Energy conversion Challenges in the development of electrocatalysts
Three chemical reactions would be particularly suitable for energy conversion: the electrolysis of water to hydrogen and oxygen, which can later be used to generate electrical energy in fuel cells; the conversion of nitrogen into ammonia, an important starting material for the chemical industry; and the electrochemical conversion of CO2 into other starting materials for industry, such as ethylene.
Activity, selectivity and stability of catalysts
In their review article, the authors from the University Alliance Ruhr (UA Ruhr), describe that research on new catalysts must always keep three factors in mind: activity, selectivity and stability. Activity describes how powerful a catalyst is at a given energy input. Selectivity is defined as the ability to produce the desired substance without contaminating by-products. The stability indicates how efficient a catalyst is in the long run.
“Many publications claim high activity, stability and selectivity of electrocatalysts for important energy conversion reactions, but there is a lack of evidence”, says Wolfgang Schuhmann, head of the Centre for Electrochemistry and member of the Ruhr Explores Solvation Cluster of Excellence, Resolv (solvation.de).
Gap between basic research and application
Masa, Andronescu and Schuhmann criticize, among other things, that often not enough importance is attached to the stability of catalysts. “The underestimation of catalyst stability is largely responsible for the huge gap between seemingly exciting breakthroughs in the design of active catalysts and the practical implementation of such catalysts in technical applications,” they write.
The team identifies five factors that hinder the step from research to practice:
- The performance and material properties of catalysts under application-relevant conditions differ from those under laboratory conditions.
- There are no defined guidelines for assessing and comparing the performance of catalysts.
- Unsuitable characterisation methods are often used to determine the performance of electrocatalytic reactions.
- Too little is known about the active centres of the catalysts and their long-term stability. For example, influences of the surrounding solvent molecules and ions on the function are neglected.
- To determine the activity of a catalyst, its actual surface area must be known. Nanoparticle ensembles are often used as catalysts for which conventional methods of surface determination are not suitable
In their article, Justus Masa, Corina Andronescu and Wolfgang Schuhmann use experimental results to demonstrate how important it is to always think about the stability of catalysts in an integrated way with their activity.
Original Publication: Justus Masa, Corina Andronescu, Wolfgang Schuhmann: Electrocatalysis as the nexus for sustainable renewable energy. The Gordian knot of activity, stability, and selectivity, Angewandte Chemie International Edition, 2020, DOI: 10.1002/anie.202007672
Prof. Dr. Corina Andronescu, Technical Chemistry III, email@example.com
Prof. Dr. Wolfgang Schuhmann, Analytische Chemie (Ruhr-Universität Bochum), Tel. 0234/32 2620, firstname.lastname@example.org
Editor: Dr. Julia Weiler (RUB)