If the reaction is a simple electron transfer reaction, the peaks should remain symmetrical at fast scan rates. A peak separation is observed when the scan rate , where  is the exchange electron transfer rate constant in Butler Volmer theory. Laviron equation predicts that at fast scan rates, the peaks separate in proportion to . The larger  or the smaller , the larger the peak separation. The peak potentials are , as shown by lines in fig 2B ( is the charge transfer coefficient). Examining the experimental change in peak position against scan rate therefore informs on the rate of interfacial electron transfer .