Mn-modified Bi₂Ti₂O₇ photocatalysts: bandgap engineered multifunctional photocatalysts for hydrogen generation

Abstract

In this study, a hydrogen generation photocatalyst based on bismuth titanate (Bi2Ti2O7 - BTO) modified with manganese (Mn) has been developed. Mn of varying weight percent was added to construct a modified BTO catalyst (Mn_BTO), in order to enhance the opto-electronic and photocatalytic hydrogen generation capabilities of the pristine BTO. The structural, morphological, and optical properties of the photocatalysts were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-visible spectrophotometry. The XRD, SEM, and TEM analyses indicate the formation of the pyrochlore BTO phase with particles of dimensions 30 ± 10 nm. The UV-visible study revealed a reduction in the bandgap of Mn_BTO and enhanced absorption in the visible range, compared to the pristine BTO. The catalyst was optimized for maximum hydrogen generation from a water-methanol (sacrificial electron donor) system in a slurry reactor. The photocatalytic hydrogen evolution studies indicate that the Mn_BTO with up to 1 wt% Mn facilitates an optimal 140% increase in the hydrogen yield. The role of formic acid and formaldehyde as additives in photocatalytic hydrogen evolution has also been examined. The effect of Mn content, mechanistic overview, and reusability of the catalyst are discussed.

A Facile Method for the Preparation of Colored Bi4Ti3O12−x Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Evolution Activity

“…It can be seen that the H 2 evolution rate for formic acid reaches 218 μmol·g −1 ·h −1 , which is much higher than that for methanol and formaldehyde. It is assumed that this phenomenon is due to the low dissociation energy (−95.8 kJ·mol −1 ) of formic acid that is much smaller than that of methanol (64.1 kJ·mol −1 ) and formaldehyde (47.8 kJ·mol −1 ) [ 42 , 47 ]. Therefore, the –COOH group of formic acid can dissociate spontaneously [ 42 ], which results in a large hydrogen evolution rate.…”

Free energy landscape approach to aid pure phase synthesis of transition metal (X=Cr, Mn and Fe) doped bismuth titanate (Bi2Ti2O7)

“…) with pyrochlore structure has been studied as a photocatalyst that can be used to convert solar energy into H 2 and O 2 (fuels) from water [37][38][39][40][41][42][43][44][45][46][47][48]. [41], and due to the presence of active Bi 6s lone pairs, the unoccupied Bi 6p states are strongly coupled with Ti 3d antibonding states.…”

A Selective Synthesis of TaON Nanoparticles and Their Comparative Study of Photoelectrochemical Properties

“…Therefore, after the first use, the Ta2O5 photocatalyst was removed, washed, centrifuged, and dried in the presence of a positive draft of enriched oxygen at a temperature of 400 C. This oxidative approach has been shown earlier to aid in recovering most of the photoactivity of oxide catalysts [51]. The results of such a treatment followed by a second and a third use are shown in Figure 7 along with the performance of the pristine catalyst as a comparison.…”