Comparing the first potential cycles recorded with the different batches, reveals significant differences in the electrochemical behaviour of the individual batches. Nevertheless, the behaviour of batches 1 and 3 (Figures and), as well as that of batches 2 and 4 (Figure and), are rather similar and are henceforth denoted as type I (left column) and type II (right Specifically, the CVs for type I show three distinct peaks, i.e., in the negative-going scan peaks C1 (-0.45 V) and C3 (-0.9 V), and in the positive-going scan peak A1 (0.4 V). In some measurements, an additional less pronounced peak A2 is observed at -0.5 V in the positivegoing scan. In the case of type II, the current density in the CVs is much lower compared to that in the CVs with type I. For comparison and visibility of the features a CV re-scaled with a factor of five is shown as a grey curve in Figures 2b and d. In the CVs with type II, additional peaks can be observed in the negativegoing scan direction, i.e., peaks C2 (-0.6 V) and C4 (-1.4 V). In the positive-going scan, peak A2 (-0.5 V) is more pronounced and observed in every measurement. The peaks C1 and A1 from type I are still clearly visible, even though the current density of the peaks is about five times lower. The intensity of peak C3 from type I is also much lower and it is not well resolved.