Harnessing the energy from hot charge carriers is an emerging research area with the potential to improve energy conversion technologies. This thesis present a novel plasmonic photoelectrode architecture carefully designed to drive photocatalytic reactions by efficient, non-radiative plasmon decay into hot carriers. In contrast to past work, our architecture does not utilize a Schottky junction – the commonly used building block to collect hot carriers. Instead, we observed large photocurrents from a Schottky-free junction due to direct hot electron injection from plasmonic gold nanoparticles into the reactant species upon plasmon decay. The key ingredients of our approach are (i) an architecture for increased light absorption inspired by optical impedance matching concepts (ii) carrier separation by a selective transport layer and (iii) efficient hot-carrier generation and injection from small plasmonic Au nanoparticles with heterogeneous particle size distribution to adsorbed water molecules. Also, the quantum efficiency of hot electron injection for different particle diameters has been investigated to elucidate potential quantum effects while keeping the plasmon resonance frequency unchanged.

This thesis also present a simple strategy to prepare free-standing through-hole ultrathin alumina membranes (UTAMs) for efficient sub-100 nm nanoarray fabrication that, in contrast to past works, can be generalized to any substrate and material. The potential of developed strategy for nanoarray fabrication has been demonstrated through fabrication of centimeter-scale of dense plasmonic nanoarray of sub-100 nm nanodots on very susceptible and rough substrates. Subsequently, the fabricated nanoarray has been employed for direct plasmon-driven photoelectrocatalysis of water.