TiO2/Au Nanoring/p-Si Nanohole Photocathode for Hydrogen Generation

Nowadays, numerous electrochemical and photoelectrochemical (PEC) methods have been utilized for water-splitting hydrogen production. Herein, we designed a novel photocathode based on a TiO2/Au nanoring (AuNR)/Si nanohole (SiNH) hetero-nanostructure (HN), which can be fabricated in a programmable way. The SiNH arrays substrate was prepared by nanoimprint lithography, and then, embedded AuNRs were fabricated by sputtering deposition and subsequent ion beam etching to remove the Au layer covering the horizontal Si surface. Cylindrical AuNRs clinging to the sidewalls of SiNH arrays could maximize the horizontal exposure area of the Si substrate and have little adverse effect on its light absorption. The design is supported by theory simulation and could lead to expectable PEC performance by precisely controlling the geometry and size of the AuNR which will trigger localized surface plasmon resonance (LSPR), bringing about a prominent enhancement of the light harvesting ability and exciting vast hot electrons under light illumination. Generated electrons could transfer across the Schottky junction formed by AuNR and TiO2 to contribute to the hydrogen evolution reaction (HER). The excellent hydrogen production performance with an onset potential of 0.32 V-RHE of our prepared HN electrode could be attributed to the synergetic effect of an electrochemical and PEC process, and the maximum photon-to-energy conversion efficiency reaches 13.3%. The experimental results are in good accordance with the simulation analysis and demonstrate an enhancement of the catalytic performance by optimizing the sizes of those components. This work may provide a new path to boost hydrogen production performance by designing customized HNs with a positive effect for electrocatalysis or photoelectrocatalysis.