Boosting electrocatalytic activities of plasmonic metallic nanostructures by tuning the kinetic pre-exponential factor

•Controllable synthesis of ultrathin Pd NRs with tunable length and a tunable SPR.•The ORR activity can be improved by an increase of the apparent pre-exponential factor.•The enhancement of the proton tunneling contribution upon SPR excitation is verified.•Such plasmon-enhanced electrocatalysis is universal to the proton-coupled reactions.