Design of Semiconducting Tetrahedral<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Mn</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Zn</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">O</mml:mi></mml:mrow></mml:math>Alloys and Their Application to Solar Water Splitting

Peng, Haowei; Ndione, Paul F.; Ginley, David S.; Zakutayev, Andriy; Lany, Stephan

doi:10.1103/physrevx.5.021016

Cited by 51 publications

(87 citation statements)

References 63 publications

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“…The energy difference between the final and initial states defines the self-trapping energy EST for the small polaron, and a negative EST means a stable small-polaron state. The small polaron is a special kind of point defect and can be explored with the wellestablished generalized Koopmans' condition (GKC) approach (20)(21)(22)(23).…”

Section: Resultsmentioning

confidence: 99%

Redox properties of birnessite from a defect perspective

Peng

McKendry

Ding

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Birnessite, a layered-structure MnO 2 , is an earth-abundant functional material with potential for various energy and environmental applications, such as water oxidation. An important feature of birnessite is the existence of Mn(III) within the MnO 2 layers, accompanied by interlayer charge-neutralizing cations. Using first-principles calculations, we reveal the nature of Mn(III) in birnessite with the concept of the small polaron, a special kind of point defect. Further taking into account the effect of the spatial distribution of Mn(III), we propose a theoretical model to explain the structure-performance dependence of birnessite as an oxygen evolution catalyst. We find an internal potential step which leads to the easy switching of the oxidation state between Mn(III) and Mn(IV) that is critical for enhancing the catalytic activity of birnessite. Finally, we conduct a series of comparative experiments which support our model.birnessite MnO 2 | small polaron | catalysis | water oxidation P hotoelectrochemical (PEC) splitting of water into H2 and O2 (artificial photosynthesis) provides an attractive way to harvest solar energy. The process consists of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), both of which are facilitated with catalysts in practice. Currently, one of the biggest challenges is to develop a cheap and efficient catalyst for the former reaction with a low overpotential, which is still needed to overcome the kinetic barriers (already lowered by the catalyst) along the path from reactants to products. Birnessite, similar to the oxygen-evolving complex in Photosystem II for photosynthesis in regard to the coexistence of Mn(III) (nominal Mn 3+ ) and Mn(IV) (nominal Mn 4+ ) within its structure (1-3), has already shown a moderate catalytic performance with the overpotentials reported from 0.6 V to 0.8 V (4-8).Birnessite has the general formula Mx MnO2·1.5(H2O), composed of layers of edge-sharing MnO6 octahedra as shown in Fig. 1 for the hexagonal phase, and an interlayer of randomly distributed water molecules and metal (M) cations (like K + , Na + , and Ca 2+ ). With the charge balanced by the interlayer cations, some of the Mn cations within the MnO2 layer are reduced from Mn(IV) to Mn(III). The coexistence of Mn(IV) and Mn(III), and further the "balanced equilibrium" or low energy barrier between them, has been suspected to be a critical factor for its catalytic activity (1). The importance of the high-spin Mn(III), through its e 1 g electronic configuration, has been realized in other manganese oxides for OER catalysis (2, 9) and also follows the design principle of Suntivich et al. (10) that a near-unity eg occupancy may imply good OER catalytic activity. This easy switching of the oxidation state is also a typical behavior for the transition metal cation undergoing back and forth changes between several oxidation states in OER catalysts during the water oxidation cycle (11-13). OER catalysts like Co-and Ni-doped hematite (12) and cobalt oxides (13), as well as ...

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Section: Resultsmentioning

confidence: 99%

Redox properties of birnessite from a defect perspective

Peng

McKendry

Ding

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

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“…Such calculations, however, are for the moment rather far from routine. The same holds for calculations that aim to model the mobility of free charge carriers [137][138][139][140][141][142][143], which is a crucial property for good photoelectrodes but less relevant for polymeric and nanoparticulate systems where exciton dissociation occurs on the surface, and for calculations that explicitly study the electron/hole transfer between different sub-components of the photocatalyst and the photocatalyst and solution/surface species [99,144].…”

Section: Exciton Dissociation and Electron-hole Separationmentioning

confidence: 99%

Modelling materials for solar fuel synthesis by artificial photosynthesis; predicting the optical, electronic and redox properties of photocatalysts

Guiglion

Berardo

Butchosa

et al. 2016

J. Phys.: Condens. Matter

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In this mini-review, we discuss what insight computational modelling can provide into the working of photocatalysts for solar fuel synthesis and how calculations can be used to screen for new promising materials for photocatalytic water splitting and carbon dioxide reduction. We will extensively discuss the different relevant (material) properties and the computational approaches (DFT, TD-DFT, GW/BSE) available to model them. We illustrate this with examples from the literature, focussing on polymeric and nanoparticle photocatalysts. We finish with a perspective on the outstanding conceptual and computational challenges.

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“…194 Similarly, MnO has been described as the tetrahedral wurtzite structure instead of the octahedral rock-salt. 195 These shortcomings have recently been addressed using the computationally-intensive calculations in the random phase approximation (RPA), 196,197 which yield the correct ground-state for MnO 56,198 and TiO 2 . 193 …”

Section: Crystal Structurementioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

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ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

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Design of Semiconducting TetrahedralMn1−xZnxOAlloys and Their Application to Solar Water Splitting

Cited by 51 publications

References 63 publications

Redox properties of birnessite from a defect perspective

Redox properties of birnessite from a defect perspective

Modelling materials for solar fuel synthesis by artificial photosynthesis; predicting the optical, electronic and redox properties of photocatalysts

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

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