All-Solution-Processed WO₃/BiVO₄ Core–Shell Nanorod Arrays for Highly Stable Photoanodes

Abstract

Tungsten oxide (WO 3 ) and bismuth vanadate (BiVO 4 ) are one of the most attractive combinations to construct an efficient heterojunction for photoelectrochemical (PEC) applications. Here, we report an all-solution-processed WO 3 /BiVO 4 heteronanostructure photoanode with highly enhanced photoactivity and stability for sustainable energy production. The vertically aligned WO 3 nanorods were synthesized on a fluorine-doped tin oxide/glass substrate by the hydrothermal method without a seed layer and BiVO 4 was deposited by pulsed electrodeposition for conformal coating. Owing to the long diffusion lengths of charge carriers in the WO 3 nanorods, the ability to absorb the wider range of wavelengths, and appropriate band-edge positions of the WO 3 /BiVO 4 heterojunction for spontaneous PEC reaction, the optimum WO 3 /BiVO 4 photoanode has a photocurrent density of 4.15 mA/cm 2 at 1.23 V versus RHE and an incident-photonto-current efficiency of 75.9% at 430 nm under front illumination, which are a double and quadruple those of pristine WO 3 nanorod arrays, respectively. Our work suggests an environment-friendly and low-cost all-solution process route to synthesize high-quality photoelectrodes.

Planar and Nanostructured n‐Si/Metal‐Oxide/WO3/BiVO4 Monolithic Tandem Devices for Unassisted Solar Water Splitting

“…Fringes observed in regions of the nanorod core have an average interplanar spacing of 0.385 nm, matching well with the d‐spacing between the (002) planes of the monoclinic‐WO 3 structure. [ 32 ] Along the same axis of this nanorod and for the majority of the WO 3 nano /BiVO 4 interfaces, there was a consistent orientation between the BiVO 4 (130)‐WO 3 (002) planes with an acute angle of ≈70 o , providing evidence for a preferred orientation for this particular lattice arrangement for the monoclinic BiVO 4 structure grown on monoclinic WO 3 .…”

“…A range of electrochemical, chemical, and physical deposition techniques have been used for the successful fabrication of WO 3 /BiVO 4 core shell nanostructures. [ 28,32,36–38 ] Here we have utilized a simplified solution deposition method, which was previously developed within our group (see Figure S8, Supporting Information). [ 39 ] This consecutive BiVO 4 solution deposition method is effective and completely encapsulates the WO 3 nano nanorods with BiVO 4 (see Figure S9, Supporting Information), providing a viable and reproducible approach to form WO 3 nano /BiVO 4 core shell nanostructures.…”

“…3) Core‐shell WO 3 /BiVO 4 nanostructured heterojunctions as the top absorber—The core‐shell nanostructure architecture with high aspect ratio is an effective approach to mitigate the impact of poor charge transport and low light absorption in BiVO 4 ; high photocurrents (up to ≈7 mA cm −2 under 1 sun illumination) have been previously reported with such samples. [ 28–32 ] In this study, we control the reactor temperature during AA‐CVD to manipulate the morphology of the deposited WO 3 ; reaction rate‐limited growth at “low” temperatures favor planar film growth, while diffusion‐limited growth at “high” temperatures favor nano‐structured growth. [ 33,34 ] The process is combined with the spin‐coating of BiVO 4 .…”

“…It is demonstrated that this simple fabrication method can generate the same intricate nanostructured core‐shell WO 3 /BiVO 4 heterojunctions as the ones previously reported in the literature. [ 28,31,32 ]…”

Influence of C3N4 Precursors on Photoelectrochemical Behavior of TiO2/C3N4 Photoanode for Solar Water Oxidation

“…Semiconductors with staggered band alignments can be coupled to fabricate the heterojunction, which can improve the solar water oxidation of the photoelectrode due to the increased charge carrier separation [7][8][9][10][11]. Nano structural modification with high surface area is beneficial to further improve the photocurrent density of the heterojunctions [12,13].…”