Abstract
We successfully conducted electrochemical and online mass spectrometric measurements on commercial carbon felt electrodes with a differential electrochemical spectrometry setup. Its capability is demonstrated by simultaneous mass spectrometric and electrochemical measurements. Half-cell tests, such as cyclic voltammetry, and coulometry of the redox couples can be performed under stopped flow of the electrolyte. We use different potential windows, and two types of electrolytes while monitoring potential dependent H2, O2 and CO2 formation. At oxidizing potentials, we did not observe oxygen evolution, only carbon corrosion. An increase in CO2 and H2 formation at high and low potentials in the presence of vanadium is observed.
Highlights
Carbon fibers in the form of paper or felts are the most common electrode material for vanadium redox flow batteries (VRFBs)
Differential electrochemical spectrometry (DEMS) has been proven to be suitable characterizing carbon materials, mainly in the context of fuel cell research.[3−5] Recently, Taylor et al used DEMS to calculate the faradaic efficiency of the V3+ reduction reaction on the oxidized edge and basal surfaces of graphite discs in a model study on the activity and stability of the negative electrode in VRFBs.[6]
In this study we present a modification of a DEMS flow cell,[7] which enables mounting of the commercial carbon felts as a working electrode for conducting simultaneous electrochemical and online mass spectrometric experiments
Summary
Letter this potential range, as expected and evidenced by both flow and stopped flow measurements. Its peak current is significantly higher compared to the V4+ oxidation to V5+ when applying the low potential limit of 0.0 V (Figure 1b), whereas the reduction peak of V5+ to V4+ is similar, irrespective of the lower potential limit, which would be expected for the same amount of vanadium trapped in the confined space. By comparing the electrochemical behavior in sulfuric acid base electrolyte and in vanadium containing electrolyte, we demonstrated that the presence of vanadium ions has a profound effect, leading to 50% higher CO2 formation and a lower onset potential in the oxidative potential regions This implies that the previously oxidized V5+ acts as an oxidizing agent versus the carbon electrode.
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