Enhanced optical and electrochemical properties of FeBTC MOF modified TiO2 photoanode for DSSCs application
William Moloto, Pontsho Mbule, Edward N. Nxumalo, Bulelwa Ntsendwana
Abstract
Abstract In this work, iron based 1, 3, 5-tricarboxylic acid (FeBTC) was prepared via microwave-assisted method and incorporated into TiO 2 via ultrasonic assisted method. The TiO 2 –FeBTC nanocomposites were characterized by XRD, FTIR, Raman, BET, FESEM, HRTEM, TGA, UV‒vis DRS and PL to understand their crystallographic, surface morphology, and optical characteristics. The Raman spectra showed a blue shift of E g , A 1g , and B 1g peaks upon incorporation of FeBTC MOF onto TiO 2 . HRTEM and XRD analysis confirmed a mixture of TiO 2 nanospheres and hexagonal FeBTC MOF morphologies with high crystallinity. The incorporation of FeBTC onto TiO 2 improved the surface area as confirmed by BET results, which resulted in improved absorption in the visible region as a results of reduced bandgap energy from 3.2 to 2.84 eV. The PL results showed a reduced intensity for TiO 2 –FeBTC (6%) sample, indicating improved separation of electron hole pairs and reduced recombination rate. After fabrication of the TiO 2 –FeBTC MOF photoanode, the charge transfer kinetics were enhanced at TiO 2 –FeBTC MOF (6%) with Rp value of 966 Ω, as given by EIS studies. This led to high performance due to low charge resistance. Hence, high power conversion efficiency (PCE) value of 0.538% for TiO 2 –FeBTC (6%) was achieved, in comparison with other loadings. This was attributed to a relatively high surface area which allowed more charge shuttling and thus better electrical response. Conversely, upon increasing the FeBTC MOF loading to 8%, significant reduction in efficiency (0.478%) was obtained, which was attributed to sluggish charge transfer and fast electron–hole pair recombination rate. The TiO 2 –FeBTC (6%) may be a good candidate for use in DSSCs as a photoanode materials for improved efficiency.