Algal Hydrogen Production using Electrochemical and Fermentative Electron Provision /

Abstract

The increasing concern regarding the depleting conventional energy resources has sparked an interest in the development of renewable energy resources. Among these resources, solar technologies have gained the most interest since it is the greatest energy source for the planet. Along with energy acquisition, energy storage is also an important issue and requires a reliable solution if solar technologies are to become the prime source of energy for humanity. One of the solutions gaining momentum nowadays is to switch to Hydrogen and use it as the primary energy carrier. Traditional methods of hydrogen production are not sustainable and efforts are being made to improve the reliability and performance of innovative and inspired technologies. One of these technologies is algal hydrogen production which relies on the natural mechanisms many microorganism have evolved in order to survive harsh conditions. Hydrogenase systems present in some algae allow them to carry out life sustaining reactions and produce hydrogen as a by-product. This process is linked strongly with the electron transport chain and relies on a constant supply of electrons and protons to continue. Here the focus has been on the provision of electrons in order to facilitate this process. Fermentative reactions can be a source of electrons which are released as a result of dissociation of any number of substrates. One of the well-known species, Saccharomyces Cerevisiae has been used to dissociate a simple sugar, glucose, and hence become a source of electrons for the algae to continue the hydrogen evolution process. The provision of electrons has been tackled in two different ways one where the yeast and the algae are in indirect contact i.e. in an MFC and the other where they are directly mixed together. Experimentation showed that direct mixing yielded higher amounts of hydrogen (276 μl/g.hr) owing to the interaction of algae and yeast in the mixture. The indirect contact in the MFC was enhanced to create an MEC, where external potential was provided, but the results were unfavourable. This led to the conclusion that direct mixing is a better and easier way of achieving improved hydrogen production. Along with this, Hematite based photoanodes were also developed in Arizona State University. The photoanodes were tested for their ability to split water under simulated sunlight and contained additives like Copper and Zinc oxides along with MWCNTs and Graphene nano platelets to improve electrical properties. The highest photocurrent achieved with the developed anodes was approximately 10 mA/cm2. By comparing these biological and inorganic systems, it can be clearly seen that the Hematite based Hydrogen production system is much more efficient and produces higher amounts of Hydrogen.