Preparation and Characterization of rGO Electrode for Electrochemical Gas Sensor
Authors: Kim Hyo Jin , Kim Inho , Lee Kie-Won , Yoon Dae Ho , Han Sang-Do 
Published: May 2020

Introduction

Nowadays, an electrochemical gas sensor has attracted considerable attention because of its highly selective, sensitive stable and cost-effective characteristics. The conventional electrochemical gas sensor consists of reference, counter and sensing electrodes, and having a liquid electrolyte in a chamber. In general, gas sensor performances, i.e. sensitivity, selectivity, response time and life time depends on its structure and materials of electrolyte and electrode [1]. Carbon materials such as graphite, graphene, activated carbon and CNTs are widely used as an electrode material of electrochemical gas sensors [2]. The reduced graphene oxide (rGO) is one of the prominent material for electrode material, because of synthesized and mass-produced easily. The rGO is commonly synthesized by reducing graphene oxide (GO) by the Hummer’s method [3]. In this study, an electrochemical gas sensors were fabricated with activated carbon, graphite, and rGO with a noble metal catalyst as an electrode material. And the characteristics of the sensing performances for the hazardous gases were investigated.

Method

Graphite flakes were oxidized by modified Hummer’s method with additional KMnO4 [4]. The rGO was prepared according to the work by Park et al. [5] Chemical reduction of graphene oxide sheets was done with hydrazine monohydrate for 12 h at 80 °C with stirring. The agglomerated particles of resulting suspension were dispersed with a short sonication of less than 5 min. An electrode paste was prepared by mixing noble metals such as platinum, iridium and ruthenium with activated carbon, graphite and rGO. Then, the prepared paste was screen-printed on the flexible porous PTFE film The working electrode, counter electrode and reference electrode screen-printed on the PTFE (0.12mm of thickness) was prepared with Pt-carbon mixture material. Electrodes, filters and membranes were assembled in a polycarbonate case (10 x 10 x 3mm3) for gas sensing operation electrochemically.
Characterization of the materials was carried out through SEM-EDAX and XRD. The Raman spectra of the electrode materials were collected with radiation source a laser of 514.5 nm wavelength. In order to observe the oxidation-reduction reaction, cyclic voltammetric measurements were performed in an SP-300 potentiostat/galvanostat (Bio-Logic, France). Current change was measured using precision source/measure unit B2900A (Keysight Technologies). After that, the effect of carbon type on the current change by gas reaction was discussed.

Results and Conclusions

In conclusion, we have prepared a rGO and designed and fabricated an electrochemical gas sensor. We have investigated the gas sensing performance depends on carbon materials as an electrode, and systemically characterized by FESEM, XRD, Raman and cyclic voltammetry. The synthesized rGO with noble metal showed higher responses for hazardous gases than other carbon based electrode. Furthermore, ongoing studies are needed to noble metal effects for high sensitivity and selectivity. The proposed sensor could potentially provide extension of sensor applications with their high performances and small power consumption.

References

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