scholarly journals Ligand size effects in two-dimensional hybrid copper halide perovskites crystals

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Arramel Arramel ◽  
Angga Dito Fauzi ◽  
Xinmao Yin ◽  
Chi Sin Tang ◽  
Muhammad Haris Mahyuddin ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Electronic Systems ◽  
Two Dimensional ◽  
Copper Halide ◽  
Functional Theory ◽  
Optical Responses ◽  
Halide Perovskites ◽  
The Impact ◽  
X Ray Absorption

AbstractIntensive effort to tailor photophysics of lead-free perovskites is appealing in recent years. However, their combined electronic and optical property elucidations remain elusive. Here, we report spectroscopic observations of the coexistence Zhang-Rice singlet state and exotic electronic transitions in two-dimensional copper-based perovskites. Herein, several perovskites with different alkylammonium spacers are investigated to unravel their correlated electronic systems and optical responses. Namely, methylammonium, ethylammonium, phenylmethylammonium and phenethylammonium. Using temperature dependent high-resolution X-ray absorption spectroscopy, we observe distinct electronic features highlighting the impact of short spacer chains compared to long-conjugated ligands, demonstrating a pronounced 3d9 and 3d9L signature linewidth variation. Corroborated by density functional theory calculations, the transient dynamics evolution of copper-based hybrid perovskites is influenced by the strong interplay of electron-phonon interactions and geometric constrictions. This finding sheds light on tuning the electronic and optical properties of hybrid perovskites towards efficient photoactive-based devices.

scholarly journals Exposing unsaturated Cu1-O2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution

2021 ◽  
Vol 7 (18) ◽  
pp. eabg2580
Author(s):  
Weiren Cheng ◽  
Huabin Zhang ◽  
Deyan Luan ◽  
Xiong Wen (David) Lou
Keyword(s):  
Hydrogen Evolution ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Active Centers ◽  
Functional Theory ◽  
Hollow Nanostructure ◽  
Metal Organic ◽  
X Ray Absorption ◽  
A Current

Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics.

scholarly journals Nanoribbons with Non-Alternant Topology from Fusion of Polyazulene: Carbon Allotropes Beyond Graphene

2019 ◽  
Author(s):  
Qitang Fan ◽  
Daniel Martin-Jimenez ◽  
Daniel Ebeling ◽  
Claudio K. Krug ◽  
Lea Brechmann ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Low Temperature ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Scanning Probe ◽  
Two Dimensional ◽  
Reaction Step ◽  
Functional Theory ◽  
Carbon Allotropes ◽  
Temperature Scanning

Various two-dimensional (2D) carbon allotropes with non-alternant topologies, such as pentaheptites and phagraphene, have been proposed. Predictions indicate that these metastable carbon polymorphs, which contain odd-numbered rings, possess unusual (opto)electronic properties. However, none of these materials has been achieved experimentally due to synthetic challenges. In this work, by using on-surface synthesis, nanoribbons of the non-alternant graphene allotropes, phagraphene and tetra-penta-hepta(TPH)-graphene have been obtained by dehydrogenative C-C coupling of 2,6-polyazulene chains. These chains were formed in a preceding reaction step via on-surface Ullmann coupling of 2,6-dibromoazulene. Low-temperature scanning probe microscopies with CO-functionalized tip and density functional theory calculations have been used to elucidate their structural properties. <br>

scholarly journals Mechanochemical Synthesis of a Mercury(II) Metal-Organic Framework Reveals a Two-Dimensional Polymorph Stabilized by Weak Interactions

2019 ◽  
Author(s):  
Isaiah R. Speight ◽  
Igor Huskić ◽  
Mihails Arhangelskis ◽  
Hatem M. Titi ◽  
Robin Stein ◽  
...  
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Density Functional Theory Calculations ◽  
Dimensional Structure ◽  
Reaction Monitoring ◽  
Two Dimensional ◽  
Functional Theory ◽  
Metal Organic

Solid-state mechanochemistry revealed a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional structure, with the unexpected stabilization of a lower dimensionality structure explained by contributions of weak interactions, which include short C-H···Hg contacts.

Two-dimensional metal-organic frameworks Mo3(C2O)12 as promising single-atom catalysts for selective nitrogen-to-ammonia

2022 ◽  
Author(s):  
Zhen Feng ◽  
Zelin Yang ◽  
Xiaowen Meng ◽  
Fachuang Li ◽  
Zhanyong Guo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Metal Organic Frameworks ◽  
Density Functional Theory Calculations ◽  
Reduction Reaction ◽  
Single Atom ◽  
Two Dimensional ◽  
Functional Theory ◽  
New Family ◽  
Metal Organic

The development of single-atom catalysts (SACs) for electrocatalytic nitrogen reduction reaction (NRR) remains a great challenge. Using density functional theory calculations, we design a new family of two-dimensional metal-organic frameworks...

scholarly journals Two-dimensional Dirac fermions on oxidized black phosphorus

2019 ◽  
Vol 21 (43) ◽  
pp. 24206-24211
Author(s):  
Seoung-Hun Kang ◽  
Jejune Park ◽  
Sungjong Woo ◽  
Young-Kyun Kwon
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Black Phosphorus ◽  
Inversion Symmetry ◽  
Dirac Fermions ◽  
Two Dimensional ◽  
Functional Theory

Using ab initio density functional theory calculations, we find four-fold degenerate Dirac points protected by two nonsymmorphic symmetries in phosphorene oxide with the inversion symmetry broken.

Two dimensional MoS2 meets porphyrins via intercalation to enhance the electrocatalytic activity toward hydrogen evolution

Nanoscale ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 3780-3785 ◽  
Author(s):  
Ik Seon Kwon ◽  
In Hye Kwak ◽  
Hafiz Ghulam Abbas ◽  
Hee Won Seo ◽  
Jaemin Seo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Electrocatalytic Activity ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Two Dimensional ◽  
Functional Theory ◽  
Spin Polarized

Mn-Porphyrin-MoS2 exhibits excellent electrocatalytic activity toward the hydrogen evolution reaction, which is supported by spin-polarized density functional theory calculations.

scholarly journals A First-Principles Exploration of NaxSy Binary Phases at 1 atm and Under Pressure

Crystals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 441 ◽  
Author(s):  
Nisha Geng ◽  
Tiange Bi ◽  
Niloofar Zarifi ◽  
Yan Yan ◽  
Eva Zurek
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elemental Sulfur ◽  
Density Functional Theory Calculations ◽  
Metastable Phases ◽  
Van Der Waals Interactions ◽  
Two Dimensional ◽  
Functional Theory ◽  
Battery Materials

Interest in Na-S compounds stems from their use in battery materials at 1 atm, as well as the potential for superconductivity under pressure. Evolutionary structure searches coupled with Density Functional Theory calculations were employed to predict stable and low-lying metastable phases of sodium poor and sodium rich sulfides at 1 atm and within 100–200 GPa. At ambient pressures, four new stable or metastable phases with unbranched sulfur motifs were predicted: Na2S3 with C 2 / c and Imm2 symmetry, C 2 -Na2S5 and C 2 -Na2S8. Van der Waals interactions were shown to affect the energy ordering of various polymorphs. At high pressure, several novel phases that contained a wide variety of zero-, one-, and two-dimensional sulfur motifs were predicted, and their electronic structures and bonding were analyzed. At 200 GPa, P 4 / m m m -Na2S8 was predicted to become superconducting below 15.5 K, which is close to results previously obtained for the β -Po phase of elemental sulfur. The structures of the most stable M3S and M4S, M = Na, phases differed from those previously reported for compounds with M = H, Li, K.

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