Oxynitride from Oxide versus Nitride: Manifesting Competitive and Synergistic Properties in Titanium Oxynitride for Solar‐Driven Water Splitting and Nitrogen Fixation

The present study investigates the phase formation of the titanium oxynitride (TiO x N y ) system using the “oxide‐to‐oxynitride” and “nitride‐to‐oxynitride” synthesis strategies. The XRD patterns of both the materials show peaks corresponding to Ti–N and Ti–O lattices, confirming the formation of Ti–oxynitride system. Accordingly, the presence of Ti 3+ –N 3− and Ti 4+ –2O 2− signals is also confirmed by XPS analysis. The TiO x N y derived from oxide (TO‐TON) exhibits wide visible light absorption with a narrow‐bandgap energy of ≈2.30 eV, while the nitride‐derived–TiO x N y (TN‐TON) exhibits relatively a wide‐bandgap energy (≈2.92 eV) along with the plasmonic band of TiN. In line with this, an enhanced recombination resistance and charge carriers with extended lifetime are observed for TN‐TON (4.47 ns) and TO‐TON (4.33 ns) systems via photoluminescence and time‐resolved photoluminescence analysis. Consequently, the TN‐TON system demonstrates a superior H 2 /NH 3 production at a rate of ≈1432/646 μmol g −1 h −1 under solar irradiation, while it is ≈1136/553 μmol g −1 h −1 for the TO‐TON system. These efficiencies are ≈20× and 3× times higher than the bare TiN and TiO 2 , respectively, toward H 2 /NH 3 production. The insights from this study demonstrate that the nitride‐ and oxide‐based precursors likely manifest synergistic and competitive properties, respectively, in the resulting oxynitride system.