Photoelectrochemical Methanol Oxidation on TiN Nanoparticles Supported on TiO2

Abstract

Titanium nitride (TiN) is a metallic nitride that has optical properties similar to gold, thus enabling it to support plasmonic resonances in visible region [1, 2]. It has been considered as an attractive alternative to noble plasmonic metals due to low cost, high mechanical and thermal stability and flexibility in terms of material design [2]. While the plasmon-driven photocatalytic reactions of gold nanoparticles have been demonstrated, very little work has been reported on photocatalytic properties of supported TiN nanoparticles. It has been shown recently [3] that cubic 50 nm TiN nanoparticles supported on TiO2 nanowires provide greater photocurrent enhancement for photoelectrochemical water splitting compared to spherical Au nanoparticles. Increased hot carrier generation by the TiN nanoparticles followed by more efficient carrier collection by TiO2 was cited as the cause. Here, plasmonic and catalytic properties of a TiN/TiO2 nanoparticle composite are probed in methanol oxidation reaction. The effects of variables such as plasmonic nanoparticle loading and particle size on the efficiency of visible to chemical energy conversion are investigated and discussed. TiO2-supported TiN photocatalysts were made from commercial 20 and 50 nm TiN (PlasmaChem), and TiO2 nanoparticles (Degussa) by wet chemistry methods. X-Ray Photoelectron Spectroscopy and high resolution transmission electron microscopy were used for the analysis of the catalysts’ surface composition and morphology, respectively. Electrochemical experiments were conducted in a three-electrode photoelectrochemical cell. The TiN/TiO2 films on FTO-coated glass served as the working electrodes (WEs), while platinum foil and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as counter and reference electrodes, respectively. LED lights (ThorLabs) were used as a light source.