Dual-Functional Schottky-Barrier-Free Plasmonic TiN/TiO₂ Photocatalyst for Efficient NH₃ and H₂ Production

Titanium nitride has garnered much attention owing to its high charge carrier density and low work function. These merits compensate for the shortcomings of traditional photocatalysts. Herein we report on the synthesis of TiN/TiO₂ nanoparticles (NPs) as a new Schottky-barrier-free plasmonic photocatalyst (SBFPP) through the oxidation of commercially available TiN NPs. Our SBFPP possesses abundant oxygen vacancies (OVs) and the ability to generate hot charge carriers. The TiN NPs oxidized at 400 °C for 2 h, which is designated as TiN-2, exhibit broad light absorption and a high OV concentration. Theoretical calculations have revealed that the presence of OVs and nitrogen dopants leads to the formation of defect electronic states in TiO₂. Hot electrons from TiN can efficiently migrate to these defect states, hindering the rapid electron-hole recombination. Besides the efficient photocatalytic nitrogen fixation, the TiN-2 NPs also exhibit excellent hydrogen generation performance. Furthermore, the photocatalytic film formed by combining the TiN/TiO₂ NPs and a porous poly(vinyl alcohol) film dramatically improves the photocatalytic nitrogen fixation performance, giving an enhancement of ∼4.4 times in comparison with the TiN-2 NPs. This study unveils a promising avenue for the rational design of plasmonic photocatalysts and facilitates the development of practical applications in the field of photocatalysis.