In my opinion the traditional way of characterizing the catalyst by RDE is very useful for quick testing of the catalyst activity and should be done before evaluating the catalyst in the GDE. If your catalyst is promising and you want it in a real system where a gas phase is involved, mass transport (protons, electrons, oxygen, water...) is as important. We developed a GDE setup to benchmark the oxgen reduction activity, which can also be used for other setups. The main advantage compared to the floating setup is the simplicity of the cell. The testing and building of the cell is as quick as with the RDE. You can either use it with or without membrane, humidification, Nafion spraying,...

For further information you can look up our paper Article Benchmarking high surface area electrocatalysts in a gas dif...

or http://www.gde-cell.com

The disadvantage compared to RDE is of course that not only catalyst kinetic activity is involved but also other reaction limiting transport factors. So the GDE is not a good method to measure your kinetic activity, but good to measure your realistic activity. It is designed for fast testing of catalyst layer systems while adjusting the catalyst layer chemistry. This will speed up the development of new catalyst layer in the real application.

Dear Gustav, I understand you! However, I remember testing different electrocatalysts directly. This is because, I had everything to make the membrane assembly.

I do not understand why the obvious application (burning hydrogen) is not mentioned in the question. All the development of GDE is becasue of the potential use of fuel cells in cars....!

Well, nowadays the GDE can also be used for conversion of CO2 or N2 to useful chemicals. Also the oxygen reduction is not only important for the fuel cell but also for example for the Chlor-electrolysis where the cathodic site reaction is now sometimes the consumption and reduction of oxygen to actually avoid hydrogen formation.