Interfacial Phonon Thermal Transport Properties of Semiconductor Composite Electrodes with Plasmonic metal

Plasmonic solar water splitting is based on the composite electrode incorporating plasmonic metal nanoparticles on semiconductor, where the localized heating generated by relaxation of the metal's localized surface plasmon resonance (LSPR) under light excitation enhances hydrogen production efficiency. To optimize composite photoanodes for photoelectrochemical water splitting system, this study employs non-equilibrium molecular dynamics simulations to calculate the interfacial thermal conductivity between plasmonic metals (Cu, Ag, Au) and semiconductors (TiO₂, ZnO, MoS₂) across varying temperatures. The relationship between interfacial thermal conductivity and phonons of different frequencies was investigated via vibrational density of states which was calculated from the velocity autocorrelation functions and subsequent phonon participation ratio. The results indicate that the interfacial thermal conductivity across all composite electrode configurations enhance with the increase of temperature. When paired with TiO₂, the thermal transport performances in Cu-TiO₂ and Ag-TiO₂ are superior to that of Au-TiO₂, and the interfacial thermal conductivity of Cu-TiO₂ reaches 973.56 MW m⁻²·K⁻¹ at 800 K. With Au as the fixed plasmonic component, Au-ZnO demonstrates the higher interfacial thermal conductivity over Au-MoS₂ and Au-TiO₂, showing 324.44 MW m⁻² K⁻¹ at 800 K. Based on the obtained interfacial thermal conductivities of different composite photoanodes, Cu-ZnO is predicted as optimal composite, but its interfacial thermal conductivity of 547.69 MW m⁻² K⁻¹ at 800 K ranks second only to Cu-TiO₂. The analysis of vibrational density of states and phonon participation ratio reveal the low-frequency region (0-10 THz) as dominant for thermal transport, with both interfaces exhibiting the high phonon participation ratio range of 0.7-0.8. However, Cu-TiO₂ possesses significantly higher vibrational density of states than Cu-ZnO within this critical band. Although Cu-ZnO shows higher phonon participation ratio range in the high-frequency range, its lower overall interfacial thermal conductivity is attributed to the minimal contribution of high-frequency phonons to interfacial thermal conductance. The findings provide optimization strategies based on interfacial thermal transport mechanisms for constructing efficient photoanodes for solar water splitting.