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. 2023 Nov 15;15(45):52436-52447.
doi: 10.1021/acsami.3c10869. Epub 2023 Nov 3.

Improved Photoelectrochemical Performance of WO3/BiVO4 Heterojunction Photoanodes via WO3 Nanostructuring

Chiara Nomellini  1 , Annalisa Polo  1 , Camilo A Mesa  2 , Ernest Pastor  2   3 , Gianluigi Marra  4 , Ivan Grigioni  1 , Maria Vittoria Dozzi  1 , Sixto Giménez  2 , Elena Selli  1
Affiliations

Improved Photoelectrochemical Performance of WO3/BiVO4 Heterojunction Photoanodes via WO3 Nanostructuring

Chiara Nomellini et al. ACS Appl Mater Interfaces. .

Abstract

WO3/BiVO4 heterojunction photoanodes can be efficiently employed in photoelectrochemical (PEC) cells for the conversion of water into molecular oxygen, the kinetic bottleneck of water splitting. Composite WO3/BiVO4 photoelectrodes possessing a nanoflake-like morphology have been synthesized through a multistep process and their PEC performance was investigated in comparison to that of WO3/BiVO4 photoelectrodes displaying a planar surface morphology and similar absorption properties and thickness. PEC tests, also in the presence of a sacrificial hole scavenger, electrochemical impedance analysis under simulated solar irradiation, and incident photon to current efficiency measurements highlighted that charge transport and charge recombination issues affecting the performance of the planar composite can be successfully overcome by nanostructuring the WO3 underlayer in nanoflake-like WO3/BiVO4 heterojunction electrodes.

Keywords: bismuth vanadate; heterojunction; nanostructuring; photoanodes; tungsten trioxide; water oxidation.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) Absorption spectra and (b) XRD patterns of planar and nanostructured WO3, WO3/BiVO4, and BiVO4 electrodes. The diffraction signals of WO3 (JCPDS 05–0363) and BiVO4 (JCPDS 75–1867) are reported for comparison; the peaks marked with an asterisk refer to FTO.
Figure 2
Figure 2
Top-view SEM images of (a) WO3_NF, (b) WO3_NF-BV, (c) WO3_P, and (d) WO3_P-BV electrodes; the scale bar is 1 μm. Cross-section SEM images of (e) WO3_NF, (f) WO3_NF-BV, (g) WO3_P, and (h) WO3_P-BV electrodes; the scale bar is 500 nm.
Scheme 1
Scheme 1. Schematic Illustration of (A) Nanostructured and (B) Planar WO3 and WO3/BiVO4 Photoanodes
Figure 3
Figure 3
Linear sweep voltammetry (LSV) curves recorded with nanostructured and planar WO3, WO3/BiVO4, and BiVO4 electrodes, under (a, b) back-side and (c, d) front-side irradiation in 0.5 M Na2SO4.
Scheme 2
Scheme 2. Schematic Illustration of the Irradiation Wavelength-Dependent Charge Recombination (Red Arrows) or Charge Separation (Blue Arrows) Paths at Work at WO3/BiVO4 Heterojunctions, under (A) Back-Side and (B) Front-Side Irradiation
Figure 4
Figure 4
(a) Nyquist plots recorded with WO3_P (blue), WO3_NF (green), WO3_NF-BV (purple), and WO3_P-BV (orange) under 1 sun back-side irradiation, at 1.23 VRHE. Inset: Randles circuit. (b) Total resistance Rdc and (c) surface capacitance C of the same electrodes. The data obtained with WO3_P–BV could be fitted only for applied potentials above 1 VRHE.
Figure 5
Figure 5
Incident photon to current efficiency (IPCE) curves obtained with (a) WO3 and (b) WO3/BiVO4 and BiVO4 electrodes at 1.23 VRHE in Na2SO4 0.5 M solution under back-side (full symbols) and front-side (open symbols) irradiation.
Figure 6
Figure 6
(a) IPCE enhancement factor calculated according to eq 3. (b) Charge injection (continuous lines) and charge separation efficiency (dashed lines) of the nanostructured (purple) and planar (orange) WO3/BiVO4 heterojunctions.
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