Factors in the Metal Doping of BiVO₄ for Improved Photoelectrocatalytic Activity as Studied by Scanning Electrochemical Microscopy and First-Principles Density-Functional Calculation

Abstract

Metal doping of the metal oxide photoelectrocatalyst, BiVO4, dramatically increases its activity for water oxidation. Scanning electrochemical microscopy (SECM) was used to screen various dopants for their photoelectrochemical performance and to optimize the used dopant material concentrations with this photocatalyst. For example, adding Mo to W-doped BiVO4 enhanced the performance. The photocatalytic activity was examined on larger electrodes by means of photoelectrochemical and electrochemical measurements. The developed photoelectrocatalyst, W- and Mo-doped BiVO4, shows a photocurrent for water oxidation that is more than 10 times higher than undoped BiVO4. Factors that affect performance are discussed, and enhanced separation of excited electron–hole pairs by doping onto the semiconductor is suggested by first-principles density-functional theory (DFT) calculations. Distortion of the crystal structure of monoclinic scheelite-like BiVO4 by addition of W and Mo doping predicted by DFT is also revealed by X-ray diffraction and Rietveld refinement analysis. The results indicate that the consecutive doping of W and Mo into the metal oxide photocatalyst introduces improved electron–hole separation without a significant change of the band gap or the material's optical properties.

Structural and electronic properties of oxygen defective and Se-doped p-type BiVO4(001) thin film for the applications of photocatalysis

“…Contribution of the s, p, and d orbitals of Bi, V, and O, in making the band gap and edge positions are given in Fig. 3, where an indirect band gap of 2.24 eV has good agreement with the experimental and recently theoretical reported data [9]. Fruthermore, the simulated band edge energies (VBM ∼−6.80 and CBM ∼−4.56 eV at vacuum level) of BiVO 4 indicate that its CBM need to be engineered for high PEC performance.…”

“…As discussed in our previous report [29], that the monoclinic clinobisvanite phase exhibits a much higher photocatalytic activity compared to its other polymorphs due to its favourable band gap (2.4−2.5 eV) in the visible region of electromagnetic spectrum and a valence band position suitable for driving water oxidation [9].…”

“…These different polymorphs have different properties as the photocatalytic activity is strongly influenced by the crystal structure. For instance, the tetragonal BiVO 4 possesses a band gap of 2.9 eV and mainly absorbs UV region, while the monoclinic clinobisvanite (m-BiVO 4 ) exhibits a much higher photocatalytic activity due to its ideal band gap (2.4−2.5 eV) which absorb the UV and visible regions of the electromagnetic spectrum, having an ideal valence band edge position for driving water oxidation [9]. However, it has been recently reported that m-BiVO 4 , an n-type semiconductor [10], exhibits poor photocatalytic property which is stem to low mobility of the photogenerated charge carriers (electron−hole pairs), positive potential of CB (vs NHE) and high charge recombination rates which significantly limit its practical applications.…”

Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures

“…The effect of metal doping on the properties of BiVO 4 has been well investigated, with consecutive doping of W and Mo into BiVO 4 ((W, Mo)-BiVO 4 ) resulting in superior photochemical performance 17,18 . In this study, (W, Mo)-BiVO 4 was used as a guest material to produce highly efficient PEC cells based on WO 3 helix nanostructures.…”

Anisotropic small-polaron hopping in W:BiVO4 single crystals

“…[1][2][3] However, the low electrical conductivity of BVO limits its utility as a photo-electrode. [4][5][6] This low conductivity was preliminarily ascribed to its charge carriers forming small polarons and a low temperature-independent Hall mobility. 4 Small polarons can form when electronic charge carriers move slowly enough to displace surrounding atoms from their equilibrium positions.…”