Enhancing humidity sensing performance: the effect of Nitrogen doped on Electrochemical Reduced Graphene Oxide (ERGO)

This work presents the effect of nitrogen (N₂) doped in aqueous solution of Graphene Oxide (GO) deposited onto the surface of the Aurum (Au) 200um spacing Interdigitated Electrode (IDE) via electrochemical deposition (ECD) method. Electrochemical deposition was the easiest and cost effective approach to synthesis of graphene oxide. It is an alternative green route to substitute the conventional Hummer's method which is commonly used hydrazine for GO reduction. However, this chemical is highly toxic to the environment and any living creatures. In the ECD process, two Au samples were used, one doped with nitrogen and other without nitrogen. The cyclic voltammetry window parameter was set up at sweep potential from -0.4V (start) to -0.4V (stop), vertex potential between the range -0.4V (upper) and -1.1 (lower), scan rate 0.005V/s and 10 cycles in the 40°C water bath temperature for each of the samples. The fabricated samples were characterized using electrochemical impedance spectroscopy (EIS) to investigate the electrochemical properties of ERGO. The FRA measurement was set up to 1MHz frequency at different applied potential ranges in between 0.2V, 0.4V and 0.6V for each of the fabricated samples. Subsequently, the humidity performance was observed on the different relative humidity (RH) in between 40%RH-90%RH at applied potential 0.2V. Finding shows that the addition of nitrogen into aqueous GO contributes to the remarkable increase in ionic conductivity as well as high sensitivity response towards humidity.

I. Introduction

The humidity sensor has been used widely in the determination of the moisture content. In some respects, humidity sensing plays a significant role in the industrial process. These roles can be implemented through a wide range of applications, such as agricultural, pharmaceutical production, food storage, weather forecasting, domestic machine controlling, electronics product and biomedical applications [1] . The measurement of humidity can be determined by converting the physical amount of water vapour in the environment into a measurable signal. There are numerous types of humidity sensors namely capacitive, resistive, impedance, quartz crystal microbalance, surface acoustic wave, optic-fiber and resonance [2 , 3] which is the selection of them depends on its specific application. Thus, the important factors that require to consider to obtain optimal humidity sensors includes the accuracy, response time, stability, repeatability, sensitivity and hysteresis. In addition, the quality of the sensor also affected by other parameters, such as the structure morphology as surface reaction, material as sensing media, and system preparation [4] .