Effects of Surface Plasmon and Catalytic Reactions on Capacitance in Metal–Semiconductor Schottky Diodes

Capacitors, renowned for their high power and energy density attributed to their rapid discharge capabilities, hold significant promise as energy storage devices. While capacitors with various junctions have been the subject of extensive research, there remains a significant knowledge gap concerning the fundamental photoelectron dynamics within metal–semiconductor (MS) junction capacitance, which is crucial for the development of photodevices. Here, we demonstrate the effects of localized surface plasmon resonance (LSPR) on the capacitance behavior of Au/TiO₂ Schottky diodes, one of the MS junction diode systems. We have confirmed that the plasmonic Au/TiO₂ shows substantial photoresponsiveness, with an increase in net total capacitance under stronger plasmonic effects, as confirmed by wavelength- and power-dependent studies. To enhance our understanding of the electron transfer process occurring at the MS junction, we expand our investigation of capacitance within a catalytic reaction environment, specifically focusing on Pt/TiO₂ Schottky diodes. We show the catalytic environment changes capacitance values of the Pt/TiO₂, and more active catalytic reactions decrease net total capacitance due to catalytic electrons interfering with diffusion electrons. The LSPR effect and catalytic reaction significantly impact the net total capacitance with a predominant contribution associated with hot electrons, catalytic electrons, and diffusion effects. These findings provide valuable insights for designing and optimizing efficient optical and catalytic devices across diverse applications.