Freeing the Polarons to Facilitate Charge Transport in BiVO₄ from Oxygen Vacancies with an Oxidative 2D Precursor

Abstract

The BiVO4 photoelectrochemical (PEC) electrode in tandem with a photovoltaic (PV) cell has shown great potential to become a compact and cost‐efficient device for solar hydrogen generation. However, the PEC part is still facing problems such as the poor charge transport efficiency owing to the drag of oxygen vacancy bound polarons. In the present work, to effectively suppress oxygen vacancy formation, a new route has been developed to synthesize BiVO4 photoanodes by using a highly oxidative two‐dimensional (2D) precursor, bismuth oxyiodate (BiOIO3), as an internal oxidant. With the reduced defects, namely the oxygen vacancies, the bound polarons were released, enabling a fast charge transport inside BiVO4 and doubling the performance in tandem devices based on the oxygen vacancy eliminated BiVO4. This work is a new avenue for elaborately designing the precursor and breaking the limitation of charge transport for highly efficient PEC‐PV solar fuel devices.

First-Principle Insight Into the Effects of Oxygen Vacancies on the Electronic, Photocatalytic, and Optical Properties of Monoclinic BiVO4(001)

“…The ESR spectrum of BiVO 4 -Ovac exhibits a fingerprint signal at about g = 2.0 ( Figure 6) (Shi et al, 2018;Qiu et al, 2019), which proved the existence of Ovac. The signal decreased as the calcination time increased, suggesting Ovac were removed during the high-temperature annealing process.…”

Activity and Stability Boosting of an Oxygen‐Vacancy‐Rich BiVO4 Photoanode by NiFe‐MOFs Thin Layer for Water Oxidation

“…The oxygen vacancy is a type of defect that is ubiquitous in metal oxides and has sparked considerable research interests in recent years [4] . The exact impact of oxygen vacancy on PEC performance is still ambiguous and poorly understood [4b, 5] . Nonetheless, many researchers believe that it could act as a shallow donor to induce defect states in the forbidden band, thus enhancing the conductivity and potentially creating active sites for water splitting [4c, 6] .…”

Boosting Charge Transport in BiVO4 Photoanode for Solar Water Oxidation

“…[11][12][13][14] To inhibit the polaron formation, researchers have made many attempts, such as heteroatom doping, oxygen vacancy control, etc. [15][16][17][18] However, the electron and hole polarons of the BiVO 4 are localized in VO 4 units and BiO 8 units, respectively, [15][16][17][18][19] these previous attempts by heteroatom doping (substituting V atom), oxygen vacancies control, etc., that are suggested to be efficient for alleviating bulk recombination might only promote the electron migration, while the hole transport is scarcely tackled. As a result, appropriately altering the BiO 8 unit surrounded hole polaron is highly expected to address the bulk charge transport issue of BiVO 4 at root, but no developable method is reported yet.…”