Microwave-assisted synthesis of Ca1-xMnxMoO4 (x = 0, 0.2, 0.7, and 1) and its application in artificial photosynthesis. Issue 4 (15th February 2021)

• Record Type: Journal Article
• Authors: Júnior, Roberto C.da S.; Nogueira, André E.; Giroto, Amanda S.; Torres, Juliana A.; Ribeiro, Caue; Siqueira, Kisla P.F.
• Is Part Of: Ceramics international. Volume 47:Issue 4(2021)
• Page Start: 5388
• Page End: 5398
• Publication Date: 2021-02-15
• Subjects: Artificial photosynthesis -- Microwave-assisted hydrothermal method -- Molybdates -- Doping -- Heterostructures; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2020.10.119
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: This work reports, for the first time, to the best of our knowledge, the use of calcium molybdates doped with Mn 2+ in the catalytic photoreduction of CO2 to produce compounds with higher added value that have applications in different branches of the chemical industry. The molybdates were prepared at 100 °C by microwave-assisted hydrothermal synthesis and were characterized by X-ray diffraction, Raman vibrational spectroscopy, scanning electron microscopy, and diffuse UV–vis reflectance spectroscopy. The synthesized Ca1-x Mnx MoO4 catalysts (x = 0, 0.2, 0.7, and 1) were also calcined at 500 °C, in order to investigate possible phase transitions. For x = 0 and 0.2, the samples crystallized in the tetragonal structure (I41 /a, #88) and no phase transitions were observed at 500 °C. For x = 0.7 and 1.0, the phase produced at 100 °C was a hydrated form of manganese molybdate that exhibited triclinic structure ( P 1 ‾, #2) and became monoclinic (C2/m, #12) when calcined at 500 °C. The catalysts subsequently investigated were the pure molybdate and the materials with doping contents of 20 and 70 mol% Mn 2+, hydrothermally treated at 100 °C and after calcination at 500 °C. The band gap energies ranged from 2.77 to 3.50 eV. In the performance tests, the productions of CO and CH4 after 6 h of irradiation were in the ranges 2.41–19.74 and 0.21–0.82 μmol g −1, respectively. The doped x = 0.2 sample treated at 100 °C exhibited the best performance, producing the highest amounts of CO and CH4 . The results indicated that the doping of CaMoO4 with Mn 2+ improved the performance of this ceramic for the purpose of artificial photosynthesis. Furthermore, our results support a deep discussion about the role of doping content and crystalline structure of the molybdates on the photocatalytic activity. Graphical abstract: The doping of calcium molybdates by Mn 2+ improves the performance of these ceramics for purpose of artificial photosynthesis. The effects of doping, heterostructure formation, and thermal treatment were investigated using Ca1-x Mnx MoO4 (x = 0; 0.2; 0.7 and 1) photocatalysts. Image 1