*2.1.1 In-Situ thermal decomposition*

At first, aqueous solution of zinc (II) nitrate hexahydrate and hydrazinium benzoate undergoes through in situ mixing, thereby yielding a precursor complex. However, molar concentration of these two chemicals is 0.01 mol and 0.02 mol respectively. Both of them should be stirred consistently. However, the final mixture exhibits concentrated product comprising an alleviation in its volume. Then, all constituents should be subjected to drying after cooling, and cleaning process. Now take 1 mg of graphene and disperse it into 5 ml of ethanol, allowing it for stirring of 1 h, similarly 10 mg complex precursor of zinc benzoate dihydrazinate is to add up and repeat sonication process. The decomposition of complex into nanoparticles of ZnO results in their coating on graphene sheets as the transfer of contents to a fine silica pot, undergoes an environment of 200°C temperature for 2 h.

### **2.2 Physical properties of graphene/semiconductor hybrids**

Graphene as well as Zinc oxide exhibits discrepancies up to some extent when considered separately. Therefore, the prime role of this combination mainly leads to the compensation of these flaws. This synergistic combination has been undergone comprehensive investigation, as it proves to be an excellent candidate of future devices, because of the enhancement in most of the properties like chemical stability, electrical etc. [19].

#### *2.2.1 Photocatalytic properties*

The interaction of graphene along with ZnO semiconductor, is ultimately vigorous. Therefore, it results in quickest movement of photo-generate negatively charged particles from Zinc oxide to graphene. Yet, another notable activity is the alleviation,

for recombination process of these electrons. In general, activity of the photocatalytic process rises, thereby imparting a constructive role in these properties [19].

#### *2.2.2 Electrical properties*

Another big advantage of graphene semiconductor hybrids is particularly its improvement of the electrode materials for supercapacitors. This renovation arises because of the various factors like specific surface area enhancement, outstanding cyclical stability, elevation in energy as well as power density, better ionic and electrical conduction performance. ZnO particles as well as graphene enclosed porous carbon have much improved conductivity of electrode entirely due to their combination. In addition, electron's movement from ZnO to the layer of graphene is the manifestation to the alleviation of defect emission. On the contrary, movement of charge from graphene to defect state of the given semiconductor causes an enhancement of defect levels contribution [19].
