Liquid-inlet online electrochemical mass spectrometry for the in operando monitoring of direct ethanol fuel cells

Abstract

Developing in operando diagnostic techniques based on spectroscopic methods for fuel cells is vital for understanding electrochemical processes at the molecular level. In a conventional electrolytic cell, online electrochemical mass spectrometry (OEMS) can detect in real time gaseous and volatile species from solution during electrochemical reactions through a hydrophobic porous film covering the mass-spectrometer inlet. However, OEMS has not been used to detect fuel-cell catalyst layers mainly because of the large size of the sampling inlet and the method's poor ability to analyze low-volatility species. Herein, we developed a liquid-inlet OEMS method based on liquid sampling and vaporization that can effectively detect low-volatility species from solution. The sampling capillary was small and can be inserted into a fuel-cell catalyst layer to detect products and reactants effectively. This method was then used in the in operando monitoring of concentration variations of the reactant ethanol and the products acetaldehyde and acetic acid in a direct ethanol fuel cell.