To investigate CCM degradation using lab-based μ-CT the ME-cell was imaged before and after a stability test (detailed methodology provided in Section 4). A stability test was also performed in the LE-cell using a nominally identical CCM for comparison. An increase in Ecell,iR corr. was observed for both the ME and LE-cells (up to ≈ 100 and 60 mV for the ME and LE-cell, respectively) over each of the 2 h current hold cycles (Figure ). Then, following each hold period at open circuit potential (OCP), the majority of the voltage increase was recovered. This recoverable voltage increase may be caused by the accumulation of H2 and O2 gas in the cell during operation. When the cell was switched to OCP under continuous flow of feed solution, H2 and O2 were likely washed out; this is reflected as a reduction in in Ecell,iR corr. when current is applied again.