Reaction pathway analysis and reaction intermediate detection via simultaneous differential electrochemical mass spectrometry ( DEMS ) and attenuated total reflection fourier transform infrared spectroscopy ( ATR ‐ FTIRS )

Abstract A newly developed hyphenated technique, the combination of in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIRS), on‐line differential electrochemical mass spectrometry (DEMS), and electrochemical flow‐cell measurements, is described and its potential for studies of electrocatalytic reactions relevant for fuel cell operation is outlined. This method allows the simultaneous detection of adsorbed reaction intermediates ( in situ ATR‐FTIRS), volatile reaction products (on‐line DEMS), and the total Faradaic current (electrochemical measurements) at the same time, in a single experiment, under enforced and controlled electrolyte transport conditions. It also allows us to follow the adsorption process in electrolyte‐exchange transients at constant potential, which is important for kinetic studies. The potential of this method is illustrated in different examples. CO uptake transients from the CO‐containing electrolyte show the influence of the potential on the CO adsorption kinetics. Using isotope‐labeled CO, similar information can be obtained on CO ad exchange, demonstrating rapid exchange for CO adsorbed on Pt even at room temperature. Adsorption/oxidation transients and potentiodynamic measurements of the oxidation of C 1 and C 2 molecules are presented and discussed, which illustrate the potential of this method for determining the dynamics, kinetics, and mechanism of the adsorption and oxidation of small organic molecules, by combining parallel information on the contributions of different reaction pathways (product analysis) and adsorbed reaction intermediates at different stages of the adsorption/reaction process and under different reaction conditions. Finally, future developments and prospects of this method are outlined.