Dual-active-site strategies are widely adopted to address the intrinsic challenge of simultaneously promoting water dissociation and maintaining an optimal hydrogen adsorption free energy in alkaline hydrogen evolution. However, this paradigm implicitly presumes rapid equilibration of hydrogen intermediates (H*), thereby neglecting H* transport as a fundamental kinetic bottleneck. Here, we show that rational regulation of interfacial hydrogen-spillover pathways offers an effective kinetic lever for modulating alkaline hydrogen evolution. An atomically coupled Pt-Co₃O₄ heterostructure, featuring Pt nanoparticles anchored on Co₃O₄ nanowire arrays, is constructed as a model system. We reveal that interfacial electron transfer generates a built-in electric field, which can be effectively tuned via oxygen-vacancy-mediated modulation of the work function difference, thereby enabling controllable regulation of interfacial H* migration. This field drives a reverse hydrogen spillover process and lowers the H* migration barrier to 0.13 eV, transforming the heterointerface into a high-efficiency H* transport channel. Enabled by this field-regulated reaction pathway, the catalyst delivers an overpotential of 18.7 mV at 10 mA·cm^–2 and a Tafel slope of 27.8 mV·dec^–1 in 1.0 M KOH. The practical relevance is validated by alkaline seawater electrolysis, delivering 1.0 A·cm^–2 at 1.76 V and maintaining stable performance for over 500 h. This research clarifies the electronic origin of accelerated reverse hydrogen spillover and offers a universal design paradigm for high-performance multi-step electrocatalysis.