The rectification effect in Schottky heterojunctions plays a crucial role in modulating electrocatalytic activity, yet precise control over electron transfer to optimize the rectification effect and accelerate catalytic kinetics remains challenging. Herein, we construct a Schottky heterojunction with tunable rectification effect by anchoring ultrafine PtCu alloy nanoparticles on the surface of WO_x supports (PtCu/WO_x) via surface segregation and galvanic replacement reaction. The increased W⁵⁺/W⁶⁺ ratio enlarges the work function difference, driving intense electron transfer at the interface. Kelvin probe force microscopy and zeta potential analysis visualize and quantify the built-in electric field intensity induced by the rectification effect, establishing a volcano relationship correlation with oxygen reduction reaction (ORR) kinetics. Besides, the abundant oxygen vacancies in WO_x support facilitate the adsorption of oxygen on PtCu. The optimized PtCu/WO_x-350 with a moderate electron transfer presents the fastest ORR kinetic process. This work explores the correlation between rectification effects and ORR kinetics, offering insights into the rational design of Schottky heterojunctions, elucidating the interface charge transfer mechanism, and enhancing the electrocatalytic performance.