Effect of porosity on structural, optical, thermal, and electrical properties of nickel-foam coated graphene sheets

Nickel foam of various pore-size coated graphene thin film of 200 nm thickness was investigated as a function of the pore size. The structural properties were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The optical properties were analyzed through the UV–Visible reflectance and Photoluminescence spectra. Hall Effect and Electrochemical impedance spectroscopy techniques were used to study the electrical and dielectric properties. The thermal properties were measured through the photothermal deflection technique. By decreasing the pore size, the electrical conductivity was increased from 9.42 × 107 to 33.26 × 107 S m−1, volume and surface carrier densities were decreased from −8.66 × 1021 to −2.05 × 1021 cm−3 and from −1.13 × 1014 cm−2 to −0.41 × 1014 cm−2; respectively, the specific capacitance was increased from 15.52 × 106 F to 19.65 × 106 F and the dielectric permittivity of value in the order of 1.5 × 103 F m−1 was decreased with the frequency. It was developed the photothermal deflection technique and discussed its sensitivity to the determination of thermal properties which show that the thermal conductivity decreased from 4.12 to 3.58 W m−1 K−1 and the thermal diffusivity decreased from 0.146 to 0.109 cm2 s−1. It was established semi-empirical relationships which allow to deduce the thermal properties and optical band gap without needing to measure them. These results introduce the graphene coated on Nickel foam sheets as good candidate for potential use in photoelectric and thermoelectric devices.