Large scale compatible fabrication of gold capped titanium dioxide nanoantennas using a shadowing effect for photoelectrochemical water splitting

Abstract

In this paper, a visible light driven plasmonic based photoelectrochemical water splitting (PEC-WS) cell is designed with an elegant two-step fabrication route. First, titanium dioxide (TiO2) nanowires (NWs) were synthesized using the hydrothermal method. Then, angled deposition was used to selectively coat the tips of the NWs yielding Au-capped TiO2 NWs with multiple sizes and shapes. The provided randomness leads to a multi-resonant system where the superposition of these resonance modes leads to an overall broadband absorption. The excited localized surface resonance (LSPR) modes contribute to the performance enhancement of the cell via near field effects and a hot electron injection mechanism. Moreover, these nanotips can trigger the formation of Fabry-Pérot (FP) cavity modes. The combination of the above-mentioned mechanisms leads to a high performance visible light driven plasmonic cell. At an applied potential of 1.23 V vs RHE, a photocurrent value as high as 82 μA/cm2 is acquired for the plasmonic based photoanode. The proposed design strategy is a large scale compatible route with no material restriction. Therefore, vast variety of semiconductor-metal pairs can be fabricated to obtain highly efficient water splitting cell for hydrogen generation.