Surface-coordination-induced selective synthesis of cubic and orthorhombic NaNbO3 and their photocatalytic properties

NaNbO3 photocatalysts with cubic and orthorhombic structures were selectively fabricated at a low temperature using different starting reagents through a surface coordination modulation. The samples were characterized by X-ray diffraction, field emission-transmission electron microscopy, ultraviolet-visible absorption spectroscopy and Fourier transform infrared spectroscopy. A surface ligand coordination effect is proposed to understand the crystal growth mechanism of cubic NaNbO3. Induced by the organic ligands, cubic NaNbO3 could be prepared at a temperature as low as 500 degrees C. Interestingly, the as-synthesized cubic NaNbO3 shows better photocatalytic performances than those prepared at temperatures over 600 degrees C by the conventional way, both in H-2 evolution from methanol aqueous solution and CO2 photoreduction in the gas phase. The enhanced photocatalytic activities could be attributed to the preferred crystal structure induced by the surface ligand coordination and the larger surface area obtained from the low formation temperature.