The adsorption properties of Cu, Ag, Zn, and Cd-modified SnP₃ monolayers for H₂S have been studied using density functional theory (DFT). Based on phonon spectrum calculations, a structurally stable intrinsic SnP₃ monolayer was obtained, based on which four metal-modified SnP₃ monolayers were constructed, and the band gaps of the modified SnP₃ monolayers were significantly reduced. The adsorption capacity of Cu, Zn-modified SnP₃ was better than that of Ag, Cd-modified SnP₃. The adsorption energies of Cu-modified SnP₃ and Zn-modified SnP₃ for H₂S were −0.749 eV and −0.639 eV, respectively. In addition, Cu-modified SnP₃ exhibited chemisorption for H₂S, while Zn-modified SnP₃ exhibited strong physisorption, indicating that it can be used as a sensor substrate. Co-adsorption studies showed that ambient gases such as N₂, O₂, and H₂O had little effect on H₂S. The band gap change rate of Zn-modified SnP₃ after adsorption of H₂S was as high as −28.52%. Recovery time studies based on Zn-modified SnP₃ showed that the desorption time of H₂S was 0.064 s at 298 K. Therefore, Zn-modified SnP₃ can be used as a promising sensor substrate for H₂S due to its good selectivity, sensitivity, and fast recovery time.

In this paper, tin oxidation (SnO _x )/tin-sulfide (SnS) heterostructures are synthesized by the post-oxidation of liquid-phase exfoliated SnS nanosheets in air. We comparatively analyzed the NO₂ gas response of samples with different oxidation levels to study the gas sensing mechanisms. The results show that the samples oxidized at 325 °C are the most sensitive to NO₂ gas molecules, followed by the samples oxidated at 350 °C, 400 °C and 450 °C. The repeatabilities of 350 °C samples are better than that of 325 °C, and there is almost no shift in the baseline. Thus this work systematically analyzed the gas sensing performance of SnO _x /SnS-based sensor oxidized at 350 °C. It exhibits a high response of 171% towards 1 ppb NO₂, a wide detecting range (from 1 ppb to 1 ppm), and an ultra-low theoretical detection limit of 5 ppt, and excellent repeatability at room temperature. The sensor also shows superior gas selectivity to NO₂ in comparison to several other gas molecules, such as NO, H₂, SO₂, CO, NH₃, and H₂O. After x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscope, and electron paramagnetic resonance characterizations combining first principle analysis, it is found that the outstanding NO₂ sensing behavior may be attributed to three factors: the Schottky contact between electrodes and SnO _x /SnS; active charge transfer in the surface and the interface layer of SnO _x /SnS heterostructures; and numerous oxygen vacancies generated during the post-oxidation process, which provides more adsorption sites and superior bandgap modulation. Such a heterostructure-based room-temperature sensor can be fabricated in miniaturized size with low cost, making it possible for large-scale applications.

Hybrid supercapacitors have attracted considerable attention for the use in the energy storage systems due to the simultaneous possession of high power and energy. Herein, Co ₃ O ₄ array with amorphous carbon on Ni foam has been derived from the Co-MOF. The electrochemical dynamics and energy storage mechanism of the prepared electrode have been investigated, which reveals the enhancement of the capacitive behavior with the scan rate. The electrochemically active specific surface area (ECSA) of our sample is calculated as 1416 cm ² for per square centimeter of electrode. The prepared material exhibits an excellent electrochemical performance (3.17 F · cm ⁻² at 1 mA · cm ⁻² and 2.076 F · cm ⁻² at 30 mA · cm ⁻² ). Further, the long-term life shows 96.7% capacity retention at 50 mV · s ⁻¹ after 20 000 cycles in KOH aqueous electrolyte. The Coulomb efficiency is noted to range from 95% to 100% even after 20 000 cycles. Further, the symmetrical solid-state supercapacitor represents a wide operating voltage range and high scan rate for practical applications. Three charged solid-state supercapacitors are observed to lit 160 parallel green LEDs (20 mA, 2.2V) for approximately 50 s. These findings from this study confirm the potential of Co ₃ O ₄ array with carbon hybridization as an effective supercapacitor electrode material.