Oxidation behavior of TiC and TiCN and their potential photocatalytic activity in a semi-oxidized state.

The oxidation behavior of titanium carbide (TiC) and titanium carbonitride (TiCN) warrants significant attention. This study investigates the oxidation behavior of internally doped TiC and TiCN in ambient air by varying the oxidation temperature and explores their photocatalytic degradation activity. Macroscopic observations, combined with XRD and SEM analyses, reveal a pronounced color change during oxidation, with TiC exhibiting superior oxidation resistance compared to TiCN. TiC and TiCN were oxidized at 800 °C and 500 °C for 2 h, respectively, achieving substantial oxidation. During the oxidation process, TiC is directly oxidized to TiO, while in TiCN, C is first replaced by O, followed by N. The final oxidation product for both materials is rutile TiO. TG-DSC and TPO-IR analyses suggest that the C species in TiC is more complex than that in TiCN, attributed to the presence of C atoms with varying graphitization degrees embedded within the TiC lattice. In assessing photocatalytic degradation activity following semi-oxidization, TiC and TiCN exhibited optimal activity after oxidation for 2 h at approximately 400 °C and 500 °C, respectively, with residual rates of rhodamine B (RhB) at 3.85% and 9.37% after 240 min of degradation and adsorption. These results indicate that TiCN demonstrates superior adsorption and degradation capacities for RhB compared to oxidized TiC. Furthermore, UV-Vis DRS and XPS detection results confirm the formation of N and/or C inner-doped modified TiO in TiC and TiCN following appropriate semi-oxidization.