Work

Temperature-dependent selectivity of p-n Cr₂O₃/ SnO₂ heterostructures towards the detection of m-xylene and CO2 gases

Year: 2025

Type: article

Abstract: The current study focuses on the fabrication of n-p SnO₂/Cr₂O₃ and p-n Cr₂O₃/SnO₂ heterostructures for the detection of m - x ylene and CO 2 utilizing the hydrothermal synthesis method, followed by calcination at 450 °C for 3 h. The structural studies confirmed the formation of n-p and p-n heterostructures of SnO₂/Cr₂O₃ and Cr₂O₃/SnO₂ nanostructured materials. Surface analyses showed spherical nanoparticles with minimal agglomerations, while Brunauer-Emmett-Teller analyses confirmed mesoporous nanomaterials with a large surface area of 105.4 m 2 /g for the Cr₂O₃/SnO₂. The optical analysis indicated a shift towards higher wavelengths, corresponding with an energy band gap reduction, which can be explained by lattice distortion and surface defects. The Cr₂O₃/SnO₂ nanospheres exhibited temperature-dependent selectivity towards m - x ylene at 200 °C and CO 2 at 150 °C. At a low temperature of 150 °C, the sensor demonstrated the highest response of 4.35 towards 1200 ppm CO 2 and a low detection limit (LoD) of 56.1 ppm and fast recovery/response times of 68/98 s. At 200 °C, the sensor displayed a best response of 5.59 towards 100 ppm m - x ylene, and a LoD of 0.0128 ppm and rapid rec/res times of 61/103 s. The sensor displayed a superior stability when tested over two consecutive cycles of CO 2 and xylene, and in 10, 20, and 30 % relative humidity. The sensor performance can be explained by the large surface area, surface defects, and high pore volume, allowing better gas adsorption, as well as the increased number of charge carriers due to the formation of a hole-accumulation layer deriving from the p-n junction in the heterostructure. The CO 2 and xylene sensing mechanisms were also discussed. • n-p SnO₂/Cr₂O₃ and p-n Cr₂O₃/SnO₂ heterostructures were fabricated using the hydrothermal method. • Cr 2 O 3 /SnO 2 heterostructure displayed a large surface area of 105.4 m 2 /g. • Cr₂O₃/SnO₂ exhibited temperature-dependent selectivity towards CO 2 at 150 °C and m - x ylene at 200 °C. • The sensor displayed a superior stability towards two consecutive cycles of CO 2 and xylene.

Source: Microchemical Journal

DOI: 10.1016/j.microc.2025.115464

Authors: Kholofelo M. Seloane, Rethabile Makole, Shaun Cronje, Hendrik C. Swart, David E. Motaung

Institutions: University of the Free State, Central University of Technology

Language: English

Topic: Gas Sensing Nanomaterials and Sensors

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,000

Funders: Department of Science and Innovation, South Africa, Department of Science and Technology, Ministry of Science and Technology, India