Why Fuel Cell Catalysts React Differently Than Expected

A study from Berlin shows that the activity of fuel cell catalysts does not depend on a single reaction step. This changes established models of electrocatalysis.

Researchers at the Fritz Haber Institute of the Max Planck Society have gained new fundamental insights into how catalysts work in fuel cells. According to a publication in the journal Nature Communications, several successive reaction steps influence the overall kinetics of the oxygen reduction reaction (ORR) – a key process for the efficiency of fuel cells.

The study shows that changes at the interface between the catalyst and the electrolyte play a decisive role. According to the study, the activity of the catalysts investigated cannot be attributed to a single rate-determining reaction step, as has long been assumed in electrocatalysis.

Kinetics Investigated Under Realistic Conditions

The research team systematically analyzed four different fuel cell catalysts under industrially relevant conditions. They investigated how voltage and oxygen pressure affect the reaction kinetics. The results suggest that the reaction-determining steps change with the applied overvoltage.

“The traditional view is that multistep reactions can be traced back to a single rate-determining intermediate step,” explained study author Dr. Sebastian Öner. However, this assumption does not apply to the systems investigated. Instead, catalyst activity is determined by several voltage- and pressure-dependent processes at the interface.

New Impetus for Catalyst Research

According to the researchers, the work fundamentally changes the understanding of multistep electrocatalytic reactions. The results provide a new kinetic framework for better interpreting structure- and voltage-dependent changes in catalysts, for example, using operando spectroscopy and microscopy.

Institute director Prof. Dr. Beatriz Roldán Cuenya emphasizes how important it is to systematically link chemical and structural changes at the interface with the activation parameters. In the long term, the findings could contribute to the more targeted development of catalyst materials for electrochemical energy conversion.

This is a partly automated translation of this german article.