Gas sensing properties of powder prepared from waste thermoelectric devices by wet reduction process

Abstract

In this study, n-type Bi2Te3 in thermoelectric scrap is recovered through a wet reduction process. The recovered powder (tellurium) is grafted onto gas sensor in a new application that is not a thermoelectric device. Bismuth-rich powder is prepared by adding hydrazine when pH of the solution is brought to 13 using NaOH. The pH of the filtered solution was reduced using HNO3, and then hydrazine was added to perform the re-reduction reaction. The tellurium-rich powder can be obtained through this reaction. The elemental analysis for these powders is confirmed by energy dispersive X-ray spectroscopy (EDS) analysis; the successful separation of bismuth and tellurium is confirmed. Separated tellurium powder is mixed with DMF solvent and ethyl cellulose binder to confirm gas sensing properties. The tellurium paste was exposed in NOx atmosphere and exhibited a rapid reaction rate and recovery rate of less than 3 minutes for the gas.