Surface functionalization of Co₃O₄ nanostructures

Surface functionalization is one of the handy methods to enhance the functional properties of metal oxide nanostructures. Accordingly, noble metal functionalization is widely employed in metal oxide gas sensors to improve the sensitivity, selectivity, stability, and response time/recovery time. Reporting work discusses the preparation of Pt-functionalized Co₃O₄ nanowalls for acetone sensing. The Co₃O₄ nanowalls were grown by thermal oxidation of metallic Co films at a temperature of 280 °C in normal atmospheric conditions. Besides, DC-magnetron sputtering was used to functionalize the Co₃O₄ nanowalls. The morphological, structural, and compositional analysis of the prepared material was carried out by using FE-SEM, CTEM, HRTEM, SAED, RAMAN, EPR, and EDX. The prepared material showed nanowalls around the nanopetals. The material follows the FCC structure of Co₃O₄; the most intense diffraction spots correspond to (311) and (400) crystallographic planes. The RAMAN spectra show five characteristic peaks at 195, 482, 521, 620, and 692 cm^-1 which belong to the symmetric phonon modes F_2g¹, E_g, F_2g², F₂g³ and A_g¹ of the crystalline Co₃O₄. The fabricated sensors showed a good response to acetone when operating at the temperature of 500 °C. Furthermore, Pt functionalized Co₃O₄ sensors demonstrated a ten times higher response compared to pristine material with a detection limit of 0.07 ppm. Also, the abnormal (n-type) semiconducting behavior and gas sensing mechanism are discussed in detail in the talk.