Quadrupolar Response of Plasmonic Photocathode Fabricated by Coating Electrodeposited Ag Nanoparticles with TiO₂ (Supporting Information)

<div>Photoelectrodes based on plasmon-induced charge separation (PICS) often consist of Au nanoparticles (NPs) supported on an n-type semiconductor electrode and work as photoanodes. Meanwhile, there are fewer studies on plasmonic photocathodes fabricated by coating a plasmonic NP-modified electrode with the semiconductor. In the present study, plasmonic photocathodes in which Ag NPs electrodeposited on an indium tin oxide (ITO) electrode are covered with TiO₂ (ITO/Ag/TiO₂) were fabricated via a spray pyrolysis method. The photocathode exhibited efficient absorption and photocurrent responses derived from quadrupolar localized surface plasmon resonance (LSPR) mode. Since there are few studies on ITO/Ag/TiO₂ photocathode and the quadrupole mode shows a smaller scattering/extinction ratio and longer lifetime than the dipolar mode, the insights obtained in the present study would lead to the design of highly efficient plasmonic photocathodes.</div>