Plasmon Enhanced Photocatalysis with Group IV Metal Nitride and TiO2 Composites: Rhodamine B Dye Degradation Case Study

Traditional photocatalysis often employs TiO2 for its affordability and safety, but its large bandgap (>3 eV) limits solar absorption to under 5%. Plasmonic materials serve as sensitizers to expand absorption into the visible and near-IR spectrum while generating localized electromagnetic fields, hot carriers, and heat to boost catalytic efficiency. While noble metals have been extensively studied for visible light absorption, their high cost and poor oxidative stability have spurred interest in alternative plasmonic materials. Transition metal nitrides, such as TiN, ZrN, and HfN, offer strong absorption in the visible and near-IR regions and are cost-effective. In this study, TiN, ZrN, and HfN were combined with traditional P25 TiO2 to yield composite materials and their photocatalytic activity was evaluated by monitoring rhodamine B dye degradation. Under optimized conditions and 100 mW cm-2 illumination, degradation efficiencies of 96, 71, and 99% were observed for TiN/TiO2, ZrN/TiO2, and HfN/TiO2, respectively. Reaction temperature and power density studies allude to reaction efficiency enhancement due to a hot carrier driven process in TiN/TiO2 and ZrN/TiO2 systems. In the case of HfN/TiO2, photothermal contributions are likely to be significant.