Screen-Printed Carbon Electrode with Self-Assembled Aunps@Mxene for High Sensitive Electrochemical Gas Detection

Abstract

Introduction Gas sensors have been received extensive attentions due to the critical roles of various gases in industry, environmental monitoring and agriculture. A variety of gas sensing approaches has been developed such as gas chromatography, optical sensing, metal oxide semiconductor-based sensing and electrochemical sensing. Compared to other methods, electrochemical method features high sensitivity, low detection limit, good reproducibility and wide detection range, which has been explored for applications in real world. As a typical electrochemical device, screen printed electrodes (SPEs) can be easily and massively fabricated with good integration and low cost. Also, the easily tunable ink composition is another intriguing feature for specific applications. However, screen printed carbon electrodes (SPCEs) have inferior electrochemical catalysis to noble metal-based sensors despite of its low cost. To further improve the electrochemical performance of SPCEs for gas sensing, nanomaterials are considered as a promising alternative due to its high catalysis, fast electron transfer and large active surface area. MXene is a new class of two-dimensional materials such as Ti3C2X, in which X indicates oxygen- and fluorine-containing functional groups. MXene demonstrates outstanding electrochemical features with excellent catalytic ability. However, MXene materials can easily induce spontaneous oxidation reaction with oxygen and water due to its inherent feature. Therefore, nanocomposites with MXene and metal nanostructures are introduced to improve the stability and further enhance the catalytic performance. In this paper, a screen-printed carbon electrode (SPCE) with self-assembled AuNPs@MXene modification was developed for high sensitive electrochemical gas detection. The sensor performance was compared and evaluated with different concentrations of oxygen using cyclic voltammetry and chronoamperometry. Experimental Compressed air (21% O2) and nitrogen were used as the target gas and balancing gas, respectively. Room temperature ionic liquids 1-butyl-1-methylpyrrolidinium bis-(trifluoromethylsulfonyl)-imide ([C4mpy][NTf2], Aladdin, China) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6], Acros Organics, USA) were used as the supporting electrolyte by drop-casting on the sensor surface. Ti3C2X powders were synthesized by using HF to etch Ti3AlC2 particles as reported in the literature [1]. Gold nanoparticles were synthesized by using trisodium citrate and chloroauric acid as reported in the literature [2]. All chemicals were used as received without further purification. Screen-printed carbon electrodes were purchased from Zensor R&D Inc. A gas blender (MCQ100, Italy) was used for gas mixing, and the total gas flow rate was set constant as 200 standard cubic centimeter per minute (SCCM).An electrochemical analyzer CHI 1030 was used for electrochemical tests using cyclic voltammetry (CV) and constant potential chronoamperometry. Results The bare SPCE was first tested in 21% O2 and nitrogen using cyclic voltammetry, and a pair of reduction peak and oxidation peak can be apparently observed, validating the catalytic ability of carbon-based sensors for gas sensing. Two different RTILs were tested using as the electrolyte, and the results indicate that the sensor using [C4mpy][NTf2] presents higher current response and sensitivity. The sensing performance of bare SPCE, MXene modified SPCE and AuNPs@MXene modified SPCE was compared using CV and chronoamperometry, and AuNPs@MXene modified SPCE exhibits the highest current response and sensitivity due to the synergetic catalytic effect of MXene and AuNPs. The AuNPs@MXene modified SPCE was tested with different oxygen concentration, validating that the sensor has very high sensitivity, wide linear range, low detection limit and good reproducibility. Thus, the sensor can be a promising device for practical gas sensing applications in the real world.