Electrosynthesis and microstructural characterization of amorphous zinc sulfide coatings as an alternative material for oxygen adsorption.

Abstract

Zinc sulfide materials are significantly employed in the development of photocatalytic and energy materials, as well as in environmental science. This paper presents the electrosynthesis of amorphous zinc sulfide coatings on zinc sheets at room temperature to develop a simple method to conventional processes. The system was assessed using thermodynamics and electrochemical tests (linear voltammetry and chronoamperometry) in the presence of sodium sulfide as sulfurizing agent varying the pH from 2 to 6, applied anodic potential (0.25 – 1.5 V vs Ag/AgCl) and processing time. The results revealed that amorphous zinc sulfide coatings can be formed on zinc sheets at pH higher than 2, while zinc sulfide coverage is maximized at processing times of 10 min. The thermodynamic analysis demonstrated that zinc sulfide is stable in a pH window from 1 to 12. Voltammetric tests showed a significant improvement of the kinetics of zinc sulfide generation when the applied potential is increased from 0.25 to 1.5 V vs Ag/AgCl achieving anodic currents of 0.043 A. Chronoamperometric tests carried out at different controlled anodic potentials and processing time followed by SEM/EDS characterization of the resulting coatings, revealed that amorphous zinc sulfide is formed while the oxygen adsorption is increased on the vacancies of zinc sulfide modifying the solid morphology when the anodic potential is modified from 0.25 to 1.5 V vs Ag/AgCl. The results are in good agreement with the thermodynamic modelling, representing an interesting opportunity towards the development of alternative materials for oxygen adsorption.

Keywords: zinc sulfide; electrosynthesis; oxygen