Materials for Renewable Energy  
Hydrogen and Hydrides
Structure and Dynamics
Stability and Kinetics
Electrochemistry
Theoretical Modelling
Instruments
Spectroscopy

Hydrogen & Hydrides

A future hydrogen economy requires dense, safe, efficient and reversible hydrogen storage materials [1]. Hydrogen as an energy carrier is difficult to store because of the low critical
temperature of 33 K, i.e. hydrogen is a gas at room temperature. Hydrogen storage in solids offers a safe alternative to storage in compressed or liquid form. The ideal hydrogen storage material should have the following properties: high gravimetric and volumetric hydrogen density, fast kinetics of (de)hydrogenation near ambient temperature, long term stability and good thermal conductivity for removing the reaction heat.

Transition metal hydrides are the state of the art hydrogen storage materials. Several hydrogen storage systems have been developed and optimized. The largest one is a ten module system with a total capacity of 5 kg of hydrogen and was successfully applied to a snow cat equipped with an internal combustion engine and demonstrated in spring 2004. A smaller unit with a total capacity of 500g was constructed for a light weight fuel cell vehicle (SAM) together with the University of Applied Science in Biel (CH). The storage units are manufactured of austenitic chromium-nickel stainless steel containing molybdenum to increase general corrosion resistance, resistance to pitting and strength at elevated temperatures (AISI 316L)  and the storage alloy used is  Ti0.93Zr0.05(Mn0.73V0.22Fe0.04)2 with a maximum hydrogen capacity of 1.88 mass%.

However, transition metal hydrides are not expected to satisfy the demand for a gravimetric hydrogen density of more than 6 mass%. The p-element complex hydrides M[AlH4]n and M[BH4]n exhibit a gravimetric hydrogen density of up to 20 mass%, but are not ready for application due to their insufficient thermodynamics (stability and kinetics). The success of an evolutionary development of hydrogen storage materials based on complex hydrides using models and concepts of transition metal hydrides is questionable. The reason for this is that many physical properties, e.g. crystalline and electronic structure, thermodynamic stability, sorption kinetics, and hydrogen diffusion are fundamentally different from transition metal hydrides. Hence, new strategies and concepts are required.

In this laboratory, main emphasis is indeed laid on the investigation of novel complex hydride systems on the experimental and technical basis:

and on a theoretical basis


References:

[1] A. Züttel, A. Borgschulte and L. Schlapbach, Hydrogen as a Future Energy Carrier, Wiley-VCH Weinheim, 2008.

contact:

 

Prof. Andreas Züttel, andreas.zuettel@empa.ch

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