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. 2023 Jan 29;15(3):685.
doi: 10.3390/polym15030685.

Valorization of Agricultural Waste as a Chemiresistor H2S-Gas Sensor: A Composite of Biodegradable-Electroactive Polyurethane-Urea and Activated-Carbon Composite Derived from Coconut-Shell Waste

Aamna Bibi  1 , Karen S Santiago  2 , Jui-Ming Yeh  1 , Hsui-Hui Chen  3
Affiliations

Valorization of Agricultural Waste as a Chemiresistor H2S-Gas Sensor: A Composite of Biodegradable-Electroactive Polyurethane-Urea and Activated-Carbon Composite Derived from Coconut-Shell Waste

Aamna Bibi et al. Polymers (Basel). .

Erratum in

Abstract

In this study, a high-performance H2S sensor that operates at RT was successfully fabricated using biodegradable electroactive polymer-polyurethane-urea (PUU) and PUU-activated-carbon (AC) composites as sensitive material. The PUU was synthesized through the copolymerization of biodegradable polycaprolactone diol and an electroactive amine-capped aniline trimer. AC, with a large surface area of 1620 m2/g and a pore diameter of 2 nm, was derived from coconut-shell waste. The composites, labeled PUU-AC1 and PUU-AC3, were prepared using a physical mixing method. The H2S-gas-sensing performance of PUU-AC0, PUU-AC1, and PUU-AC3 was evaluated. It was found that the PUU sensor demonstrated good H2S-sensing performance, with a sensitivity of 0.1269 ppm-1 H2S. The H2S-gas-sensing results indicated that the PUU-AC composites showed a higher response, compared with PUU-AC0. The enhanced H2S-response of the PUU-AC composites was speculated to be due to the high surface-area and abounding reaction-sites, which accelerated gas diffusion and adsorption and electron transfer. When detecting trace levels of H2S gas at 20 ppm, the sensitivity of the sensors based on PUU-AC1 and PUU-AC3 increased significantly. An observed 1.66 and 2.42 times' enhancement, respectively, in the sensors' sensitivity was evident, compared with PUU-AC0 alone. Moreover, the as-prepared sensors exhibited significantly high selectivity toward H2S, with minimal to almost negligible responses toward other gases, such as SO2, NO2, NH3, CO, and CO2.

Keywords: H2S gas sensor; PUU; activated carbon; biodegradable-electroactive; composite; room temperature.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Scheme for the preparation of polyurethane-urea (PUU-AC0).
Figure 1
Figure 1
Schematic diagram of the formation of AC (top) and preparation of ITO sensor (bottom) for measuring gas-sensing properties of PUU-AC0, PUU-AC1 and PUU-AC3.
Figure 2
Figure 2
Schematic representation of the gas-sensor measurement setup.
Figure 3
Figure 3
(a) N2 adsorption−desorption isotherms and the corresponding pore-size distribution (inset) and (b) Raman spectrum of AC.
Figure 4
Figure 4
(a) The FTIR spectra of PCL-diol, PMDI, ACAT and PUU (b) The representative FTIR spectra of AC, PUU-AC0 and PUU-AC composites.
Figure 5
Figure 5
SEM images of AC (a), PUU-AC0 (b), PUU-AC1 (c) and PUU-AC3 (d).
Figure 6
Figure 6
(a) Degradation profile of PUU-AC0 film in PBS (ph = 7.4) at 37 °C (b) Cyclic voltammogram of blank ITO, PUU-AC0, PUU-AC1 and PUU-AC3 (c) Current-Voltage curves of PUU-ACO, PUU-AC1, PUU-AC3 sensors between −1 V and +1 V.
Figure 7
Figure 7
(a) Current-time transient responses of sensor PUU-AC0, PUU-AC1 and PUU-AC3 to different concentrations of H2S in a range of 50-1 ppm. (b) Response curves of PUU-AC0, PUU-AC1 and PUU-AC3 sensor to increasing concentrations of H2S in 60% RH (V = +1 V). (c) The sensor sensitivity values were reported in the bar plot with water contact-angle pictures of samples captured by microscope (inset).
Figure 8
Figure 8
Dynamic-response–recovery-time curves of ITO sensors, based on PUU-AC0, PUU-AC1 and PUU-AC3 when exposed to 20 ppm of H2S gas at room temperature.
Figure 9
Figure 9
(a) Detection selectivity upon exposure to various vapors (20 ppm) operating at room temperature (b) The effect of relative humidity on sensor response and (c) stability of PUU-AC0, PUU-AC1 and PUU-AC3 sensors.
Figure 9
Figure 9
(a) Detection selectivity upon exposure to various vapors (20 ppm) operating at room temperature (b) The effect of relative humidity on sensor response and (c) stability of PUU-AC0, PUU-AC1 and PUU-AC3 sensors.
Figure 10
Figure 10
Five consecutive responses of PUU-AC0, PUU-AC1 and PUU-AC3 reported as normalized resistance (Ra-Rg) to the same concentration of H2S (20 ppm), flowed throughout the measuring chamber (1000 sccm) in 60% RH (V = +1 V).
Figure 11
Figure 11
Schematic diagram for H2S-gas sensing mechanism by ACAT-based polymer (PUU-AC0) and its composites (PUU-AC1, PUU-AC3).
See this image and copyright information in PMC

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