Plasmonic enhancement of hydrogen production by water splitting with CdS nanowires protected by metallic TiN overlayers as highly efficient photocatalysts

Abstract

A novel CdS/TiN core-shell structure has been synthesized to produce the hydrogen gas in the photocatalytic water splitting (PWS) with sacrificial agents under simulated solar light (AM 1.5G). The single-crystalline and high-aspect-ratio CdS nanowires (NWs) are coated with different thicknesses of TiN layer. In particular, the CdS NWs with a thickness of 15-nm TiN showed the best performance in hydrogen production that can improve the hydrogen production rate by about 362% compared to the CdS NWs. In the meantime, it can avoid the detrimental issues regarding the use of CdS alone such as low stability and release of toxic component. This significant improvement of the TiN outer layer is a synergetic effect of three main factors, including the improvement of light absorption and electron concentration caused by surface plasmon resonance (SPR) enhancement effect, the reduction of the possibility of photo-induced carrier recombination, and the outstanding chemical stability during photocatalytic water splitting. In addition, the effects of protective TiN layer on the electric fields generated by light irradiance on the system have been calculated and simulated with the finite-difference time-domain (FDTD) method. The results are consistent with the proposed mechanism for best performance with plasmonic enhancement. The work represents a significant advance in the production of hydrogen via photocatalytic water splitting.