Zero-Gap Tandem Photoelectrochemical Cell Based on Nanostructured WO3 and CuFe2O4 Photoelectrodes and a Proton-Exchange Membrane: Bias-Free Photoelectrochemical Operation and Degradation Analysis
- 1Institute for Advanced Energy Technologies “Nicola Giordano” (ITAE), National Research Council of Italy (CNR), Via Salita S. Lucia Sopra Contesse 5, 98126 Messina, Italy
Abstract
Tandem photoelectrochemical (PEC) cells made exclusively of earth-abundant oxides are a promising route to solar hydrogen, but bias-free operation and durability remain challenging, particularly in acidic environments. This work presents a 1 cm2 zero-gap tandem PEC cell, operated without housing and fed only with deionized water, that integrates an electrodeposited nanostructured WO3 photoanode (band gap 2.75 eV), a spray-coated nanostructured CuFe2O4 photocathode (1.43 eV) and a Nafion 117 proton-exchange membrane acting as solid electrolyte and separator. Mott–Schottky analysis in N2-purged 0.1 M HClO4 confirms the expected n-type and p-type semiconductor character, with a band-edge alignment compatible with unassisted operation. Under simulated AM 1.5G sunlight, the device delivers ≈42 µA cm−2 at zero bias (solar-to-hydrogen efficiency ≈ 0.05%, assuming unity Faradaic efficiency) and a saturated photocurrent density of 0.47 mA cm−2 at −1.0 V (throughput efficiency 0.70%). After 96 h of operation (48 h at 0 V and 48 h at −0.7 V), the photocurrent decreases by only ≈5–6%. Impedance spectroscopy and distribution of relaxation times analysis identify a dominant millisecond-scale interfacial charge-transfer process. Post-operando analyses reveal that WO3 undergoes only mild surface reduction, whereas CuFe2O4 shows partial Cu2+ → Cu+ reduction and local delamination, identifying the photocathode as the lifetime-limiting component.
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BibTeX
@article{giaquinta2026zerogap,
title = {{Zero-Gap Tandem Photoelectrochemical Cell Based on Nanostructured WO3 and CuFe2O4 Photoelectrodes and a Proton-Exchange Membrane: Bias-Free Photoelectrochemical Operation and Degradation Analysis}},
author = {Rossana Giaquinta and Carmine Arnese and Stefano Trocino},
journal = {Nanomaterials},
year = {2026},
month = nov,
doi = {10.3390/nano16211415},
url = {https://www.mdpi.com/2079-4991/16/21/1415},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Zero-Gap Tandem Photoelectrochemical Cell Based on Nanostructured WO3 and CuFe2O4 Photoelectrodes and a Proton-Exchange Membrane: Bias-Free Photoelectrochemical Operation and Degradation Analysis
AU - Rossana Giaquinta
AU - Carmine Arnese
AU - Stefano Trocino
PY - 2026
DA - 2026/11/03
JO - Nanomaterials
DO - 10.3390/nano16211415
UR - https://www.mdpi.com/2079-4991/16/21/1415
AB - Tandem photoelectrochemical (PEC) cells made exclusively of earth-abundant oxides are a promising route to solar hydrogen, but bias-free operation and durability remain challenging, particularly in acidic environments. This work presents a 1 cm2 zero-gap tandem PEC cell, operated without housing and fed only with deionized water, that integrates an electrodeposited nanostructured WO3 photoanode (band gap 2.75 eV), a spray-coated nanostructured CuFe2O4 photocathode (1.43 eV) and a Nafion 117 proton-exchange membrane acting as solid electrolyte and separator. Mott–Schottky analysis in N2-purged 0.1 M HClO4 confirms the expected n-type and p-type semiconductor character, with a band-edge alignment compatible with unassisted operation. Under simulated AM 1.5G sunlight, the device delivers ≈42 µA cm−2 at zero bias (solar-to-hydrogen efficiency ≈ 0.05%, assuming unity Faradaic efficiency) and a saturated photocurrent density of 0.47 mA cm−2 at −1.0 V (throughput efficiency 0.70%). After 96 h of operation (48 h at 0 V and 48 h at −0.7 V), the photocurrent decreases by only ≈5–6%. Impedance spectroscopy and distribution of relaxation times analysis identify a dominant millisecond-scale interfacial charge-transfer process. Post-operando analyses reveal that WO3 undergoes only mild surface reduction, whereas CuFe2O4 shows partial Cu2+ → Cu+ reduction and local delamination, identifying the photocathode as the lifetime-limiting component.
SN - 2079-4991
ER -