Strategies for the deposition of LaFeO<sub>3</sub> photocathodes: improving the photocurrent with a polymer template

Freeman, Emma; Kumar, Santosh; Celorrio, Verónica; Park, Min Su; Kim, Jong Hak; Fermı́n, David J.; Eslava, Salvador

doi:10.1039/c9se01103j

Cited by 18 publications

(16 citation statements)

References 58 publications

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“…[139] The photoelectrodes exhibited low photocurrents in an N 2 -purged electrolyte, which dramatically increased in the presence of O 2 as an electron scavenger. A similar behavior was observed by Liu et al [144] and Freeman et al [145] using different synthetic methods, not only for LaFeO 3 , but also for NbFeO 3 thin films. [142] The need for modification of the material in order to overcome the sluggish charge transfer to water is apparent.…”

Section: Perovskitessupporting

confidence: 87%

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Díez‐García

Gómez

2022

Solar RRL

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The conversion of solar energy into fuels and, specifically hydrogen, is a critical process for ensuring the sustainability of the future energy system. Among the different ways of converting solar energy into fuels and chemicals, photoelectrochemical tandem cells, containing two photoactive materials, stand out as they have the potential for direct solar‐to‐fuel conversion, thus minimizing cost. The implementation of photoelectrolysis for hydrogen generation is hindered by the lack of suitable electrode materials, particularly photocathodes. Among the candidates for photocathodes, ternary (and multinary) transition metal oxides have the advantage of lower cost and, potentially, higher stability than other metal compounds. Herein, the aim is to provide an overview of the current state of the art for ternary oxides (spinels, delafossites, perovskites, etc.), with a focus on the modification strategies that can optimize their behavior and applicability. Both copper‐based and iron‐based ternary oxides are the most studied and, currently, the most promising. Among the strategies being used for their optimization, doping, the deposition of underlayers and overlayers, and the use of cocatalysts are the most popular. However, it is apparent that both solar‐to‐hydrogen efficiencies and stability will need to be addressed in the future. Some guidelines in this respect are also provided.

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Section: Perovskitessupporting

confidence: 87%

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Díez‐García

Gómez

2022

Solar RRL

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“…LaFeO 3 (LFO) is a p-type semiconductor exhibiting high photovoltages toward the HER, but low EQE values, regardless of the synthesis methods. − ,, In a recent publication, we identify that EQE can be substantially enhanced by depositing a thin TiO 2 film, which acts as a hole-blocking layer at the LFO/water interface . EQE enhancement has also been reported by depositing a thin Au interlayer between the FTO and LFO films .…”

Section: Introductionmentioning

confidence: 99%

Promoting Active Electronic States in LaFeO₃ Thin-Films Photocathodes via Alkaline-Earth Metal Substitution

Sun

Fermı́n

2020

ACS Appl. Mater. Interfaces

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The effects of alkaline-earth metal cation (AMC: Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ ) substitution on the photoelectrochemical properties of phase-pure LaFeO3 (LFO) thin-films are elucidated by X-ray Photoemission Spectroscopy (XPS), X-ray Diffraction (XRD), diffuse reflectance and electrochemical impedance spectroscopy (EIS). XRD confirms the formation of single-phase cubic LFO thin films, with a rather complex dependence on the nature of the AMC and extent of substitution. Interestingly, subtle trends in lattice constant variations observed in XRD are closely correlated with shifts in the binding energies of Fe 2p3/2 and O 1s orbitals associated with the perovskite lattice. We establish a scaling factor between these two photoemission peaks, unveiling key correlation between Fe oxidation state and Fe-O covalency. Diffuse reflectance shows that optical transitions are little affected by AMC substitution below 10%, which are dominated by a direct bandgap transition close to 2.72 eV. Differential capacitance data obtained from EIS confirm the p-type characteristic of pristine LFO thin-films, revealing the presence of sub-bandgap electronic state (A-states) close to the valence band edge. The density of A-states is decreased upon AMC substitution, while the overall capacitance increases (increase in dopant level) and the apparent flat-band potential shifts towards more positive potentials. This behaviour is consistent with the change in the valence band photoemission edge. In addition, capacitance data of cation-substituted films show the emergence of deeper states centred around 0.6 eV above the valence band edge (B-states). Photoelectrochemical responses towards the hydrogen evolution and oxygen reduction reactions in alkaline solutions show a complex dependence on alkaline-earth metal incorporation, reaching incident-photon-to-current conversion efficiency close to 20% in oxygen saturated solutions. We rationalise the photoresponses of the LFO films in terms of the effect sub-bandgap states on majority carrier mobility, charge transfer and recombination kinetics.

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“…Additional benefits include abundant starting materials and high levels of structural flexibility . In a previous article, we have reviewed the use of different perovskite oxides for photocatalytic and PEC applications . Many required the use of metal doping to allow for a reduction of band gap to assist in visible light absorption, such as in the cases of Bi‐NaTaO 3 and Rh‐SrTiO 3 that have both shown activity for water reduction .…”

Section: Introductionmentioning

confidence: 99%

“…[27,28] LaFeO 3 (LFO) has also shown p‐type behavior with an ideal band gap of ∼2.1 eV and has shown to be active in dye degradation, oxygen reduction and water reduction . Photocurrents for bare LFO have reached around −160 μA cm −2 at +0.26 V RHE using a spray pyrolysis synthesis method or −161 μA cm −2 at +0.43 V RHE using a polymer templating method . An electrodeposited film achieved −124 μA cm −2 for bare LFO, which increased to −268 μA cm −2 at +0.6 V RHE on K‐doping in O 2 purged electrolyte .…”

Section: Introductionmentioning

confidence: 99%

PrFeO₃ Photocathodes Prepared Through Spray Pyrolysis

et al. 2020

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Perovskite oxides are receiving wide interest for photocatalytic and photoelectrochemical devices, owing to their suitable band gaps for solar light absorption and stability in aqueous applications. Herein, we assess the activity of PrFeO3 photocathodes prepared by using spray pyrolysis and calcination temperatures between 500 and 700 °C. Scanning electron microscopy shows corrugated films of high surface coverage on the conductive glass substrate. The electrochemically active surface area shows slight decreases with temperature increases from 500 to 600 and 700 °C. However, transient photocurrent responses and impedance spectroscopy data showed that films calcined at higher temperatures reduced the probabilities of recombination due to trap states, resulting in faster rates of charge extraction. In this trade‐off, a calcination temperature of 600 °C provided a maximum photocurrent of ‐130±4 μA cm−2 at +0.43 VRHE under simulated sunlight, with an incident photon‐to‐current conversion efficiency of 6.6 % at +0.61 VRHE and 350 nm and an onset potential of +1.4 VRHE for cathodic photocurrent.

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Strategies for the deposition of LaFeO₃ photocathodes: improving the photocurrent with a polymer template

Abstract: LaFeO3 photocathodes with high porosity and uniformity are developed through polymer templating with Triton X-100, improving charge separation and boosting photocurrents achieved.

Cited by 18 publications

References 58 publications

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Promoting Active Electronic States in LaFeO₃ Thin-Films Photocathodes via Alkaline-Earth Metal Substitution

PrFeO₃ Photocathodes Prepared Through Spray Pyrolysis

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Strategies for the deposition of LaFeO3 photocathodes: improving the photocurrent with a polymer template

Abstract: LaFeO3 photocathodes with high porosity and uniformity are developed through polymer templating with Triton X-100, improving charge separation and boosting photocurrents achieved.

Cited by 18 publications

References 58 publications

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Progress in Ternary Metal Oxides as Photocathodes for Water Splitting Cells: Optimization Strategies

Promoting Active Electronic States in LaFeO3 Thin-Films Photocathodes via Alkaline-Earth Metal Substitution

PrFeO3 Photocathodes Prepared Through Spray Pyrolysis

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Product

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Strategies for the deposition of LaFeO₃ photocathodes: improving the photocurrent with a polymer template

Promoting Active Electronic States in LaFeO₃ Thin-Films Photocathodes via Alkaline-Earth Metal Substitution

PrFeO₃ Photocathodes Prepared Through Spray Pyrolysis