The development of innovative new methods is an essential component of our research, since new methods can bring new insights.
In this direction, we have developed the electrochemical real-time mass spectrometry (EC-RTMS): A novel, powerful technique which enables the time- and potential-resolved characterization of electrochemical reaction products, either gases or liquids, shortly after their formation. This internationally unique methodology provides information about processes that occur at short timescales at dynamic electrochemical interfaces, which can guide to the design of new, robust catalysts for selective electrosynthesis. We have demonstrated the capabilities of the method for a few classical electrochemical reactions, like the electrochemical reduction of CO2 on copper or the oxidation of C1-C3 alcohols on platinum, in which the reaction products were determined in real time.
EC-RTMS is based on the combination of two individual mass spectrometry techniques, after proper modification of their inlets. The electrolyte that contains the products of electrode reactions is withdrawn continuously for analysis, using a thin capillary which is positioned very close to the working electrode surface. Gaseous products are extracted from the electrolyte stream using a home-constructed degasser, which consists of a hydrophobic membrane placed into a gas-tight chamber. The chamber is connected to an electron ionization - quadrupole mass spectrometer (EI-QMS) for analysis of the extracted gases. Rapid gas extraction is enabled by the large pressure difference between the ambient conditions at the electrolyte-side of the membrane, and the vacuum at the back side connected to the mass spectrometer. The degassed electrolyte that exits the degasser is nebulized using a gas of high flow rate, and a spray chamber separates the fine mist for analysis, while large droplets are directed to waste. The composition of the fine mist is finally analyzed with direct analysis in real-time or proton transfer reaction mass spectrometry (DART-TOF-MS or PTR-TOF-MS).
The development of EC-RTMS will accelerate the design of robust interfaces for novel electrosynthesis processes, by having major impacts on:
- the quick assessment of the potential-dependent product distribution at various electrode-electrolyte interfaces
- mechanistic studies on reaction pathways of complex electrochemical reactions by monitoring the formation of intermediate and final products
- capturing transients in product formation which are imposed by dynamic conditions relevant to future energy conversion applications, and are otherwise not accessible with classical methods.
Details on the instruments used in EC-RTMS can be found here.