Preparation, characterization and photocatalytic activity of metal-loaded NaNbO3

Fe-, Ni-, Co- and Ag- loaded NaNbO3 catalysts were prepared and their activities have been investigated in the reaction of photocatalytic hydrogen generation. Me/NaNbO3 were synthesized by impregnation of NaNbO3 in an aqueous solution of metal nitrates and then by calcination at the temperature of 400 °C. The crystallographic phases and optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV–vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-Ray spectrometer (EDX) as its mode. The detailed analysis has revealed that all the investigated catalysts exhibit high crystallinity and the presence of Fe2O3, NiO, Co3O4 and Ag2O oxides on Me/NaNbO3 was confirmed. Finally, the influence of different metal loadings (Fe, Ni, Co and Ag) on the photocatalytic activity of NaNbO3 for photocatalytic hydrogen generation has been investigated. Here we report that among all the Me/NaNbO3 photocatalysts Ag-loaded NaNbO3 exhibited higher photocatalytic efficiency for photocatalytic hydrogen generation than NaNbO3.

Research Highlights
► The efficiencies of Fe, Ni, Co and Ag-loaded NaNbO3 in the reaction of photocatalytic hydrogen generation were investigated.
► The detailed analysis (XRD, HR-TEM, Raman and DR-UV-vis) indicated that Fe2O3, NiO, Co3O4 and Ag2O oxides existed on the surface of Me/NaNbO3 catalyst, respectively.
► Only Ag-loaded NaNbO3 exhibited higher photocatalytic efficiency than NaNbO3.
► Ag possess the highest electronegativity, and the difference between electronegativity of Ag (1.93) and Nb (1.60) is also the highest.
► This can be the reason of the highest hydrogen production activity of Ag/NaNbO3.