Ti₂CO₂/ZrSi₂N₄: A promising van der Waals heterostructure for advanced thermoelectrics and efficient hydrogen evolution reaction

With the expeditious increase in global energy demand and consequent consumption of natural resources, there is an urgent need for alternative, efficient, and economically viable energy harvesting technologies. For this purpose, we have explored the Ti₂CO₂/ZrSi₂N₄ van der Waals heterostructure (vdWH) exhibiting a minimal lattice mismatch of approximately ∼0.1 %, suggesting excellent interfacial compatibility between the constituent layers. The omission of imaginary phonon frequencies all over the Brillouin zone confirms the dynamical resilience of the Ti₂CO₂/ZrSi₂N₄ vdWH. The considered vdWH possesses an indirect band gap of 0.91 eV by the Heyd−Scuseria−Ernzerhof functional level with spin-orbit coupling (SOC) effect. Moreover, the vdWH exhibits an optical absorption coefficient of 3 × 10⁵ cm⁻¹ within the visible spectrum, alongside significant optical absorption extending to the ultraviolet (UV) range. The calculated limited maximum efficiency (SLME) of heterostructure is approximately 31.6 % which is higher than any other thin-layer absorbing materials, including CsGeI₃ (∼30.5 %), CsPbI₃ (27.6 %), Ca₂Si (∼31.2 %), and CuInS₂ (29 %). demonstrates its suitability as a next-generation photovoltaic absorber. The calculated figure of merit ZT of 0.7 at an n-type carrier concentration of 4.1 × 10²⁰ cm⁻³ at 500 K primarily results from the enhanced thermal power factor S²σ/τ, where τ, σ, and S represent the carrier relaxation time, electrical conductivity, and Seebeck coefficient, respectively. Our results highlight the excellent potential of the Ti₂CO₂/ZrSi₂N₄ heterostructure as a strong candidate for future catalysis, photovoltaic, and thermoelectric applications.