| Summary: | Recently, sophisticated technologies are applied to design a certain surface nature that can have superhydrophobic properties. Thus, a simple spray technique was introduced to prepare a superhydrophobic surface using rGO with Ni-S system (rGO-Ni) by using NiSO<sub>4</sub> catalyst under microwave irradiation at various reaction times of 5, 10, 20, and 30 min. The GO reduction was conducted at a fixed Ar/H<sub>2</sub> ratio, a flow rate of 0.4 L/min, microwave power of 720 W, and a mass of 0.5 g. GO powder with nickel sulfate catalyst was treated under Ar/H<sub>2</sub> (4:1) mixture for GO reduction, where Ar and H<sub>2</sub> were expected to prevent the rebinding of oxygen released from GO. The result of XRD and Raman measurement confirms that rGO-Ni prepared at reaction time 20 min exhibit the highest reduction of GO and the presence of various Ni-S crystal structures such as NiS, NiS<sub>2</sub>, Ni<sub>3</sub>S<sub>2</sub>, and Ni<sub>3</sub>S<sub>4</sub> due to decomposition of NiSO<sub>4</sub>. The rGO-Ni coating performance shows superhydrophobic nature with a contact angle of 150.1°. The AFM images show that the addition of nickel to rGO produces a quasi-periodic spike structure, which increases the superhydrophobicity of the r-GO-Ni coated glass with a contact angle of 152.6°. It is emphasized that the proposed simple spray coating using rGO-Ni provides a more favorable option for industry application in obtaining superhydrophobic surfaces.
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