Developing  highly  efficient  and  cost-effective  oxygen  evolution  reaction  (OER)  electro-catalysts is critical for many energy devices. While regulating the proton-coupled electrontransfer (PCET) process via introducing additive into the system has been reported effectivein promoting OER activity, controlling the PCET process by tuning the intrinsic materialproperties  remains  a  challenging  task.  In  this  work,  we  take  double  perovskite  oxidePrBa0.5Sr0.5Co1.5Fe0.5O5+δ(PBSCF)  as  a  model  system  to  demonstrate  enhancing  OERactivity through the promotion of PCET by tuning the crystal orientation and correlatedproton diffusion. OER kinetics on PBSCF thinfilms with (100), (110), and (111) orientation,deposited  on  single  crystal  LaAlO3substrates,  were  investigated  using  electrochemicalmeasurements, density functional theory (DFT) calculations, and synchrotron-based nearambient X-ray photoelectron spectroscopy. The results clearly show that the OER activity andthe ease of deprotonation depend on orientation and follow the order of (100) > (110) > (111).Correlated with OER activity, proton diffusion is found to be the fastest in the (100)film,followed by (110) and (111)films. Our results point out a way of boosting PCET and OERactivity, which can also be successfully applied to a wide range of crucial applications in greenenergy and environment.