Carbon nanofiber–based CuSn(OН) ₆ and CuSnO ₃ composites for NO ₂ gas sensors and supercapacitors

Copper hydroxystannate, CuSn(OH)6, was obtained via a hydrothermal method from a mixture of solutions of copper(II) chloride and sodium stannate with the addition of sodium hydroxide solution until pH 10. The phase compositions of the hydrothermal synthesis and the thermal decomposition products were studied using thermal analysis, X-ray diffraction, scanning electron microscopy, and FTIR spectroscopy. It was established that at a synthesis temperature of 180 °C, a single-phase perovskite-like copper hydroxystannate is formed, with particles having cubic shapes measuring 35–38 nm (according to Scherrer’s equation). It was shown that the reaction of the CuSnO3/modified CNFs composite with NO2 at room temperature results in a 32% response at 2 ppm, whereas the response of the CuSn(OH)6/modified CNFs composite under the same conditions is 19%. The CuSnO3/modified CNF composite exhibits the best electrochemical characteristics compared to the CuSn(OH)6/modified CNF composite for use in supercapacitors. The composite material CuSnO3/modified CNFs demonstrated its applicability as an electrode material in supercapacitors, showing a specific capacitance of 288 F/g at a scan rate of 2 mV/s, compared to the CuSn(OH)6/modified CNFs (135 F/g). It was established that the specific capacitance of composites based on CNFs significantly exceeds that of single-phase copper stannates (14 and 6 F/g, respectively).