resumo
Hydrothermally obtained alpha-MnO2 nanowire characterizations confirm the tetragonal crystalline structure that is several micrometers long and 20-30 nm in diameter with narrow distributions in their dimensions. The absorption calculated from diffuse reflectance of alpha-MnO2 occurred in the visible region ranging from 400 to 550 nm. The calculated band gap with Quantum Espresso using HSE approximation is similar to 2.4 eV for the ferromagnetic case, with a slightly larger gap of 2.7 eV for the antiferromagnetic case, which is blue-shifted as compared to the experimental. The current work also illustrates the transformations that occur in the material under heat treatment during TGA analysis, with the underlying mechanism. Electrochemical studies on graphite supports modified with alpha-MnO2 compositions revealed the modified electrode with the highest electric double-layer capacitance of 3.444 mF cm(-2). The degradation rate of an organic dye-rhodamine B (RhB)-over the compound in an acidic medium was used to examine the catalytic and photocatalytic activities of alpha-MnO2. The peak shape changes in the time-dependent visible spectra of RhB during the photocatalytic reaction were more complex and progressive. In two hours, RhB degradation reached 97% under sun irradiation and 74% in the dark.
palavras-chave
RHODAMINE-B; PHOTOCATALYTIC ACTIVITY; MANGANESE OXIDES; MNO2; OXIDATION; DEGRADATION; DYE; NANOSTRUCTURES; PERFORMANCE; MECHANISMS
categoria
Chemistry; Engineering; Materials Science; Physics
autores
Taranu, BO; Novaconi, SD; Ivanovici, M; Goncalves, JN; Rus, FS
nossos autores
João Nuno Santos Gonçalves
Investigador Júnioragradecimentos
This work was supported by the Ministry of Research and Innovation from PN 19 22 01 01 projects, with contract number 40N/2019. The ab initio calculations were performed under the project HPC-EUROPA3 (INFRAIA-2016-1-730897), with the support of the EC Research Innovation Action under the H2020 Programme; in particular, the authors gratefully acknowledge the support of Alessandro Stroppa and the hospitality from CNR-SPIN c/o Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio, I-67100, Coppito, L'Aquila, Italy. We are grateful for the computer resources and technical support provided by CINECA.