Shape-Controlled Synthesis of Cu 3 TeO 6 Nanoparticles with Photocatalytic Features.

Cu3 TeO6 (CTO) has been synthesized by hydrothermal synthesis applying different pH values without any template or a calcination step to control the crystalline phase and the morphology of nanoparticles. The physicochemical properties characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, N2 adsorption, X-ray photoelectron spectroscopy, and diffuse reflectance ultraviolet-visible (DRUV-vis) spectroscopy techniques revealed that the pH values significantly influence the crystal growth. In acidic media (pH = 2), crystal growth has not been achieved. At pH = 4, the yield is low (10%), and the CTO presents irregular morphology. At pH = 6, the yield increases (up to 71%) obtaining an agglomeration of nanoparticles into spherical morphology. At basic conditions (pH = 8), the yield increases up to 90% and the morphology is the same as the sample obtained at pH = 6. At high basic conditions (pH = 10), the yield is similar (92%), although the morphology changes totally to dispersed nanoparticles. Importantly, the as-prepared CTO semiconductor presents photocatalytic activity for H2 production using triethanolamine as a sacrificial agent under visible light illumination. The results also revealed that the nanoparticles agglomerated in a spherical morphology with larger surface area presented almost double activities in H2 production compared to heterogeneously sized particles. These results highlight the suitable optoelectronic properties, including optical band gap, energy levels, and photoconductivity of CTO semiconductors for their use in photocatalytic H2 production.