Decoding Plasmonic Enhancement Pathways in Group 4 Metal Nitride‐TiO ₂ Composites: Rhodamine B Dye Degradation Case Study

ABSTRACT Traditional photocatalysis has predominantly focused on TiO 2 due its low cost, chemical stability, and non‐toxicity, however, its wide bandgap (>3 eV) limits solar absorption to under 5%. Plasmonic materials address this by extending light absorption into the visible and near‐infrared range, enhancing catalytic activity through localized electromagnetic fields, hot carriers, and photothermal effects. Plasmonic transition metal nitrides have emerged as promising, cost‐effective alternatives to noble metals due to their strong broadband absorption and chemical stability. While earlier studies attribute their photocatalytic enhancement mainly to hot carrier injection, a more detailed assessment is needed to properly understand the enhancement pathway. This study synthesizes composites of TiN, ZrN, and HfN with commercial P25 TiO 2 and evaluates their photocatalytic performance via Rhodamine B dye degradation. Under 100 mW cm −2 illumination, the 1 wt% ZrN/TiO 2 composite achieves over 99% dye degradation in 50 min, outperforming TiN and HfN, which require 10 wt% loading for similar results. By analyzing reaction temperature profiles and degradation kinetics under different light intensities, the study finds that hot carrier effects dominate in TiN/TiO 2 and ZrN/TiO 2 systems, while photothermal effects play a larger role in HfN/TiO 2 composites. This highlights the distinct mechanisms by which plasmonic nitrides enhance photocatalytic efficiency.