Nanostructured WO₃/BiVO₄ Photoanodes for Efficient Photoelectrochemical Water Splitting

Abstract

Nanostructured photoanodes based on well-separated and vertically oriented WO3 nanorods capped with extremely thin BiVO4 absorber layers are fabricated by the combination of Glancing Angle Deposition and normal physical sputtering techniques. The optimized WO3 -NRs/BiVO4 photoanode modified with Co-Pi oxygen evolution co-catalyst shows remarkably stable photocurrents of 3.2 and 5.1 mA/cm(2) at 1.23 V versus a reversible hydrogen electrode in a stable Na2 SO4 electrolyte under simulated solar light at the standard 1 Sun and concentrated 2 Suns illumination, respectively. The photocurrent enhancement is attributed to the faster charge separation in the electronically thin BiVO4 layer and significantly reduced charge recombination. The enhanced light trapping in the nanostructured WO3 -NRs/BiVO4 photoanode effectively increases the optical thickness of the BiVO4 layer and results in efficient absorption of the incident light.

Efficient Water Splitting Cascade Photoanodes with Ligand‐Engineered MnO Cocatalysts

“…The BF 4 ‐treated MnO/BiVO 4 /WO 3 anode achieved 6.25 mA cm −2 at the 1.23 V versus RHE. We emphasize that the photocurrent of BF 4 ‐treated MnO attached to the BiVO 4 /WO 3 anode is the highest of the previously reported BiVO 4 ‐based photoanodes with hole scavenger for solar water splitting, as shown in Table S2 and Figure S4 (Supporting Information) 13, 14, 16, 17, 21, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69. Otherwise, Ca–EDTA‐treated MnO NPs/BiVO 4 /WO 3 recorded the lowest photocurrent density of about 2.5 mA cm −2 .…”

“…In the sulfite oxidation with extremely fast oxidation kinetics, in other words, Na 2 SO 3 removing the injection barrier without affection the charge separation, surface recombination can be negligible. Therefore, most of the previously reported results related to BiVO 4 ‐based photoanodes13, 14, 16, 19, 47, 51, 52, 53 were measured in sulfite oxidation condition to show photo‐electrochemical properties of BiVO 4 ‐based electrodes independently of its poor water oxidation kinetics, as shown in Table S2 (Supporting Information). The photo‐electrochemical current densities of the BiVO 4 ‐based photoanodes4, 13, 14, 16, 17, 19, 20, 21, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 77 were plotted as a function of potential versus RHE.…”

Atomic Layer Deposition of Bismuth Vanadates for Solar Energy Materials

“…The ALD of bismuth vanadates is a key step towards its development into host-guest composite nanostructures. Hostguest architectures have been attempted with BiVO 4 ; however, all reports suffered from either non-uniform depositions [38][39][40]48] or used cathodic deposition [49] that limited the use of holeblocking layers at the interface of the host and the guest. [21,53] Here, ALD brings a significant advantage in that controlled films may be grown on arbitrary 3D porous scaffolds.…”

Recent Advances in Nanostructured Vanadium Oxides and Composites for Energy Conversion

“…The energy gradient at the interfaces of type-II heterostructures could assist the separation of electron-hole pairs, and spatially localize the electrons and holes on different sides of the heterojunction. The BiVO 4 -based type-II heterostructures have attracted numerous attentions and been prepared in many forms, such as BiVO 4 /Bi 2 S 3 , [254] BiVO4/Ag 3 PO 4 , [255] BiVO4/g-C3N 4 , [256] BiVO 4 /WO 3 , [257] TiO 2 /BiVO 4 [258] and MoS 2 /BiVO 4 . [259] These studies have verified that the photocatalytic properties can be improved by type-II heterojunctions, which exhibit enhanced charge separation efficiency and isolated redox reaction sites.…”