Electrochemical and photoelectrochemical characterization of CuFeO2 single crystal

Omeiri, S.; Bellal, B.; Bouguelia, A.; Bessekhouad, Y.; Trari, M.

doi:10.1007/s10008-008-0703-3

Cited by 57 publications

(35 citation statements)

References 22 publications

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“…When combining the 5.2 eV CuFeO 2 work function with the value of 0.2 eV for E F – E VBM , an ionization potential of 5.4 eV is retrieved for the 2H CuFeO 2 pellet. Indeed, Omeiri et al determined through Mott–Schottky flat band measurements that the ionization potential of the (001) surface of a 3R CuFeO 2 single crystal amounts to 5.4 eV . Due to the Mott–Schottky measurements being performed at the point of zero charge, the similarity of the CuFeO 2 surfaces and the similarity of the ionization potentials, the presence of a strong surface dipole at the 2H CuFeO 2 pellet surface is regarded as being unlikely.…”

Section: Resultsmentioning

confidence: 99%

“…Because 2H CuFeO 2 cannot be easily synthesized, only 3R CuFeO 2 has been studied extensively so far. The suitability of 3R CuFeO 2 for water reduction stems from its appropriate properties such as its reduced bandgap of 1.5 eV, its suitable conduction band minimum, which allows for water reduction, its good carrier mobility of about 0.2 cm 2 V −1 s −1 , and because it is composed of earth‐abundant elements.…”

Section: Introductionmentioning

confidence: 99%

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Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Hermans

Klein

Sarker

et al. 2020

Adv Funct Materials

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CuFeO2 is recognized as a potential photocathode for photo(electro)chemical water splitting. However, photocurrents with CuFeO2‐based systems are rather low so far. In order to optimize charge carrier separation and water reduction kinetics, defined CuFeO2/Pt, CuFeO2/Ag, and CuFeO2/NiOx(OH)y heterostructures are made in this work through a photodeposition procedure based on a 2H CuFeO2 hexagonal nanoplatelet shaped powder. However, water splitting performance tests in a closed batch photoreactor show that these heterostructured powders exhibit limited water reduction efficiencies. To test whether Fermi level pinning intrinsically limits the water reduction capacity of CuFeO2, the Fermi level tunability in CuFeO2 is evaluated by creating CuFeO2/ITO and CuFeO2/H2O interfaces and analyzing the electronic and chemical properties of the interfaces through photoelectron spectroscopy. The results indicate that Fermi level pinning at the Fe3+/Fe2+ electron polaron formation level may intrinsically prohibit CuFeO2 from acquiring enough photovoltage to reach the water reduction potential. This result is complemented with density functional theory calculations as well.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Hermans

Klein

Sarker

et al. 2020

Adv Funct Materials

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“…Despite the repeated findings of poor conductivity compared to their n-type TCO counterparts, CuM III O 2 TCOs retain popularity as a viable platform for future high performance p-type TCO applications. 79,80 In addition, delafossite structured materials have started to receive attention as potential electrodes in photoelectrochemical ͑PEC͒ water splitting, 65,[81][82][83][84][85][86][87][88] in spite of the fact that in many cases their band gaps are far in excess of the required range for PEC applications ͑1.7-2.2 eV͒. 89 It is clear from our results that due to the polaronic nature of these Cu I oxides, 69,70,90 effective mass theory is not an ideal way to rank the conductivity properties of delafossite materials.…”

Section: Discussionmentioning

confidence: 99%

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Scanlon

Godinho²,

Morgan³

et al. 2010

The Journal of Chemical Physics

107

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The Cu I -based delafossite structure, Cu I M III O 2 , can accommodate a wide range of rare earth and transition metal cations on the M III site. Substitutional doping of divalent ions for these trivalent metals is known to produce higher p-type conductivity than that occurring in the undoped materials. However, an explanation of the conductivity anomalies observed in these p-type materials, as the trivalent metal is varied, is still lacking. In this article, we examine the electronic structure of Cu I M III O 2 ͑M III =Al,Cr,Sc,Y͒ using density functional theory corrected for on-site Coulomb interactions in strongly correlated systems ͑GGA+ U͒ and discuss the unusual experimental trends. The importance of covalent interactions between the M III cation and oxygen for improving conductivity in the delafossite structure is highlighted, with the covalency trends found to perfectly match the conductivity trends. We also show that calculating the natural band offsets and the effective masses of the valence band maxima is not an ideal method to classify the conduction properties of these ternary materials.

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“…The turn-on voltage and reverse leakage current values are found to be 0.9 V and 4 μA at −2 V. Figure 6 shows the energy band diagram of the junction. The electron affinity and bandgap values for CFO and n-Si are χ CFO = 4.21 eV [21], E g CFO = 3.25 eV and χ Si = 4.05 eV, E g Si = 1.12 eV [22], respectively. The model shows a small conduction band offset (0.16 eV) and a large valence band offset (2.29 eV).…”

Section: Resultsmentioning

confidence: 99%

Room temperature deposition of amorphous p-type CuFeO2 and fabrication of CuFeO2/n-Si heterojunction by RF sputtering method

et al. 2016

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Transparent conducting amorphous p-type CuFeO 2 (CFO) thin film was prepared by radio-frequency (RF) magnetron sputtering method at room temperature using polycrystalline CuFeO 2 target. Amorphous structure of as-deposited film was confirmed by XRD. XPS analysis convinced that the chemical state of Cu + and Fe 3+ in the film, and the chemical composition of the thin films is close to the stoichiometry of CuFeO 2 . Surface morphology of the film was analysed by SEM studies. p-type nature and concentration of carriers was investigated by Hall effect measurement. The p-n heterojunction in the structure of Al/n-Si/p-CuFeO 2 /Al showed good rectifying behaviour with a forward and reverse currents ratio of 555 at 2 V. The turn-on voltage and reverse leakage current values were found to be 0.9 V and 4 μA at −2 V. Further, the conduction mechanism of forward bias voltage was controlled by thermionic emission (TE) and trap-space charge limited current (TCLC) mechanisms.

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Electrochemical and photoelectrochemical characterization of CuFeO2 single crystal

Cited by 57 publications

References 22 publications

Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Room temperature deposition of amorphous p-type CuFeO2 and fabrication of CuFeO2/n-Si heterojunction by RF sputtering method

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Electrochemical and photoelectrochemical characterization of CuFeO2 single crystal

Cited by 57 publications

References 22 publications

Pinning of the Fermi Level in CuFeO2 by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Pinning of the Fermi Level in CuFeO2 by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Understanding conductivity anomalies in CuI-based delafossite transparent conducting oxides: Theoretical insights

Room temperature deposition of amorphous p-type CuFeO2 and fabrication of CuFeO2/n-Si heterojunction by RF sputtering method

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Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting