Thermal Stability and Utilization of 1D-Nanostructured Co3O4 Rods Derived by Simple Solvothermal Processing

Abstract

For p-type semiconductor nanoparticles, such as the cobalt oxide spinel, enhancing the nanoparticle geometry can expose more of the surface and bring up the sensitivity and applicability, pointing to even more advantageous behaviour in comparison to n-type semiconductors which are known for a somewhat faster reactivity. Here, we present a strategy that relies on fostering a simple synthetic route that can deliver reasonably or comparably performing p-type-semiconducting partially 1D-Co3O4 material prepared under less technically and economically demanding conditions. Structurally monophasic Co3O4 nanoparticles with a spinel structure were indicated by powder X-ray diffraction, while the presence of traces of organic-phase residuals in otherwise chemically homogeneous material was observed by Fourier-transform infrared spectroscopy. Scanning electron microscopy further showed that the observed fine nanoparticle matter formed agglomerates with the possible presence of rod-like formations. Interestingly, using transmission electron microscopy, it was possible to reveal that the agglomerates of the fine nanoparticulated material were actually nanostructured, i.e., the presence of 1D-shaped Co3O4 rods embedded in fine nanoparticulated matrix was confirmed. In conjunction with the N2 adsorption–desorption isotherms, discussion about the orientation, exposure of nanostructured rod domains, and derivative geometry parameters was possible. The nanostructured Co3O4 material was shown to be stable up to 800 °C whereat the decomposition to CoO takes place. The specific surface area of the nanostructured sample was raised. For the purpose of testing the photoactivity of the prepared samples, simple sorption/photodegradation tests using methylene blue as the model pollutant were performed. The degradation performance of the prepared nanostructured Co3O4 was better described by a pseudo-second-order fit, suggesting that the prepared material is worth further development toward improved and stable immobilized photocatalysts.