Insights on pathways for hydrogen generation from ethanol

Growing apprehensions on greenhouse gas emissions, global warming, and pollution problems are directly related to fossil fuels consumption. To counteract these environmental issues, global efforts are being made to diversify energy supplies towards cleaner fuels, especially for the transportation sector. Hydrogen surpasses all other biofuels such as biodiesel, bio-oil, ethanol, and butanol because of its high energy content, no greenhouse gas emissions, rapid combustion properties, non-corrosive nature, and physical state. Hydrogen production from methane and methanol, through reforming reactions, has been thoroughly studied and these are well-entrenched industrial technologies. However, ethanol is an attractive feedstock for hydrogen production because it is less toxic than methanol and can easily be produced from renewable biomass. Interest in the conversion of ethanol to hydrogen through several thermochemical, hydrothermal, photochemical, and electrochemical technologies has grown recently. In this review, different thermochemical, hydrothermal, photochemical, and electrochemical technologies for ethanol to hydrogen conversion are comprehensively discussed. Ethanol conversion technologies reviewed in this paper include steam reforming, partial oxidation, autothermal reforming, alkaline-enhanced reforming, dehydrogenation, supercritical water gasification, photocatalysis, and electrocatalysis. Current advancements, technical challenges, and future perspectives of each technology are thoroughly discussed. This technical compilation brings together various techniques that are being explored for hydrogen production from ethanol.