Flat-Band Potential Techniques

Chen, Zhebo; Deutsch, Todd G.; Dinh, Huyen N.; Domen, Kazunari; Emery, K.; Forman, Arnold J.; Gaillard, Nicolas; Garland, Roxanne; Heske, Clemens; Jaramillo, Thomas F.; Kleiman‐Shwarsctein, Alan; Miller, Eric L.; Takanabe, Kazuhiro; Turner, John A.

doi:10.1007/978-1-4614-8298-7_6

Cited by 18 publications

(22 citation statements)

References 18 publications

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“…This photocorrosion directly results in slow and fast drifts of the measured potentials over the test course of about 60 s for BBNO-2 (Figure c,d) and BBO electrode (Figure e), respectively; meanwhile, it additionally accounts for the significant overall shifts in chopped OCPs between the test circles under different illumination intensities (see panels c–e of Figure ). All of our BBO electrodes suffer from severe photocorrosions during the illuminated OCP tests (Figure S7b); as a result, some of them did not exhibit very obvious ΔOCP when turn the light on and off (Figure S6f). Besides, BBNO-1 samples do not exhibit significant photocorrosion during the illuminated OCP tests, because we observed neither considerable color film changes after OCP tests with various light intensities nor the drifts/shifts of the measured potentials over the entire test courses (Figure a,b).…”

Section: Resultsmentioning

confidence: 99%

“…Besides, BBNO-1 samples do not exhibit significant photocorrosion during the illuminated OCP tests, because we observed neither considerable color film changes after OCP tests with various light intensities nor the drifts/shifts of the measured potentials over the entire test courses (Figure a,b). But, these two wide-bandgap BBNO-1 electrodes demonstrate very slow ΔOCP responses upon turning the light on and off (Figure a,b), compared to the two low-bandgap BBNO-2 electrodes (Figure c,d), indicating that BBNO-2 electrodes with smaller bandgaps and better electrical properties possess better material qualities for PEC applications . In principle, illuminated OCP technique can additionally be used to estimate the E FB as long as the above-bandgap illumination is sufficiently intense to completely flatten the band bending and that the materials do not experience severe Fermi lever pinning at the electrode–electrolyte interface .…”

Section: Resultsmentioning

confidence: 99%

“…Thus, p-type electrode materials will show a positive shift in OCP upon illumination; instead, n-type semiconductors will exhibit a negative shift in illuminated OCP. 51,52 Figure 8 shows the measured OCPs of our synthesized BBNO electrodes under chopped illumination with various light intensities, where the positive shift in OCP upon illumination indicates that our synthesized BBNO alloy films show the ptype conductivity. We tested about 80 pieces of BBNO electrodes with various compositions and all the OCP tests confirm that our synthesized BBNO based semiconductors process the p-type conductivity even for the samples for which MS plots fail to determine.…”

Section: Chemistry Of Materialsmentioning

confidence: 99%

“…But, these two wide-bandgap BBNO-1 electrodes demonstrate very slow ΔOCP responses upon turning the light on and off (Figure 8a,b), compared to the two low-bandgap BBNO-2 electrodes (Figure 8c,d), indicating that BBNO-2 electrodes with smaller bandgaps and better electrical properties possess better material qualities for PEC applications. 52 In principle, illuminated OCP technique can additionally be used to estimate the E FB as long as the above-bandgap illumination is sufficiently intense to completely flatten the band bending and that the materials do not experience severe Fermi lever pinning at the electrode−electrolyte interface. 51 The reduce of the ΔOCP over illumination intensity suggests that the AM 1.5G with a 100 mW•cm −2 irradiation intensity seems not sufficiently intense to saturate OCP.…”

Section: Chemistry Of Materialsmentioning

confidence: 99%

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Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Yin

Yan

2018

Chem. Mater.

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Photoelectrochemical (PEC) water reduction is a long-term strategical technology for hydrogen production. In this work, we synthesize a series of compact and nano/mesoporous Nb-substituted BaBiO3 [i.e., Ba2Bi(Bi1–x Nb x )O6, 0 ≤ x ≤ 0.93, BBNO] thin films using cost-effective chemical solution methods. The synthesized BBNO alloy based thin films demonstrate tunable bandgaps from 1.41 eV (x = 0) to 1.89 eV (x = 0.93) to efficiently absorb the solar spectrum and p-type conductivities suitable for hydrogen production. The photoelectrodes with a configuration fluorine-doped SnO2/BBNO (0 ≤ x ≤ 0.93)/Pt produce cathodic photocurrents of 0.05–1 mA·cm–2 at 0 VRHE (volt versus reversible hydrogen electrode) measured in a neutral (pH = 7.2) phosphate buffer and under simulated AM 1.5G illumination (100 mW·cm–2). The BaBiO3 without Nb alloying based electrode delivers the best photocurrent of 1 mA·cm–2 at 0 VRHE but is subjected to severe corrosions during the PEC related tests. Alloying Nb has an obvious influence on enhancing the material stability against corrosion. With Nb alloying, the screen-printed nanoporous BBNO (x = 0.6, bandgap = 1.62 eV) based photoelectrode generates a better photocurrent of 0.2 mA·cm–2 at 0 VRHE with a highly positive onset at 1.5 VRHE enabling unbiased water reduction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Chemistry Of Materialsmentioning

confidence: 99%

Section: Chemistry Of Materialsmentioning

confidence: 99%

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Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Yin

Yan

2018

Chem. Mater.

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“…The shift in Fermi level can be detected as from a shift in the flat-band potential measured from Mott-Schottky (M-S) plots or from illuminated open-circuit voltage measurements. [113] Fermi level equilibration can result in reduced surface charge carrier recombination that can be measured in general from chronoamperometry experiments (J-t) [114] and an onset potential shift for photocurrent that can lead to improved device efficiencies. In addition, plasmonic NPs can be used as electron relays between layers within semiconductor heterostructures.…”

Section: Non-plasmonic Effects For Enhancing Photoelectrochemical Celmentioning

confidence: 99%

Modulation of Semiconductor Photoconversion with Surface Modification and Plasmon

Bright¹

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Semiconductor devices are the basis of modern technology. Semiconductor-based photoconversion devices that convert light into electrical signals have shown potential for light energy harvesting and conversion, environmental remediation, and sensors for detection of light, chemicals, and biological substances. Despite this potential for use in many applications, semiconductor photoconversion devices need further improvement in the photoconversion performance. This photoconversion improvement may be manifested as increased photoconversion efficiencies for light harvesting devices for power generation such as photovoltaics and photoelectrochemical (PEC) cells or improved photoconversion modulation to increase the sensitivity of semiconductor photoconversion-based sensors. In addition, alternative semiconductor materials to semiconductors that utilize toxic heavy metals such as cadmium and lead must be found for use in certain semiconductor photoconversion devices. In this dissertation, three separate projects related to improving the performance of semiconductor photoconversion devices are presented. In the first project presented, a rutile titanium dioxide (TiO2) nanorod array photoanrode is coated with an ultra-thin porphyrin-based metal-organic framework (MOF) layer to improve the overall photoconversion of the photoelectrode for solar water splitting. The porphyrin-based MOF coated TiO2 nanorod array showed a 2.7x increase in photocurrent versus bare TiO2 nanorod arrays. The porphyrin-based MOF layer suppressed surface states on the rutile TiO2 nanorod array and increased charge separation and extraction from the rutile TiO2 due to the built-in electric field formed by a depleted p-n junction between the porphyrin-based MOF layer and the rutile TiO2 nanorods. In the second project presented, different plasmonic (hot electron injection and plasmoninduced resonant energy transfer (PIRET)) and non-plasmonic photoconversion enhancement mechanisms were tested for modulating photocurrent in PEC-based sensors using Bi3FeMo2O12 (BFMO) thin film semiconductor photoelectrodes and Hg 2+ as a proof-of-concept analyte for detection. The possible plasmonic and non-plasmonic photoconversion enhancement mechanisms were controlled by choice of conjugated plasmonic nanoprobe between Au and Au@SiO2 coreshell nanoparticles with the BFMO. The conjugated Au NPs enhanced the BFMO thin film's PEC performance through a combination of plasmonic hot electron injection, PIRET, Fermi-level equilibration, and a non-plasmonic internal reflection within the BFMO caused by the conjugated Au NPs. The conjugated Au@SiO2 NPs enhanced the BFMO thin film's PEC performance via PIRET and the non-plasmonic internal reflection within the BFMO caused by the Au@SiO2 NPs.

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Strengthening of Titanium by Equal Channel Angular Pressing ‐ Impact on Oxide Layer Properties of Pure Titanium and Ti6Al4V

Franz

Mingler

Krystian

et al. 2020

Adv Materials Inter

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Equal channel angular pressing (ECAP) as a method applicable to large samples for strengthening metallic materials via severe plastic deformation has recently attracted considerable interest. For biomedical applications, ECAP‐treated pure titanium is a promising alternative for implants subjected to high mechanical loads as it contains no potentially cytotoxic alloying elements. The consequences of an ECAP treatment for the physico‐chemical properties of the air formed passive layers of pure or alloyed titanium, which are of the utmost importance for the biological response to these materials, are studied here for the first time. This includes mechanical, electron microscopic, and electrochemical investigations in protein containing media to study the reactions that occur immediately after implantation in the phase boundary between implant and biological system. The ECAP treatment results in a positive shift of the flatband potential and a particularly strong increase of the donor density for the native oxide layers. This is associated with increased electronic conductivity of the oxide layers under anodic polarization.

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Flat-Band Potential Techniques

Cited by 18 publications

References 18 publications

Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Modulation of Semiconductor Photoconversion with Surface Modification and Plasmon

Strengthening of Titanium by Equal Channel Angular Pressing ‐ Impact on Oxide Layer Properties of Pure Titanium and Ti6Al4V

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Flat-Band Potential Techniques

Cited by 18 publications

References 18 publications

Solution-Processed Nb-Substituted BaBiO3 Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Solution-Processed Nb-Substituted BaBiO3 Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Modulation of Semiconductor Photoconversion with Surface Modification and Plasmon

Strengthening of Titanium by Equal Channel Angular Pressing ‐ Impact on Oxide Layer Properties of Pure Titanium and Ti6Al4V

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Product

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Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction

Solution-Processed Nb-Substituted BaBiO₃ Double Perovskite Thin Films for Photoelectrochemical Water Reduction