In situ differential electrochemical mass spectrometry (DEMS)

In-situ differential electrochemical mass spectrometer (DEMS) is an electrochemical reaction cell coupled with a mass spectrometer. It can detect gases and volatile intermediates and final products consumed or produced at the electrochemical reaction interface in real time, and conduct qualitative and quantitative analysis. Analytical instruments.DEMS can detect trace amounts of gas produced or consumed during the reaction within milliseconds and is an important tool for studying electrochemical reaction mechanisms and evaluating electrochemical reaction performance.

The developed DEMS is divided into two parts: sampling system and detection system.

Detection system details

Sample injection system details

Battery DEMS Application Overview

DEMS can be used for real-time monitoring of gas consumption and generation during battery charging and discharging. During testing, the gas flow is precisely controlled through the sampling system, the gas is sent into the reactor for reaction, and the post-reaction gas is collected and condensed in a cold trap to remove the electrolyte brought out. , and finally enter the detection system for detection.According to different battery types, corresponding reactors can be customized.

Soft pack battery reactor

Button cell reactor

Applications:

Li-O2 battery charging and discharging process O2 detection 1

DEMS is used to monitor O2 consumption and precipitation during charging and discharging of Li-O2 batteries, and quantitatively analyze the Faradaic effect of battery charging and discharging (ACS Appl Mater Interfaces 13, 28295-28303).

Sodium ion soft pack battery gas production detection

DEMS is used to monitor the first cycle of charge and discharge of sodium-ion soft pack batteries. The main side reaction gases are CO2, CH4, and H2, and trace amounts of C2H4 can be detected.

Lithium-ion battery electrolyte decomposition detection

DEMS is used to monitor the decomposition of lithium-ion battery electrolytes. The main side reaction gases are H2 and CO2.

Lithium metal button battery

DEMS is used to monitor the first cycle charging of LFP||Cu batteries with no negative electrode structure. The main side reaction gases are H2 and CO2

Overview of electrocatalytic DEMS applications

In electrocatalytic reactions, exploring the local reaction environment, especially the interface between the electrode and the electrolyte and the hydrodynamic boundary layer near the cathode, plays a crucial role in judging the activity and selectivity of the reaction and explaining the reaction mechanism.DEMS can rely on the vacuum pressure difference to extract the reaction gas products at the interface into the mass spectrometer, thereby achieving highly sensitive and high-resolution product detection.

Application cases (the following cases are derived from scientific literature and are only for popular science promotion and are not the results of our products):

Explore the effect on gas products when Cu catalyst supports different ionomer layers

DEMS can respond to changes in the reaction system with millisecond time resolution, so it is often combined with potential scanning methods to observe the transient evolution of products at different potentials to reveal the impact of different ionomer layers on local pH values.

During the cathode and anode potential scans, the local pH value of the catalyst surface may be different, resulting in different distribution of reaction products.This study used DEMS to monitor the formation of H2, CH4, and C2H4 during cyclic voltammetry. The results showed that when loading different ionomer layers, the formation of the above gas products showed different degrees during the anode scan compared to the cathode scan. Increase or decrease, from which the effect of different ionomer layers on local pH can be inferred (Bell et al. Nature Energy 6, 1026-1034).

2. Real-time analysis of pulse electrochemical reduction products 3

Pulse electrochemistry involves the impact of multiple potential changes on catalytic products. The use of DEMS can reflect the real-time changes in catalytic products with potential changes, which is of great help for monitoring the reaction process and exploring the pulse electrochemical reaction mechanism.

DEMS combined with potential scanning voltammetry reflects the changes in the accumulation degree of different products on the catalyst surface with potential, thereby determining the appropriate cathode periodic potential.At the same time, DEMS is combined with step timing amperometric measurement and the product signal value is normalized, which intuitively reflects the change of the local concentration of the product over time, thereby determining the duration of the pulse potential.

The real-time mass signal corresponding to CO2 and the electroreduction reaction gas product during the pulse process is detected by DEMS.At the same time, the comparison of DEMS signals at different pulse cycle periods shows that the adsorption concentration of CO on the catalyst surface increases with the extension of pulse electrolysis time (Bell et al. ACS Catalysis 10, 12403-12413).

1 Wei, L. et al. Ru-Embedded Highly Porous Carbon Nanocubes Derived from Metal-Organic Frameworks for Catalyzing Reversible Li2O2 Formation. ACS Appl Mater Interfaces 13, 28295-28303, doi:10.1021/acsami.1c06572 (2021).

2 Kim, C. et al. Tailored catalyst microenvironments for CO2 electroreduction to multicarbon products on copper using bilayer ionomer coatings. Nature Energy 6, 1026-1034, doi:10.1038/s41560-021-00920-8 (2021).

3 Kim, C. et al. Impact of Pulsed Electrochemical Reduction of CO2 on the Formation of C2+ Products over Cu. ACS Catalysis 10, 12403-12413, doi:10.1021/acscatal.0c02915 (2020).