Interfacial Charge Engineering in TiSSe/Borophene van der Waals Heterostructures for Enhanced Quantum Capacitance and Electro-Mechanical Stability

Abstract

Two-dimensional van der Waals heterostructures offer new opportunities to tune charge redistribution, interfacial coupling, and electrochemical performance for next-generation energy-storage devices. Here, we present a detailed first-principles investigation of Janus TiSSe/honeycomb-borophene heterostructures and reveal how chalcogen-specific terminations control their structural, electronic, and quantum-capacitive behaviour. Both Se-B and S-B interfaces exhibit favourable binding energies and phonon spectra without imaginary modes, confirming thermodynamic and dynamical stability. Strong Ti-X-B (X = S, Se) hybridisation induces metallicity in both systems; however, the Se-terminated interface shows significantly higher DOS at the Fermi level, smoother band dispersion, an interconnected Fermi surface, and enhanced charge delocalisation. These features, along with lower effective mass, higher carrier mobility, and stronger dielectric screening, demonstrate the superior electronic responsiveness of TiSSe/H-Borophene. Combined with its higher electrical conductivity, lower Seebeck coefficient, and stable thermal transport, the Seterminated interface achieves an enhanced quantum capacitance of 736.15 μF cm⁻² and a maximum surface charge density of 445.88 μC cm⁻², surpassing the S-B interface. Overall, this study establishes chalcogen-selective interface engineering as an effective strategy for positioning TiSSe/H-borophene as a promising quantum-capacitance-dominated electrode for advanced nanoscale energy storage applications.