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.
