Tailoring Active Sites in Mesoporous Defect‐Rich NC/Vo‐WON Heterostructure Array for Superior Electrocatalytic Hydrogen Evolution

Tailoring active sites in earth‐abundant non‐noble metal electrocatalysts are required toward widespread applications in sustainable energy fields. Herein, an integrated mesoporous heterostructure array is reported by a hydrogenation/nitridation‐induced in situ growth strategy. Highly conductive oxygen‐vacancies‐rich tungsten oxynitride (V o ‐WON) nanorod array acts as the backbone encapsulated by ultrathin nitrogen‐doped carbon (NC) nanolayers, forming high‐quality shell/core NC/V o ‐WON heterostructures. Density functional theory calculations reveal that defect‐rich heterostructure arrays not only enhance the conductivity and modulate electronic structure but also promote the adsorption and dissociation of reactants and offer substantial potential sites. As expected, porous NC/V o ‐WON array exhibits a small overpotential of 16 mV at the current density of 10 mA cm −2 and a low Tafel slope of 33 mV per decade in alkaline media, accompanied by negligible loss upon a large current density over 100 h. Benefiting from outstanding electrocatalytic hydrogen evolution reaction performance and stability, this defective heterostructure could serve as a prominent alternative electrocatalyst for renewable energy applications.