of nanocomposites is examined. Innovations in hydrogen storage material selection and techniques will go a long way in lowering hydrogen generation cost, increasing hydrogen yield and ameliorating negative environmental impacts.