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.

基于光谱方法的燃料电池操作诊断技术的发展对于理解分子水平的电化学过程至关重要。在传统的电解池中，在线电化学质谱（OEMS）可以通过覆盖质谱仪入口的疏水性多孔膜实时检测电化学反应期间溶液中的气态和挥发性物质。但是，OEMS尚未用于检测燃料电池催化剂层，主要是因为采样入口的尺寸较大，并且该方法分析低挥发性物质的能力很差。在此，我们开发了一种基于液体采样和汽化的液体入口OEMS方法，该方法可以有效地检测溶液中的低挥发性物质。采样毛细管很小，可以插入燃料电池催化剂层中以有效检测产物和反应物。然后将这种方法用于在操作上监测直接乙醇燃料电池中反应物乙醇以及产物乙醛和乙酸的浓度变化。