Defects can introduce atomic structural modulation and tailor performance of materials. Herein, it demonstrates that semiconductor WO with inert electrocatalytic behavior can be activated through defect-induced tensile strains. Structural characterizations reveal that when simply treated in Ar/H atmosphere, oxygen vacancies will generate in WO and cause defective structures. Stacking faults are found in defects, thus modulating electronic structure and transforming electrocatalytic-inert WO into highly active electrocatalysts. Density functional theory (DFT) calculations are performed to calculate H adsorption energies on various WO surfaces, revealing the oxygen vacancy composition and strain predicted to optimize the catalytic activity of hydrogen evolution reaction (HER). Such defective tungsten oxides can be integrated into commercial proton exchange membrane (PEM) electrolyser with comparable performance toward Pt-based PEM. This work demonstrates defective metal oxides as promising non-noble metal catalysts for commercial PEM green-hydrogen generation.