Controlled synthesis of cobalt telluride superstructures for the visible light photo-conversion of carbon dioxide into methane

• Cobalt telluride with varied morphology can be synthesized via one pot hydrothermal synthesis.
• The reaction time, use of surfactants and reaction temperature play a major role on morphology.
• Cobalt telluride nanostructures can be efficiently used as photocatalyst under visible light irradiation.
• CoTe can be used for photoreduction of CO2 into CH4.

The significant increase in the CO2 levels as a result of combustion of hydrocarbons fuels resulted in global warming. The use of solar base technology may decrease CO2 concentration but at the same time can be helpful in meeting energy demands. Moreover, most of the photocatalysts work in ultraviolet region of light. In the present work, a successful effort has been made to synthesize a photocatalyst which works in visible region of light. CoTe nanostructures with multiform architectures such as nanospheres, nanodisks, nanobelts, irregular nanoflakes and 3D layered nanostructures have been synthesized through a facile hydrothermal method. A series of well-ordered experiments demonstrated that shape and size of as-synthesized nanostructures can be adjusted effectively by directing reaction conditions such as alkalinity of reaction medium (concentration of KOH), reaction time and use of different surfactants. The X-ray diffraction (XRD) analysis confirmed the hexagonal phase of synthesized samples. UV–visible spectroscopic analysis was employed to evaluate the band gap value and to confirm the activity of nanostructures in visible region of electromagnetic radiations. Valence band position of synthesized CoTe nanostructures was determined by using X-ray photoelectron spectroscopy (XPS). The BET analysis has been employed to study the surface area of synthesized nanostructures. The photocatalytic activity has been studied for the photoreduction of carbon dioxide (CO2) into methane (CH4). The effects of different morphologies and particles size on the photocatalytic activity of synthesized nanostructures have been studied. The photocatalytic activity of present nanostructures is greater than most of single semiconductor photocatalysts reported earlier.

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