SILAR deposition of bismuth vanadate photoanodes for photoelectrochemical water splitting

Abstract

Bismuth vanadate coatings are fabricated via a sequential solution-based method and used as photoanodes for water oxidation achieving exceptional performances.

Nanostructured Electrodes Based on Two-Dimensional SnO2 for Photoelectrochemical Water Splitting

“…The optical band gaps of combined films were estimated from the absorption spectra using Tauc analysis assuming direct allowed transitions, obtaining values between 2.6 and 2.7 eV for all samples prepared in this study (Table S2). Slightly lower band gap values were obtained for thicker samples, in agreement with our previous work …”

“…Distinct peaks were observed at 164.3 and 159.0 eV, corresponding to Bi 4f 5/2 and Bi 4f 3/2 , respectively. The binding energy of these single-component peaks is consistent with the +3 oxidation state of bismuth as an oxide and are in agreement with existing literature of SILAR - BiVO 4 . , V 2p 1/2 and V 2p 3/2 peaks were detected at 524.3 and 516.7 eV, and substantiate the presence of vanadium in its +5 oxidation state, as expected. , The O 1s peak is observed to be highly asymmetric in shape and could only be effectively fitted with five peaks corresponding to five separate chemical environments. The most intense peak components (529.7 and 530.7 eV) correspond to metal oxides and hydroxyls on the surface of the SnO 2 /BiVO 4 , respectively.…”

“…This latter process, known as the oxygen evolution reaction (OER), is the critical step in water splitting because it is a four-electron process and is widely accepted as the bottleneck in the overall reaction. , As such, the development of electrode materials able to effectively promote OER at the photoanode is vital if PEC water splitting is to become a viable industrial process. Many semiconducting materials with a suitable band gap in the visible range enabling solar light harvesting have been studied as photoelectrodes for water splitting devices. , However, the fabrication of highly efficient photoanodes for OER has proved challenging because of the large driving force required to oxidize water, and the intrinsic problems of photoanode materials including charge recombination and poor charge transport. , Metal oxides such as TiO 2 , WO 3 , Fe 2 O 3 , and BiVO 4 , are all advantageous photoanode materials because of their high chemical and thermal resistance and their high theoretical PEC efficiencies, especially in the case of iron oxide and bismuth vanadate, which both possess a suitable band gap and band positions for OER. Several strategies have been adopted to further improve the properties of these materials, including doping, facet and morphology engineering, surface decoration, and band gap tuning .…”

“…Bismuth vanadate (BiVO 4 ) was chosen as the light active material due to its well-known activity and suitable band gap for the oxygen evolution reaction (OER). , BiVO 4 was deposited on 2D SnO 2 via the SILAR (successive ionic layer absorption and reaction) technique as detailed in the methods section, wherein the concentration of the precursors and the number of SILAR cycles was varied. We have previously demonstrated the interplay of these parameters to control the properties of BiVO 4 …”

Sustainable photoanodes for water oxidation reactions: from metal-based to metal-free materials

“…On the basis of the appropriate thermodynamic properties for the water oxidation reaction, a few other issues were attempted to be addressed, such as photoexcitation charge separation and transfer, surface reaction, and stability. [87][88][89] For instance, Kuang and co-workers have attempted to improve the stability of BiVO 4 -based photoanode for OER. 90 They attempted to load Ni 2+ and Fe 2+ ions on the surface of BiVO 4 films as the photoanode.…”