The sluggish kinetics of alkaline hydrogen evolution reaction (HER) at industrial-current densities stem from rigid interfacial water structures that impede water dissociation and hydroxyl (OH-) transfer. Here, we engineer vanadium single-atom-doped CoP (V-SA-CoP) to dynamically reconfigure hydrogen-bond networks at the catalyst-electrolyte interface. Through combined ab initio molecular dynamics and in situ Raman spectroscopy, we demonstrate that oxyphilic V Lewis acid sites disrupt ice-like water clusters, liberating free water molecules and increasing interfacial water mobility. This optimized microenvironment synergistically facilitates HO-H bond cleavage and enables rapid OH- diffusion via a K+-assisted Grotthuss mechanism, mitigating OH* poisoning while accelerating reaction kinetics. The V-SA-CoP catalyst achieves an ultralow overpotential of 266 mV at 1000 mA cm(-2) in alkaline media and sustains >300 h stability at 100 mA cm(-2), surpassing commercial Pt/C. This work deciphers the critical role of interfacial water dynamics in high-current-density electrocatalysis, providing a universal strategy for catalyst design via microenvironment control.