Production of Hydrogen by Photo-electrochemical methods

Steam reforming of methane which results in CO2 emission is a major method of hydrogen production till date. Morever, any form of dependence on the fossil fuels cannot be considered as environmentally friendly and is not an assured source in the long run. In this scenario, electrolysis of water is an ideal method of distributed hydrogen production if one can derive the electrical energy from renewable and non- polluting sources. Photoelectrochemical (PEC) water electrolysis is a single step hydrogen production method, where in light energy is directly converted to chemical energy thus eliminating the inherent losses of the naive water electrolysis.

In a typical PEC cell, the semiconducting photoanode, on shining with light, develops holes and electrons thus causing reduction of water to genarate oxygen at anode and oxidation of H+ ions to generate hydrogen at cathode. An ideal photoanode material must be stable in the corrosive alkaline or acidic electrolyte medium, should have energy band gap such that “solar energy” is utilized to its fullest. Such materials have to be engineered upon due to the fact that the presently available materials are not suiting these requirements. At IIT Madras, a PEC hydrogen production setup has been developed and preliminary studies on TiO2 thin films, grown using reactive RF magnetron sputter technique at different substrate temperature, as photoanode material have been carried out. We are in the process of developing novel photoanode materials which can utilize the maximum solar energy.

Hydrogen in metals, composites and carbon nanotubes

Hydrogen storage properties of various types of alloys, carbon nanotubes and graphene have been studied . We have already  developed Zr and Mm (Mm = Mischmetal) based materials having storage capacities comparable to the materials used for commercial hydrogen storage. The current focus is on the study of hydrogen adsorption and kinetics of Mg based composite materials.

Even though Magnesium and Mg based alloys have high hydrogen storage capacity, they require to undergo a hard activation process, have slow reaction kinetics and high working temperature. Tailoring nanomaterials to overcome these difficulties is a stepping stone towards the realisation of a hydrogen economy.

Design and development of metal hydride storage devices

A metal hydride based hydrogen storage device has been designed and fabricated. The device is made of stainless steel (SS) and can withstand high operating pressures. A porous sintered SS filter acts as a barrier for the alloy powder through which hydrogen is distributed or collected from the alloy. Inbuilt heat exchangers are provided to facilitate hydrogen charging and discharging.

Diffusion of hydrogen in alloys

Apart from the three major steps involved in hydrogen technology, the fundamental studies of hydrogen interstitial diffusion in materials is also carried out. The bulk diffusion coefficients of hydrogen have been measured from the kinetics of hydrogen absorption reaction. An experimental facility working on the principle of pressure reduction has been specially designed and developed using stainless steel tubes (NOVA), high pressure needle valves (NOVA) and pressure transducers for the measurement of diffusion coefficients in materials.
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