Activated carbon fibers for toxic gas removal based on electrical investigation: Mechanistic study of p-type/n-type junction structures

Byong Chol Bai,Ji Sun Im,Young-Seak Lee

doi:10.1038/s41598-019-50707-x

Abstract

In this study, we evaluated the potential use of CuO-ZnO combination structures with activated carbon fibers (ACFs) for the adsorption (by ACFs) and electrochemical detection (by CuO-ZnO) by of SO2 gas. The gas adsorptivity was concluded to improve as a result of the synergetic effects of physical adsorption by the micropores and mesopores, the specific surface area developed by chemical activation and the chemical adsorption reaction between SO2 and the transition metals introduced in the CuO-ZnO combination structures. From comparison of the SO2 sensing properties, the CuO-ZnO combination structures with ACFs exhibited the fastest sensing capability. This result can be attributed to the larger specific surface area of the semiconductor, which extended its depletion layer by forming p-type CuO/n-type ZnO junctions. This phenomenon led to good SO2 detection through a decrease in the resistance; thus, the contributions of the sensing responses of p-type CuO and n-type ZnO represent a predominant characteristic of the sensor. These types of mechanisms were proven through various physicochemical and electrical characterization methods, especially through evaluation of the SO2 sensing capability of the CuO-ZnO combination structures with ACFs. The reversible sensing capability indicates that the p-n junction structure changed the electrical properties of the ACFs, leading to an intriguing sensing mechanism.

Highlights

Unlike soil and water pollution, air pollution is not a local problem limited to the country where the pollution source is located; rather, air pollution is an international issue because it spreads over a wide area, including adjacent countries, due to its characteristics[1]
In this paper, we focused on evaluating the potential use of the prepared activated carbon fibers (ACFs) for adsorption and electrochemical detection of SO2 gas
The dispersion and aggregation of CuO and ZnO strongly influenced the morphology of the ACFs

Summary

Introduction

Unlike soil and water pollution, air pollution is not a local problem limited to the country where the pollution source is located; rather, air pollution is an international issue because it spreads over a wide area, including adjacent countries, due to its characteristics[1]. In which two different metal oxides structures have recently become attractive candidates as sensing layers due to their potential to enhance gas sensitivity by a larger modulation in current through the p-n junction barrier than a single metal structure[15,16] These kinds of material should satisfy three main criteria when it needs combination each other. Over the last several decades, ACFs have attracted attention as a promising material that could satisfy the above criteria because ACFs have a high specific surface area for enhanced gas adsorption, excellent electrical properties for high sensitivity and chemical stability for resistance to acidic and high temperature conditions[17,18,19]. The chemical and textural properties of these carbon materials were evaluated for their potential application in the adsorption of harmful gas

Methods

Results

Conclusion