CO2 electrochemical sensor based on two-dimensional MoTe2 nanoplates: the effect of annealing, Mo and Te concentrations.

The two-dimensional materials are promising candidates for gas-sensing applications due to their unique properties as well as binary compounds. Here, the properties of MoO₃:TeO₂ thin films, and 2H-MoTe₂ gas sensing for CO₂ detection are reported. For this purpose, MoO₃:TeO₂ thin films are deposited with three different molar concentrations using the spray pyrolysis method. The structural properties, morphology, energy gap, as well as CO₂ gas sensing of MoO₃:TeO₂ thin films are studied before and after annealing at T = 773 K. The XRD results showed that after annealing at T = 773 K, an important two-dimensional phase of Hexagonal or 2H-MoTe₂ is formed in the molar concentration of MoO₃:TeO₂ (3:1). FE-SEM images showed that the thin films are agglutinate structures before annealing the morphology, but are nanoplates for MoO₃:TeO₂ (3:1). Also, after annealing at T = 773 K and gas leaving the surface of the thin film, the morphology of the thin films is polygonal. UV–Vis spectroscopy showed that the energy gap of the thin films varies in the range of 2.30–2.77 eV. The results of electrochemical CO₂ sensing showed that the sheet resistance (Rs) of all thin films before and after annealing at T = 773 K, under the CO₂ target gas, changes linearly, and the gradient of the curves increased after annealing. These changes are significant after annealing for the molar percentage of MoO₃:TeO₂ (3:1) due to the formation of the 2H-MoTe₂ two-dimensional phases. [ABSTRACT FROM AUTHOR]