SYNTHESIS AND CHARACTERIZATION OF NICKELTUNGESTEN/ REDUCED GRAPHENE OXIDE NANOCOMPOSITE BASED AMMONIA SENSOR

Abstract

Nickel-tungsten/reduced grapheme oxide (NiW/RGO) nanocomposite was prepared by using chemical reduction method for electrochemical detection of ammonia. Ni/RGO and Ni-W different ratio/RGO nanocmposite were also synthesized using the same method to compare their performance for sensing ammonia in aqueous solution. The synthesized materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR and ultraviolet-visible spectroscopy (Uv-vis). Electrochemical properties of glassy carbon electrode modified using these nanomaterials were studied by employing cyclic voltammetry (CV) and Chronoamperometry methods. It was observed that Ni-W (1:1)/RGO/GCE sensor exhibited a superior electro oxidation surface towards ammonia oxidation in alkaline medium as evidenced from its highest peak current compared to the other modified electrodes. This is probably because of NiW/RGO nanocomposites high electro catalytic surface area (0.08512cm2) and the synergetic effect coming from Ni, W and RGO. Besides, NiW/RGO may be tolerance to the poisoning effect from intermediates accumulated on the surface of the electrode during the redox reaction. The effect of PH on ammonia oxidation on surface of NiW/RGO was also investigated using CV. It was noticed that the peak current increased with pH while peak potential slightly shifted toward a more positive value. NiW(1:1)/RGO/GCE sensor was applied for the detection of ammonia in standard solution under optimized experimental conditions. The sensor exhibited sensitivity -112mv/d and Lower detection limit 5.65 × 10-4 ppm in alkaline solution. Furthermore, the sensor shows good reproducibility with % RSD 3.5% and good stability. Therefore, NiW (1:1)/RGO nanocomposite sensor can be a potential candidate for the detection of ammonia based its electro oxidation in alkaline media.