Hydrogen generation by biorenewable fuels depolarized water electrolysis

Abstract:
The generation of hydrogen is a basic challenge to establish a hydrogen economy with all of its benefits of low emissions and its potential of being free of fossil fuels. Commercially produced hydrogen comes mostly from fossil sources like natural gas by using a steam reforming process. This process has three major disadvantages; it consumes limited natural fossil fuels, has high energy needs, and emits CO or CO2 respectively. The aim of this work is to ascertain a process, using an ecologically sustainable basis for the synthesis of hydrogen. This work will investigate an electrochemical approach by using a water based electrolytically process. The well known electrolytically splitting of water is very energy intense. The basic idea is to reduce the energy needs by depolarizing the anodic half of an electrolyzer. Two promising types of feeds are considered, which can be gained from biomass and are available in industrial amounts and reasonable priced. Methanol can be produced by biomass gasification and glycerol is a by-product of biodiesel production. Both substances have a theoretical high depolarizing potential. Since methanol and glycerol are appended to the hemical group of alcohols, splitting and oxidizing these hydrocarbons by electrolysis will emit only CO or CO2, if completely oxidized. In fact, the CO2 would be already separated during the splitting progress and therefore storage ready. But even without storing the CO2 this way of generating hydrogen would be a CO2 neutral process, as these hydrocarbons are obtained from biomass. Glycerol and methanol are promising as a sustainable and energy efficiency alternative to the conventional process of steam reforming natural gas or water electrolysis. Although the energy needs could be significantly lowered, the promising energy reduction of the anodic reaction by splitting an alcohol water solution could not tap its full depolarizing potential. The energetic efficiency rates of methanol were about 8% and of glycerol between 6% and 7% depending on the working conditions.

Keywords:
hydrogen, biofuels