The sufficient utilization of Mott–Schottky effect for boosting alkaline hydrogen evolution reaction (HER) depends upon scale minimizing of interface components and exposure maximizing of Mott–Schottky interface. Here, a self-standing porous tubular Mott–Schottky electrocatalyst is constructed by a self-template etching strategy, where amorphous WO_x (a-WO_x) nano-matrix connects Co nanoparticles. This novel “Janus” electrocatalyst maximizes the Mott–Schottky effect by not only providing a highly exposed micro interface, but also simultaneously accelerating the water dissociation and optimizing the hydrogen desorption process. Experimental findings and theoretical calculations reveal that Co/a-WO_x Mott–Schottky heterointerface triggers the electron redistribution and a build-in electric field, which can not only optimize the adsorption energy of the reaction intermediates, but also facilitate the charge transfer. Thus, Co/a-WO_x requires an overpotential of only 36.3 mV at 10 mA·cm⁻² and shows a small Tafel slope of 53.9 mV·dec⁻¹ as well as an excellent 200-h long-term stability. This work provides a novel design strategy for maximizing the Mott–Schottky effect on promoting alkaline HER.