Role of reactive species in the photocatalytic degradation of amaranth by highly active N-doped $$\mathbf{WO}_{\mathbf{3}}$$ WO 3

Abstract

A novel, highly visible light active N-doped $$\hbox {WO}_{3}$$ ( $$\hbox {N}$$ - $$\hbox {WO}_{3})$$ is successfully synthesized via thermal decomposition of peroxotungstic acid–urea complex. The photocatalytic activity of $$\hbox {N}$$ - $$\hbox {WO}_{3}$$ is evaluated for the degradation of amaranth (AM) dye under visible and UVA light along with the role of reactive species, which has not yet been studied for $$\hbox {N}$$ - $$\hbox {WO}_{3}$$ photocatalysts. Doping of N into substitutional and interstitial sites of $$\hbox {WO}_{3}$$ is confirmed by X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy. At a pH of 7, 1 g $$\hbox {l}^{-1}$$ of $$\hbox {N}$$ - $$\hbox {WO}_{3}$$ can completely degrade $$10\,\hbox {mg } \hbox {l}^{-1}$$ of AM within 1 h under visible and UVA light. For the degradation of AM by $$\hbox {N}$$ - $$\hbox {WO}_{3}$$ under visible and UVA light, $$\hbox {h}^{+}$$ is found to be the main reactive species, while $$\cdot \hbox {OH}$$ contributes to a lesser extent. On the contrary, $$^{1}\hbox {O}_{2}, \cdot \hbox {O}_{2}^{-}$$ and $$\hbox {e}^{-}$$ show negligible roles. The crucial role of $$\hbox {h}^{+}$$ indicates effective suppression of electron–hole recombination after N doping. Dye sensitization and oxidation by reactive species are found to be the major pathway for the degradation of AM under visible and UVA light, respectively.