Abstract
In situ Fourier transform infrared‐diffuse reflection spectroscopy is introduced as a method for studying the catalytic surfaces of membrane electrode assemblies in working fuel cells. An annular collection electrode and a 
window are used to expose a sufficient area of the electrode to the IR beam. Experimental results for methanol oxidation, CO adsorption, and 
adsorption show that this method can be used to monitor the catalyst surface in a direct methanol fuel cell under load. The IR peaks associated with CO adsorption on high surface area Pt‐Ru are similar to previously observed peaks on smooth electrodes reported in the literature.