Based on experience, i used RDE-3A machine (ALS Co.) conductive working electrode (disk) is connected (lead connection), and motor shaft is combined in the middle. once i turned on the rotation speed switch, some reactions are happened between working disk and carbon brush . (Carbon brush is attached to upside of the motor) with the reason that all are conductive material, the reaction behavior is automatically recorded on the monitor with software (Neo company)

when i operate with changing from 400 rpm to 1600rpm, the reaction‘s current desnsity is increased. 2000 rpm was also possible to record but when i monitored more than 1600 rpm, it looks technically dangerous.. because coated catalyst may easily detached from glassy carbon electrode of RDE.. and when i was founding OER, ORR realted paper, experimental data with more than 1600 rpm is rarely seen. i thought the reason of changing of roation speed is checking for electron transfer number..

please understand that this is not a clear answer as it is one of the reasons i am also curious

Dear Hong Jun Hyung,

Thank you for your clear answer and time.