Hybrid photonic-plasmonic photoelectrode for enhanced photoelectrochemical current generation

Photoelectrochemical (PEC) reactions realized through the nonradiative decay of plasmonic process in metallic nanostructure earned tremendous potential to harvest solar irradiance. In conventional metal-semiconductor photoelectrodes, the electric field confinement using optical resonating modes is crucial to instigate plasmonic charge for enhanced photocurrent generation. However, the effect of such resonant states in a semiconductor-free plasmonic photoelectrode is limitedly explored. In this essence, we have experimentally realized a Schottky junction-free plasmonic-photonic hybrid photoelectrode consisting of one-dimensional porous grating of gold nanoparticles (GNPs) on top of a ITO waveguide. This designed photoelectrode exhibits PEC photocurrent generation solely from plasmonic hole transfer to the molecules/ions at the metal-adsorbed water interface. Spectral overlapping of plasmonic activities with photonic modes and porosity-induced large metal-electrolyte interface surface area further enhance the charge generation and transfer. In the results, the GNPs photoelectrode recorded 3.4 and 12.6-fold increases in the incident photon to electron conversion efficiency (IPCE) in contrast to conventional gold bar grating photonic crystal and random GNPs photoelectrodes, respectively. Further, modal coupling of resonant states witnesses a substantial rise in the photocurrent generation than the uncoupled resonant states. The present report delivers a facile strategy for tailoring the plasmonic photocurrent generation in futuristic solar energy harvesting applications.