Roles of Vanadium and Nitrogen in Photocatalytic Activity of VN-Codoped TiO₂ Photocatalyst

In the present manuscript, we explore the VN-codoped TiO₂ system intended to understand the role played by each dopant in synergistic enhancement in performance of TiO₂ photocatalyst. The photocatalytic decomposition of organic pollutants in aqueous solution under visible light was used as a probe reaction to evaluate the performance of VN-codoped TiO₂ samples with different V and N concentrations. An optical measurement of VN-codoped TiO₂ shows considerable improved visible light absorption with increase in V-concentration as compared to increase in N concentration, which was due to the effective narrowing of the band gap by V-doping. The energy levels formed by N-dopants act as the trapping centers for photogenerated holes to suppress recombination process as indicated by PL and TRPL results. It is also observed that at high V-concentrations recombination centers are created in the form of oxygen vacancies as indicated by XPS and PL. In VN-codoped TiO₂ , addition of N partially fills these oxygen vacancies to reduce the number of recombination centers and prolong the lifetime of charge carriers. Thus, V improves the visible light absorption while N reduces the recombination of electron-hole pairs, thus creating the synergistic effect to produce three times better performance than pure TiO₂ .