Evaluation of the Parameters Affecting the Visible-Light-Induced Photocatalytic Activity of Monoclinic BiVO₄ for Water Oxidation

Abstract

Monoclinic BiVO 4 powders have been synthesized by means of homogeneous coprecipitation, followed by calcination at different temperatures. The effect of the calcination temperature on the changes in the physicochemical parameters has been evaluated. It has been deduced that the crystallite size and band gap are responsible for water oxidation. The effect of calcination temperatures on the variations, such as lone pair distortions on Bi 3+ and changes in the V−O bond length in the local structure of BiVO 4 , has also been confirmed from the changes in the intensities and the shift of the peak position in the Raman analysis.

Recent Advances in the BiVO4 Photocatalyst for Sun-Driven Water Oxidation: Top-Performing Photoanodes and Scale-Up Challenges

“…The crystallite size was found to have a direct correlation to the O 2 production activity of BiVO 4 samples [62] (i.e., doubling the size of the BiVO 4 crystals, from 90 to 170 nm increased the rate of O 2 evolution in 5-fold). The preferential orientation towards the {040} facets with respect to the {110} exposed surfaces, is known to have a positive influence on the water oxidation photoactivity of scheelite monoclinic BiVO 4 [63].…”

“…On the other hand, Thalluri et al [62] identified the important role of the superficial amounts of W and Mo dopants for the water oxidation reaction. They determined that charge carriers separation is enhanced on the surface of BiVO 4 for up to a certain amount of such dopants: 0.9 at.% of W or 1.2 at.% of Mo, for which the superficial electron-hole recombination is reduced, and in turn, the BiVO 4 photocatalytic activity is improved.…”

Green-synthesized W- and Mo-doped BiVO4 oriented along the {0 4 0} facet with enhanced activity for the sun-driven water oxidation

“…However, regardless of this, this kind of experiment is usually performed since it is useful to compare the rate of oxygen production (RO 2 ) of the different samples [41][42][43]. The RO 2 of all the samples was calculated through the slope of the cumulative curves in the first 5 minutes of each measurement, and the results are reported in the Table 1 In our previous works, it was observed that the O 2 evolution activity of BiVO 4 had a direct correlation (in order or importance) with the crystallite size, band gap and the ratio between the {040} and {110} facets [13,28]. However, when the O 2 evolution rates of the BiVO 4 , W-BiVO 4 -1 and Mo-BiVO 4 -2 samples (which have similar particles sizes) are compared, it is evident that the crystallites size cannot be correlated to the enhanced activity in the doped materials.…”

“…Monoclinic BiVO 4 has attracted considerable attention, owing to its water splitting [13] and organic dye degradation [14] photoactivities under visible light illumination. In 1998, Kudo's group first reported monoclinic BiVO 4 that showed promising water oxidation activity under visible light illumination [15].…”

“…It has been shown that there are facet-dependent characteristics in BiVO 4 that can lead to a higher water oxidation activity, with the {010} facet being regarded as the most active facet, due to its different surface-related properties [26,27]. However, this property has only been experimentally verified in a few papers [13,26,28]. Only a few studies have been dedicated to a methodological growth of BiVO 4 crystals with different shapes, in order to compare their photoelectrochemical and photocatalytic properties [6,14,29,30].…”