Defect-enhanced interface polarization in Mo ₂ N/MoO ₃ heterostructures for efficient alkaline hydrogen evolution reaction and coupled power generation

Abstract Deciphering how lattice mismatch-induced vacancies enhance heterointerface catalytic activity remains a critical yet challenging frontier in heterojunction catalyst design. Herein, we constructed a defect-rich Mo 2 N/MoO 3 heterostructure embedded in a nitrogen-doped carbon matrix (Mo 2 N/MoO 3 @NC-30) via the in situ controllable oxidation of Mo 2 N@NC. In the Mo 2 N/MoO 3 heterojunction, interfacial defects are introduced by utilizing the lattice mismatch between the two materials to enhance interface polarization, thereby triggering strong charge transfer from Mo 2 N to MoO 3 and optimizing the interfacial charge distribution. Systematic experimental and theoretical investigations reveal that interfacial vacancy in Mo 2 N/MoO 3 heterojunctions could induce interfacial electron delocalization and accumulation and optimize water/intermediate adsorption/desorption, boosting catalytic activity and stability. The fabricated Mo 2 N/MoO 3 @NC-30 heterojunction catalyst exhibits exceptional hydrogen evolution reaction performance in 1.0 M KOH, maintaining remarkable stability exceeding 1000 h at −500 mA cm −2 , surpassing commercial 20 wt% Pt/C in high-current-density regimes. Additionally, a Zn–H 2 O battery incorporating Mo 2 N/MoO 3 @NC-30 as the cathode is developed for simultaneous hydrogen generation and electricity production. The system delivers a maximum power density of 10.9 mW cm −2 and maintains stable discharge performance over 70 h. This study not only advances the mechanistic understanding of vacancy-mediated interface enhancement in heterostructural catalysts, but also provides a way to the design of decoupled water electrolysis devices.