Electrochemical Energy Group

The research activities in the group include photo-electrochemical research, fuel cells, and water electrolysis. These research areas are related to the needs for a sustainable energy system based on renewable energy.

Today’s general concern for the problems inflicted upon the global climate through CO₂ emissions by the current extensive use of fossil fuels as well as fossil resource issues has led to an intensive search for alternative energy systems, primarily based on nuclear or renewable energy sources (http://www.iea.org). Energy storage remains a major challenge associated with wide-scale deployment of renewable energy. It is therefore anticipated that electrochemical energy storage, such as represented by batteries or energy systems based on hydrogen as a storage medium, will play a central role in peak-levelling renewable energy production.

In a hydrogen energy-system water electrolysers and fuel cells are devices of critical importance. In both of these, a non-trivial part of the design is related to the electron transfer at interfaces between electronic and ionic conductors. If the rate of the electron transfer is dependent on the chemical composition of the electronic conductor or on its surface microstructure, the process is said to be electrocatalytic, and the electrode is referred to as an electrocatalyst.

In many electrochemical energy conversion systems the process that takes place at the interface between the catalytic material involves also a gas phase in addition to the liquid and solid phases, and optimisation of structures with respect to maximisation of this so-called three-phase boundary becomes important. For some fuel cell reactions platinum and some of its alloys are preferred electrocatalyst and for the cathode process in water electrolysis. The anode process in water electrolysis usually employs transition metal oxides as the electrocatalyst.

The requirement of the highest possible surface area usually dictates the use of porous electrodes in which the catalyst is present in the form of nano-sized particles, and frequently the electrocatalyst is deposited on a catalyst support. The support material has to be an electronic conductor and corrosion resistant in the given environment, and hence carbon is often used. The function of the support is primarily to stabilise the catalyst particles, which otherwise would coalesce, dissolve, or undergo Ostwald ripening (dissolution-precipitation growth of larger particles at the expense of the smaller ones) due to the large surface area (beneficial for catalyst activity but detrimental to stability due to high surface energy).

For some catalyst-support systems, notably those employing oxides as support material, the presence of strong metal-support interaction (SMSI) can make the support influence the catalyst beyond stability, imparting enhanced activity to the catalyst. Some reports indicate that this may also be the case for Pt-carbon systems, although the evidence so far may not be considered conclusive. There are still some unresolved questions concerning the effects of the support material with respect to the activity of the prepared electrocatalysts. Results presented in the literature may indicate that the catalytic activity for nanoparticles supported on carbon is different from that of the unsupported particles. However, it is still not clear whether there is a electronic metal-support interaction between the platinum particles and the substrate, or if the role of the support is solely to ensure an advantageous particle dispersion or shape.