Influence of Oxygen Vacancies and Surface Facets on Water Oxidation Selectivity toward Oxygen or Hydrogen Peroxide with BiVO₄

Abstract

Bismuth vanadate (BiVO4) is one of the most promising photoanode materials for water oxidation. However, the water oxidation mechanism and selectivity on the different surfaces of BiVO4 are still not well understood, partly because of the structural complexity introduced by the presence of oxygen vacancies in the material. Using density functional theory, we show that the (001) surface of BiVO4 with subsurface vacancies is the most suitable for the oxygen evolution reaction, whereas the pristine (011) surface favors the hydrogen peroxide evolution reaction. A mechanism by which the vacancies can be removed from the surface, thereby influencing the water oxidation selectivity, is also described. Our results thus emphasize the crucial impact of the local structure on the catalytic selectivity in ternary oxides.

Promoting effects of Y doping and FeOOH loading for efficient photoelectrochemical activity on BiVO4 electrodes

“…3 The oxide semiconductor bismuth vanadate (BiVO 4 ) has been regarded as an ideal photoelectrode material for PEC water oxidation due to its narrow bandgap energy, suitable valence band position, low onset potential, and non-toxicity. 4–6 However, the photocurrent densities reported for pure BiVO 4 photoanodes are far below their theoretical value of 7.5 mA cm −2 (AM1.5G, 100 mW cm −2 ). This is mainly because it is inherently poor at separating and transporting charge carriers, has slow water oxidation kinetics, and undergoes serious surface recombination.…”

Mixed excitonic nature in water-oxidized BiVO$_4$ surfaces with defects

“…In this structure the GW gap of 2.9 eV is significantly smaller than in the pristine case. We associated this gap reduction to a partial state charging at the CBM region, responsible for the instability of this structure 25 . Notably, upon oxidation of the defect surface (Fig.…”

“…Despite these appealing properties, electron conductivity and carrier transport through BiVO 4 surfaces is found to be relatively low [13][14][15] , greatly limiting its use in practical applications. This low conductance is typically attributed to fast charge recombination and polaronic interactions 16,17 , strongly coupled to surface structure [18][19][20][21][22][23][24][25] and the conditions in which it was prepared 9,19,26,27 . A broadlyexplored pathway to improve BiVO 4 functionality is through electronic doping upon element substitution and the introduction of surface vacancies near the interacting BiVO 4 surface 16,18,28,29 .…”

“…Recent density functional theory (DFT) studies found that a structurally-stable split oxygen vacancy, in which the vacancy is shared between two neighboring vanadium atoms in the form of a V-O-V bridge, is pivotal to the catalytic reaction that produces molecular oxygen upon water adsorption at the thermodynamically-stable (001) BiVO 4 surfaces 25,35 . These studies showed that the change in surface structure and the underlying chemical bonding due to oxygen vacancies strongly depend on the adsorbate.…”

“…The calculated unit cell includes six layers, each containing four Bi and four V atoms, with a vacuum of 14 Å separating repeating cells along the ĉ direction (see SI). We considered four structures occurring within two oxidation pathways, recently suggested to play a key role within the photocatalytic cycle 25 : a pristine BiVO 4 surface (Fig. 1a); the same system after one water molecule per cell went through oxidation, resulting in a surface-peroxo group (Fig.…”