Hydrogen Production from Renewables

Abstract

AbstractHydrogen is considered to be critical for energy and environmental sustainability. However, as hydrogen is currently produced from fossil fuels, it emits large amounts of carbon dioxide along the reforming steps. The technical challenges to achieve a stable hydrogen economy include improving process efficiencies, lowering the cost of production, and harnessing renewable sources for hydrogen production. Lignocellulosic biomass is one of the most abundant forms of renewable resources. When this precursor is used, virtually no net greenhouse gas emissions result because a natural cycle is maintained, in which carbon is extracted from the atmosphere during plant growth and is released during hydrogen production. This article focuses on recent developments in biomass and biomass‐derived product conversion to H2. The second option explored here is the conversion of solar energy into hydrogen via water‐splitting processes assisted by two‐step metal‐oxide thermochemical cycles or by photosemiconductor catalysts. The conversion of solar energy into a clean fuel (H2) is the most promising technology for the future because large quantities of hydrogen can potentially be generated in a clean and sustainable manner. Undoubtedly, the conversion of solar energy into H2is one of the greatest challenges scientists are facing in the twenty first century. A survey is presented of the advances made in the development of metal oxide redox pairs since the pioneering work by Nakamura in 1977 and in the development of photocatalysts for water splitting under visible light since the first work of Fujishima and Honda in 1972. The very high thermal reduction temperature used for the metal oxide redox pairs developed until now leads to severe sintering, melting, and vaporization of materials, decreasing the efficiency and durability in the cyclic operation. Consequently, the application of material science and engineering to the development of materials with lower reduction temperature and high water‐splitting ability is still a challenge in this scientific area and an overview of the progress is provided in this article. On the other hand, there are still major challenges in the development of photocatalysts with improved efficiencies for hydrogen production from water using solar energy. An overview is provided in this article of research strategies and approaches adopted in the search for photocatalysts for water splitting under visible light (new photocatalyst materials and the control of the synthesis of materials for customizing the crystallinity, electronic structure, and morphology of catalysts at nanometric scale).