{111} faceted Li4Ti5O12 octahedra as the reference electrode material in a nanostructured potentiometric CO2 sensor

A viable methodology for the synthesis of lithium titanate (Li4Ti5O12) octahedra via a one pot hydrothermal route in an aqueous medium using CTAB has been demonstrated. The synthesized Li4Ti5O12 octahedral nanoparticles were observed to be highly crystalline with a side edge length ranging from 30 to 120 nm. A plausible formation mechanism is put forth based on the findings obtained from the physicochemical characteristics supported by electron micrographs as a result of varying key parameters such as CTAB concentration, hydrothermal reaction time, and temperature. Furthermore, a critical evaluation of a potentiometric CO2 sensor with {111} faceted Li4Ti5O12 octahedral phase employed as the reference electrode, along with other nanoarchitectures, namely, 2D Li2CO3 flakes, 1D BaCO3 rods, and 3D TiO2 spheres, showed agreeable 'n' (number of cell reaction electrons) and EMF (electromotive force) values. EMF was found to be linear with the logarithm of CO2 partial pressure in the test range of 100-10 000 ppm. The sensor not only showed fair Nernstian behavior but was also found to be stable in both dry and humid environments at 500 degrees C. When compared to a potentiometric CO2 sensor fabricated using commercially available powders, a marked improvement in the sensor response was shown by the nanostructured sensor with a nearly six and three-fold enhancement in response and recovery time, respectively. The improved performance of the nanostructured potentiometric CO2 sensor was attributed to the high crystallinity and tailored morphologies of the nanomaterials employed as the sensing and reference electrodes.