Experimental Investigation of SnO₂ an‎d ZnO Nanoparticles an‎d Their Composite for CO₂ Adsorption an‎d Chemiresistive Sensing Applications

3/14/2027 12:00:00 AM

In this study, tin oxide (SnO₂), zinc oxide (ZnO) nanoparticles, an‎d their composite structures were investigated for CO₂ adsorption an‎d sensing applications. Structural analyses using XRD, FTIR, an‎d SEM techniques confirmed that the nanocomposites possess an appropriate morphology an‎d a high specific surface area favorable for CO₂ adsorption. Specifically, the adsorption capacity of the SnO₂ (75%)/ZnO (25%) nanocomposite was 3.6 mmol/g at 1 bar an‎d 25 °C, representing a remarkable enhancement compared to pure ZnO (2.2 mmol/g) an‎d pure SnO₂ (2.7 mmol/g). To optimize the adsorption conditions, the response surface methodology (RSM) based on the central composite design (CCD) was employed. The results revealed that temperature, pressure, an‎d the SnO₂–ZnO composite formation significantly influence the adsorption capacity. Under the optimized conditions (25 °C, 9 bar, an‎d 75% SnO₂ / 25% ZnO composition), the adsorption capacity reached 7.741 mmol/g. The Langmuir isotherm model provided the best fit to the experimental data, indicating that CO₂ adsorption on the nanocomposite occurs via a physical adsorption mechanism. Although the kinetic analysis showed a better correlation with the pseudo-second-order model, the thermodynamic parameters confirmed that the process is physical, reversible, an‎d monolayer in nature. Thermodynamic eva‎luation further demonstrated that the adsorption process is exothermic an‎d spontaneous. In cyclic regeneration tests, the ZnO/SnO₂ nanocomposite retained about 90% of its initial adsorption capacity after five adsorption–desorption cycles, confirming its excellent stability an‎d reusability under various operating conditions. In the CO₂ gas-sensing section, sensors based on ZnO/SnO₂ (75% SnO₂ an‎d 25% ZnO) exhibited superior performance compared to pure SnO₂- an‎d ZnO-based sensors. This improvement arises from the synergistic interaction between the two oxides, where SnO₂ provides high surface adsorption capability, an‎d ZnO contributes to an increased number of active sites. The chemiresistive-type sensors based on SnO₂, ZnO, an‎d their nanocomposite (75:25 ratio) were eva‎luated for CO₂ detection. The synthesized nanocomposite sensor demonstrated the highest voltage response (ΔV), shortest response/recovery times, an‎d greatest voltage dro‎p percentage compared to the pristine materials. At 250 °C under batch conditions, the composite sensor exhibited a response of 1.4 V, with a response time of 20–30 s an‎d a recovery time of 25–35 s, indicating faster dynamic behavior than pure SnO₂ an‎d ZnO. This enhanced sensing performance is attributed to the formation of heterogeneous interfacial regions, the increased number of active sites, an‎d improved electrical conductivity. The optimized composition of 75% SnO₂ an‎d 25% ZnO effectively enhanced the sensitivity, speed, an‎d stability of the CO₂ sensor under operational conditions. Keywords: chemiresistive sensor, adsorption, CO₂, nanocomposite, zinc oxide, tin oxide, conductivity

حسگر مقاومتي , جذب , CO₂ , نانوكامپوزيت , نانواكسيد روي , نانواكسيد قلع , هدايت سنجي

chemiresistive sensor , adsorption , CO₂ , nanocomposite , zinc oxide , tin oxide , conductivity

Firouzeh Salimian

Dr.Alireza Hemmati