A novel differential electrochemical mass spectrometer (DEMS) with a stationary gas-permeable electrode in a rotational flow produced by a rotating rod

Abstract

In recent studies of electrochemistry, a variety of in situ spectroscopic analyses of intermediates and products in electrochemical reactions have been developed to clarify their mechanisms, and these have provided us with a great deal of valuabie information [l-7]. Among the spectroelectrochemical methods, the first technique combining directly a mass spectrometer and an electrochemical cell, i.e. electrochemical mass spectrometry (EMS), was developed by Bruckenstein and coworkers [8-121 more than two decades ago. Later, Heitbaum and coworkers [13-181 improved. EMS so that the variation in the amount of the species produced with respect to time or electrode potentials could be measured. They called the method differential electrochemical mass spectrometry (DEMS), where differential means time-derivative, and thus the mass intensities observed are proportional to the corresponding electrochemical currents. In contrast, the mass intensities were proportional to the charge for the electrolyses in EMS. Vielstich and coworkers [19-241 and recently Enyo and coworkers [25,26] and other groups [27-291 have been studying various electrochemical processes with DEMS and EMS. The usefulness of the method has been reviewed very recently by Bittins-Cattaneo et al. 1301. We have been studying the catalytic electrochemical reduction of CC, [31,32] with nickel cyclam [33] in connection with artificial photosynthesis with molecular assemblies [34-391. In these investigations, identification of products in situ during the cyclic voltammetric measurements has been&greatly needed because the infor-