New double-band-electrode channel flow differential electrochemical mass spectrometry cell: application for detecting product formation during methanol electrooxidation.

We present a new double-band-electrode channel flow DEMS (differential electrochemical mass spectrometry) cell and demonstrate its application in mechanistic studies with particular relevance to fuel cells. The cell is composed of two band electrodes, which serve as working and detecting electrodes, respectively, separated by a porous Teflon membrane. The Teflon membrane serves as the interface between the aqueous solution and vacuum, through which gases and volatile species can be transported. The hydrodynamic electrochemical characteristics and mass spectrometric behavior have been characterized. With this DEMS cell, gaseous and volatile electrochemical products formed at the working electrode are monitored by mass spectrometry, while nonvolatile products can be selectively detected at the detecting (downstream) electrode. Thus, this system can be considered as the DEMS analogue of a rotating ring/disk electrode. As test cases, the electrooxidation of formaldehyde and methanol on carbon supported Pt nanoparticle catalysts have been studied using this new channel flow DEMS cell.