Phase‐Engineering and Interfacial Coupling in 3D Hierarchical WO 3‐x @1T‐WS ₂ /1T(2H)‐WSe ₂ Nanoscrew Heterostructures by Plasma‐Assisted Sulfurization and Selenization Processes for Enhanced Electrochemical Hydrogen Evolution

Designing efficient and scalable electrocatalysts for the hydrogen evolution reaction (HER) remains critical to advancing sustainable hydrogen production. Here, we report tunable phase engineering and interfacial coupling in 3D hierarchical WO 3 − x @1T‐WS 2 /1T(2H)‐WSe 2 nanoscrew heterostructures synthesized via glancing angle deposition (GLAD), followed by sequential plasma‐assisted sulfurization and selenization processes. This hierarchical 3D heterostructure integrates a conductive WO 3‐x core with sequential 1T‐WS 2 and WSe 2 shells, enabling an enlarged electrochemically accessible surface area and enhanced accessibility to edge/defect‐rich catalytic regions, along with favorable phase interfaces and charge‐transport pathways. The resulting electrocatalyst demonstrates excellent HER performance in both acidic and alkaline media, with low onset potentials (−86 and −194 mV at 2 mA cm − 2 in 0.5 m H 2 SO 4 and 0.5 m KOH, respectively), small Tafel slopes (46 mV dec − 1 in acid, 73.3 mV dec − 1 in base), and remarkable operational stability over 24 h. Electrochemical analyses reveal that synergistic interfacial interactions and an optimized shell‐phase composition are pivotal for facilitating fast reaction kinetics and achieving ∼100% faradaic efficiency for the HER. These findings establish WO 3‐x @1T‐WS 2 /WSe 2 nanoscrew heterostructures as a promising platform for next‐generation water‐splitting technologies, highlighting the potential of phase‐tuned heterostructures for efficient production of green hydrogen.