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Revealing the relationship between photoelectrochemical performance and interface hole trapping in CuBi₂O₄ heterojunction photoelectrodes.

ABSTRACT: p-Type CuBi₂O₄ is considered a promising metal oxide semiconductor for large-scale, economic solar water splitting due to the optimal band structure and low-cost fabrication. The main challenge in utilizing CuBi₂O₄ as a photoelectrode for water splitting, is that it must be protected from photo-corrosion in aqueous solutions, an inherent problem for Cu-based metal oxide photoelectrodes. In this work, several buffer layers (CdS, BiVO₄, and Ga₂O₃) were tested between CuBi₂O₄ and conformal TiO₂ as the protection layer. RuO _x was used as the co-catalyst for hydrogen evolution. Factors that limit the photoelectrochemical performance of the CuBi₂O₄/TiO₂/RuO _x , CuBi₂O₄/CdS/TiO₂/RuO _x , CuBi₂O₄/BiVO₄/TiO₂/RuO _x and CuBi₂O₄/Ga₂O₃/TiO₂/RuO _x heterojunction photoelectrodes were revealed by comparing photocurrents, band offsets, and directed charge transfer measured by modulated surface photovoltage spectroscopy. For CuBi₂O₄/Ga₂O₃/TiO₂/RuO _x photoelectrodes, barriers for charge transfer strongly limited the performance. In CuBi₂O₄/CdS/TiO₂/RuO _x , the absence of hole traps resulted in a relatively high photocurrent density and faradaic efficiency for hydrogen evolution despite the presence of pronounced deep defect states at the CuBi₂O₄/CdS interface. Hole trapping limited the performance moderately in CuBi₂O₄/BiVO₄/TiO₂/RuO _x and strongly in CuBi₂O₄/TiO₂/RuO _x photoelectrodes. For the first time, our results show that hole trapping is a key factor that must be addressed to optimize the performance of CuBi₂O₄-based heterojunction photoelectrodes.

SUBMITTER: Song A

PROVIDER: S-EPMC8162275 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:One of the emerging and environmentally friendly technologies is the photoelectrochemical generation of green hydrogen; however, the cheap cost of production and the need for customizing photoelectrode properties are thought to be the main obstacles to the widespread adoption of this technology. The primary players in hydrogen production by photoelectrochemical (PEC) water splitting, which is becoming more common on a worldwide basis, are solar renewable energy and widely available metal oxide based PEC electrodes. This study attempts to prepare nanoparticulate and nanorod-arrayed films to better understand how nanomorphology can impact structural, optical, and PEC hydrogen production efficiency, as well as electrode stability. Chemical bath deposition (CBD) and spray pyrolysis are used to create ZnO nanostructured photoelectrodes. Various characterization methods are used to investigate morphologies, structures, elemental analysis, and optical characteristics. The crystallite size of the wurtzite hexagonal nanorod arrayed film was 100.8 nm for the (002) orientation, while the crystallite size of nanoparticulate ZnO was 42.1 nm for the favored (101) orientation. The lowest dislocation values for (101) nanoparticulate orientation and (002) nanorod orientation are 5.6 × 10-4 and 1.0 × 10-4 dislocation/nm2, respectively. By changing the surface morphology from nanoparticulate to hexagonal nanorod arrangement, the band gap is decreased to 2.99 eV. Under white and monochromatic light irradiation, the PEC generation of H2 is investigated using the proposed photoelectrodes. The solar-to-hydrogen conversion rate of ZnO nanorod-arrayed electrodes was 3.72% and 3.12%, respectively, under 390 and 405 nm monochromatic light, which is higher than previously reported values for other ZnO nanostructures. The output H2 generation rates for white light and 390 nm monochromatic illuminations were 28.43 and 26.11 mmol.h-1cm-2, respectively. The nanorod-arrayed photoelectrode retains 96.6% of its original photocurrent after 10 reusability cycles, compared to 87.4% for the nanoparticulate ZnO photoelectrode. The computation of conversion efficiencies, H2 output rates, Tafel slope, and corrosion current, as well as the application of low-cost design methods for the photoelectrodes, show how the nanorod-arrayed morphology offers low-cost, high-quality PEC performance and durability.

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Revealing the relationship between photoelectrochemical performance and interface hole trapping in CuBi₂O₄ heterojunction photoelectrodes.

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Revealing the relationship between photoelectrochemical performance and interface hole trapping in CuBi₂O₄ heterojunction photoelectrodes.