Photoelectrochemical Methanol Oxidation Under Visible and UV Excitation of TiO2-Supported TiN and ZrN Plasmonic Nanoparticles

Abstract

TiN and ZrN refractory transition metal nitride nanoparticles (NPs) have recently emerged as an alternative to noble metals in plasmonic applications. However, plasmon-driven photocatalysis by ZrN NPs is largely unexplored. In this study, optical properties, morphology, crystal structure and surface composition of in-house synthesized and commercial ZrN nanoparticles (NPs) are vigorously characterized in order to select the best candidate material for evaluation of activity towards CH3OH photoelectrochemical oxidation. The photocatalytic activity of TiO2-supported ZrN NPs is compared to that of TiN/TiO2 as a function of NP loading and illumination wavelength. Our results indicate that optical properties and photocatalytic activity of ZrN/TiO2 are strongly affected by ZrN surface oxidation and agglomeration. We found that under visible illumination, both in-house synthesized 17 nm ZrN and commercial 30 nm TiN NPs promote TiO2 activity for CH3OH oxidation, while under visible + UV excitation, an inhibition effect is observed. The differences between the TiN/TiO2 and ZrN/TiO2 interfaces are discussed and the mechanisms of promotion/inhibition of TiO2 photocatalytic activity by ZrN and TiN NPs are proposed. Electromagnetic simulations are used to facilitate interpretation of experimental extinctions and photocatalytic activities.