Herein, we advance our fundamental understanding of hydrogen electrochemistry as crucial energy technology by challenging the century-long paradigm that Volmer, Heyrovsky, and Tafel reactions are elementary. We identify and resolve the theoretical controversy of this phenomenological model to argue that each reaction must be stepwise not concerted elementarily. The stepwise model provides unprecedented insights as exemplified by resolving current debates on the Tafel analysis and volcano plot based on the controversial concerted model. The stepwise mechanism has not been distinguished from the concerted mechanism experimentally owing to the Laviron–Amatore paradox, which will be overcome by developing transient nanoelectrochemical methods.