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1.
Adv Mater ; : e1906015, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-32027058

RESUMO

Developing low-cost, highly efficient, and durable electrocatalysts for oxygen evolution reaction (OER) is essential for the practical application of electrochemical water splitting. Herein, it is discovered that organic small molecule (hexabromobenzene, HBB) can activate commercial transition metal (Ni, Fe, and NiFe) foam by directly evolving metal nanomeshes embedded in graphene-like films (M-NM@G) through a facile Br-induced solid-phase migration process. Systematic investigations indicate that HBB can conformally generate graphene-like network on bulk metal foam substrate via the cleavage of CBr bonds and the formation of CC linkage. Simultaneously, the cleaved CBr fragments can efficiently extract metal atoms from bulk substrate, in situ producing transition metal nanomeshes embedded in the graphene-like films. As a result, such functional nanostructure can serve as an efficient OER electrocatalyst with a low overpotential and excellent long-term stability. Specifically, the overpotential at 100 mA cm-2 is only 208 mV for NiFe-NM@G, ranking the top-tier OER electrocatalysts. This work demonstrates an intriguing general strategy for directly transforming bulk transition metals into nanostructured functional electrocatalysts via the interaction with organic small molecules, opening up opportunities for bridging the application of organic small molecules in energy technologies.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31943656

RESUMO

Nitrogen-doped carbon materials (N-Cmat ) are emerging as low-cost metal-free electrocatalysts for the electrochemical CO2 reduction reaction (CO2 RR), although the activities are still unsatisfactory and the genuine active site is still under debate. We demonstrate that the CO2 RR to CO preferentially takes place on pyridinic N rather than pyrrolic N using phthalocyanine (Pc) and porphyrin with well-defined N-Cmat configurations as molecular model catalysts. Systematic experiments and theoretic calculations further reveal that the CO2 RR performance on pyridinic N can be significantly boosted by electronic modulation from in-situ-generated metallic Co nanoparticles. By introducing Co nanoparticles, Co@Pc/C can achieve a Faradaic efficiency of 84 % and CO current density of 28 mA cm-2 at -0.9 V, which are 18 and 47 times higher than Pc/C without Co, respectively. These findings provide new insights into the CO2 RR on N-Cmat , which may guide the exploration of cost-effective electrocatalysts for efficient CO2 reduction.

3.
Phys Chem Chem Phys ; 22(2): 914-918, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31845940

RESUMO

As a representative in-plane anisotropic two-dimensional (2D) material, germanium monoselenide (GeSe) has attracted considerable attention recently due to its various in-plane anisotropic material properties originating from the low symmetry of a puckered honeycomb structure. Although there have been plenty of reports on the in-plane anisotropic vibrational, electrical and optical properties of GeSe, the strain effect on those appealing anisotropies is still under exploration. Here we report a systematic first-principles computational investigation of strain-engineering of the anisotropic electronic properties of GeSe monolayers. We found that the anisotropic ratio of the effective mass and mobility of charge carriers (electrons and holes) of GeSe along two principle axes can be controlled by using simple strain conditions. Notably, the preferred conducting direction of GeSe can be even rotated by 90° under an appropriate uniaxial strain (>5%). Such effective strain modulation of the electronic anisotropy of GeSe monolayers provides them abundant opportunities for future mechanical-electronic devices.

4.
Small ; 15(49): e1903057, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31701640

RESUMO

Electroless deposition via a spontaneous redox reaction between the metal precursor and support is believed to be a promising approach for the syntheses of supported metal nanoparticles (SMNPs). However, its widespread applications are significantly prohibited by the low reductivity and high cost of support. To overcome these shortcomings, a porous carbon (PC) is herein developed as a promising matrix for the electroless deposition of metal NPs. Benefiting from abundant oxygen-based surface functional groups, the PC shows stronger reducibility (low redox potential) than conventional carbon substrate such as carbon nanotubes or graphene oxide, enabling a facile electroless deposition of Ir, Rh, and Ru NPs on its surface. These SMNPs exhibit an impressive electrocatalytic activity for the hydrogen evolution reaction (HER) or hydrogen oxidation reaction (HOR). For example, the Rh NP/PC can deliver an HER current density of 10 mA cm-2 with a small overpotential of 21 mV in 0.5 m H2 SO4 , while the Ru NP/PC exhibits excellent HOR activity in 0.1 m KOH in terms of high mass and surface specific exchange current density of 263 A g-1 Ru and 0.227 mA cm-2 Ru . The present strategy may open up opportunities for mass production of efficient supported NPs for diverse applications.

5.
Acta Haematol ; : 1-10, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31597158

RESUMO

BACKGROUND: The aim of this study was to detect the expression of long noncoding RNA small nucleolar RNA host gene 18 (SNHG18) andsemaphorin 5A (SEMA5A) genes in multiple myeloma (MM) patients and to explore the correlation of the expression of these genes with the clinical characteristics and prognosis of MM patients. METHODS: Forty-seven newly diagnosed MM, 18 complete remission MM, 13 refractory/relapse MM, and 22 iron deficiency anemia (serving as control) samples were extracted at the Department of Hematology, Second Affiliated Hospital of Xian Jiaotong University between January 2015 and December 2016. The clinical features of the MM patients are summarized. Real-time quantitative PCR was performed to analyze the relative expression levels of the SNHG18 and SEMA5Agenes. The clinical characteristics and overall survival (OS) of the MM patients were statistically analyzed while measuring different levels of SNHG18 and SEMA5Agene expression. At the same time, the correlation between the expression of SNHG18 and SEMA5A was also analyzed. RESULTS: The analysis confirmed that SNHG18 and its possible target gene SEMA5A were both highly expressed in newly diagnosed MM patients. After analyzing the clinical significance of SNHG18 and SEMA5A in MM patients, we found that the expression of SNHG18 and SEMA5A was related to the Durie-Salmon (DS), International Staging System (ISS), and Revised International Staging System (R-ISS) classification systems, and the Mayo Clinic Risk Stratification for Multiple Myeloma (mSMART; p < 0.05). Moreover, we observed a significant difference in OS between the SNHG18/SEMA5A high expression group and the low expression group. We found a positive correlation between SNHG18 and SEMA5A expression (r = 0.709, p < 0.01). Surprisingly, the expected median OS times of both the SNHG18 and SEMA5Ahigh expression groups were significantly decreased, which was in contrast to those of both the SNHG18 and SEMA5Alow expression groups and the single-gene high expression group (p < 0.05). CONCLUSION: High expression of both SNHG18 and SEMA5A is associated with poor prognosis in patients with MM.

6.
J Am Chem Soc ; 141(45): 18075-18082, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31638806

RESUMO

Defect passivation using oxygen has been identified as an efficient and convenient approach to suppress nonradiative recombination and improve the photovoltaic performance of hybrid organic-inorganic halide perovskites (HHPs). However, oxygen can seriously undermine the chemical stability of HHPs due to the reaction of superoxide with protonated organic cations such as CH3NH3+ and [(NH2)2CH]+, thus hindering the deep understanding of how oxygen affects their defect properties. Here we substitute free-proton inorganic Cs+ for organic moiety to avoid the negative effect of oxygen and then systematically investigate the oxygen passivation mechanism in all-inorganic halide perovskites (IHPs) from theory to experiment. We find that, in contrast to conventional oxygen molecule passivation just through physisorption on the surface of perovskites, the oxygen atom can provide a better passivation effect due to its stronger interaction with perovskites. The key point to achieve O-passivated perovskites rather than O2 is the dry-air processing condition, which can dissociate the O2 into O during the annealing process. O-passivated IHP solar cells exhibit enhanced power conversion efficiency (PCE) and better air stability than O2-passivated cells. These results not only provide deep insights into the passivation effect of oxygen on perovskites but also demonstrate the great potential of IHPs for high photovoltaic performance with simplified ambient processing.

7.
ACS Appl Mater Interfaces ; 11(27): 24247-24253, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31246410

RESUMO

In-plane anisotropic two-dimensional (2D) materials, especially black phosphorus and ReS2, have attracted significant interest recently as they can provide one more dimension to manipulate their physical properties when compared with isotropic 2D materials. As a representative anisotropic 2D material, germanium monosulfide (GeS) has emerged as a new research hot topic in this field because of its unique in-plane anisotropic physical properties. Despite the rapid growing progress in the study of GeS, many of their fundamental optical anisotropies are still absent. Here, we report the three-dimensional (3D) optical anisotropy of GeS from theory to experiment. The 3D optical anisotropic properties including extinction, refraction, absorption, and reflection were systematically investigated through density functional calculations. The anisotropic refraction and reflection of GeS were experimentally verified by polarization-resolved optical microscopy and azimuth-dependent reflectance difference microscopy, respectively. Finally, a GeS-based linear dichroic photodetector was demonstrated with a dichroic ratio of 1.45 because of its polarization sensitive absorption. Our results provide deep insights into the optical anisotropy of GeS, which is important for the further development of GeS-based optoelectronic and optical devices.

8.
Angew Chem Int Ed Engl ; 58(28): 9414-9418, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31041835

RESUMO

Interfacial charge collection efficiency has demonstrated significant effects on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Herein, crystalline phase-dependent charge collection is investigated by using rutile and anatase TiO2 electron transport layer (ETL) to fabricate PSCs. The results show that rutile TiO2 ETL enhances the extraction and transportation of electrons to FTO and reduces the recombination, thanks to its better conductivity and improved interface with the CH3 NH3 PbI3 (MAPbI3 ) layer. Moreover, this may be also attributed to the fact that rutile TiO2 has better match with perovskite grains, and less trap density. As a result, comparing with anatase TiO2 ETL, MAPbI3 PSCs with rutile TiO2 ETL delivers significantly enhanced performance with a champion PCE of 20.9 % and a large open circuit voltage (VOC ) of 1.17 V.

9.
Chem Commun (Camb) ; 55(43): 6134, 2019 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-31073586

RESUMO

Correction for 'NiS2 nanodotted carnation-like CoS2 for enhanced electrocatalytic water splitting' by Weili Xin et al., Chem. Commun., 2019, 55, 3781-3784.

10.
ACS Appl Mater Interfaces ; 11(24): 21627-21633, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31136145

RESUMO

Organic-inorganic halide perovskite materials are emerging as a new class of photoelectric materials for its low cost, easy preparation, and, especially, outstanding optoelectronic properties. Although tremendous efforts have been made on the regulation and optimization of perovskite materials and their microscopic electrical properties for high-efficiency solar cells, few reports focus on the evolution of electrical properties with temperature changes, especially at the microscopic scale, which will directly affect the device performances at varying temperatures. Here, we map the contact potential difference and photocurrent distribution of MAPbI3 at different temperatures in situ by Kelvin probe force microscopy and conductive atomic force microscopy, emphasizing the different influences of variable temperature and phase transition on the photoelectric properties of grains and grain boundaries (GBs). It is discovered that both the Fermi level and photocurrent decrease as the sample is heated from 30 to 80 °C gradually because of the variation of effective carrier concentration and the degradation of carrier mobility implicated by lattice vibration scattering. The difference between the Fermi level at GBs and that on the grains ascends first and then descends, peaking at 50 °C, near which MAPbI3 transforms from a tetragonal phase to a cubic phase. This peak is speculated as a comprehensive consequence of the increasing difference of the Fermi level of semiconductors with different doping concentrations and the converging properties of grains and GBs with the temperature rising because the lower ion activation energy of the cubic phase at higher temperatures facilitates greatly the ions' movement between grains and GB. The variation trend of the difference of the photocurrent is the same. These findings advance the knowledge on the temperature-induced variations of microscopic photoelectrical properties of organic-inorganic hybrid perovskite materials, which may guide the development of strategies for improving their thermal stability.

11.
J Am Chem Soc ; 141(17): 7005-7013, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30933480

RESUMO

Ni or Co is commonly required in efficient electrocatalysts for oxygen evolution reaction (OER). Although Fe is much more abundant and cheaper, full-Fe or Fe-rich catalysts suffer from insufficient activity. Herein, we discover that Se-doping can drastically promote OER on FeOOH and develop a facile on-site electrochemical activation strategy for achieving such a Se-doped FeOOH electrode via an FeSe precatalyst. Theoretical analysis and systematic experiments prove that Se-doping enables FeOOH as an efficient and low-cost OER electrocatalyst. By optimizing the electrode structure, an industrial-level OER current output of 500 mA cm-2 is secured at a low overpotential of 348 mV. The application of such an Fe-rich OER electrode in a practical solar-driven water splitting system demonstrates a high and stable solar-to-hydrogen efficiency of 18.55%, making the strategy promising for exploring new cost-effective and highly active electrocatalysts for clean hydrogen production.

12.
Nat Commun ; 10(1): 1278, 2019 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-30894539

RESUMO

Although single-atomically dispersed metal-Nx on carbon support (M-NC) has great potential in heterogeneous catalysis, the scalable synthesis of such single-atom catalysts (SACs) with high-loading metal-Nx is greatly challenging since the loading and single-atomic dispersion have to be balanced at high temperature for forming metal-Nx. Herein, we develop a general cascade anchoring strategy for the mass production of a series of M-NC SACs with a metal loading up to 12.1 wt%. Systematic investigation reveals that the chelation of metal ions, physical isolation of chelate complex upon high loading, and the binding with N-species at elevated temperature are essential to achieving high-loading M-NC SACs. As a demonstration, high-loading Fe-NC SAC shows superior electrocatalytic performance for O2 reduction and Ni-NC SAC exhibits high electrocatalytic activity for CO2 reduction. The strategy paves a universal way to produce stable M-NC SAC with high-density metal-Nx sites for diverse high-performance applications.

13.
Adv Sci (Weinh) ; 6(5): 1801810, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30886804

RESUMO

Germanium diselenide (GeSe2) has recently emerged as a new member of in-plane anisotropic 2D materials, notable for its wide bandgap of 2.74 eV, excellent air stability, and high performance in polarization-sensitive photodetection. However, the interlayer interaction in GeSe2 has never been reported, which usually plays an important role in layer-number-dependent physical properties. Here, the interlayer coupling in GeSe2 is systematically investigated from theory to experiment. Unexpectedly, all of density functional theory (DFT) calculations about layer-dependent band structures, cleavage energy, binding energy, translation energy, and interlayer differential charge density demonstrate the much weaker interlayer interaction in GeSe2 when compared with black phosphorus (BP). Furthermore, both thickness-dependent and temperature-dependent Raman spectra of GeSe2 flakes, which exhibit no detectable changes of Raman peaks with the increase in thickness and a small first-order temperature coefficient of -0.0095 cm-1 K-1, respectively, experimentally confirm the weakly coupled layers in GeSe2. The results establish GeSe2 as an unusual member of in-plane anisotropic 2D materials with weak interlayer interaction.

14.
Chem Commun (Camb) ; 55(26): 3781-3784, 2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30864580

RESUMO

Combining ultrasmall NiS2 nanodots with three-dimensional carnation-like CoS2 microstructures is demonstrated to be able to enhance the electrocatalytic activities for both the oxygen and hydrogen evolution reactions, leading to efficient overall alkaline water splitting.

15.
J Nanosci Nanotechnol ; 19(6): 3669-3672, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30744804

RESUMO

Organic-inorganic hybrid perovskite single crystals have attracted much attention due to their superior optoelectronic properties. Herein, we report a facile vapor-solution sequential route to prepare single-crystalline nanosheets of hybrid lead triiodide perovskite. It is found that this two-step deposition is able to fabricate sizeable high-quality single-crystalline nanosheets with no need of delicate control of crystallization conditions such as concentration or temperature for normal single crystal growth. The resulting perovskite nanosheets show good reproducibility and single crystallinity with bright and uniform photoluminescence. Our study provides a promising strategy for scalable fabrication of perovskite single crystals with great potential in optoelectronic applications.

16.
ACS Appl Mater Interfaces ; 10(42): 35904-35910, 2018 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-30265514

RESUMO

Doping unary transition-metal phosphides (TMPs) by secondary metal is a powerful method to improve their catalytic activity for electrochemical oxygen evolution reaction (OER). However, the composition-activity relationship of such doping has not been systematically investigated yet because of the challenge in constructing bimetal TMPs with continuously variable composition while keeping homogenous elemental distribution. Herein, we develop a strategy of using bimetal Prussian blue analogues with homogenous elemental distribution at molecular scale as an ideal platform to achieve bimetal cobalt-iron phosphides (Co1- xFe xP) with a continuously changeable Co/Fe ratio (0 < x < 1) and uniform metal distribution. Such a system allows us to draw out a composition-activity volcano profile of Co1- xFe xP for OER. By optimizing the composition, the best catalytic activity is obtained at the Co/Fe ratio of 1.63 in Co1- xFe xP with small overpotentials of 230 and 268 mV at 10 and 100 mA cm-2, respectively, which outperform most of the reported TMPs. These results may inspire the use of multicomponent molecular platforms to understand composition-dependent performance and explore highly efficient catalysts for diverse applications.

17.
J Am Chem Soc ; 140(37): 11705-11715, 2018 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-30110545

RESUMO

Despite the recent surge of interest in inorganic lead halide perovskite nanocrystals, there are still significant gaps in their stability disturbance and the understanding of their destabilization, assembly, and growth processes. Here, we discover that polar solvent molecules can induce the lattice distortion of ligand-stabilized cubic CsPbI3, leading to the phase transition into orthorhombic phase, which is unfavorable for photovoltaic applications. Such lattice distortion triggers the dipole moment on CsPbI3 nanocubes, which subsequently initiates the hierarchical self-assembly of CsPbI3 nanocubes into single-crystalline nanowires. The systematic investigations and in situ monitoring on the kinetics of the self-assembly process disclose that the more amount or the stronger polarity of solvent can induce the more rapid self-assembly and phase transition. These results not only elucidate the destabilization mechanism of cubic CsPbI3 nanocrystals, but also open up opportunities to synthesize and store cubic CsPbI3 for their practical applications in photovoltaics and optoelectronics.

18.
J Am Chem Soc ; 140(37): 11716-11725, 2018 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-30153411

RESUMO

All-inorganic lead halide perovskites demonstrate improved thermal stability over the organic-inorganic halide perovskites, but the cubic α-CsPbI3 with the most appropriate bandgap for light harvesting is not structurally stable at room temperature and spontaneously transforms into the undesired orthorhombic δ-CsPbI3. Here, we present a new member of black-phase thin films of all-inorganic perovskites for high-efficiency photovoltaics, the orthorhombic γ-CsPbI3 thin films with intrinsic thermodynamic stability and ideal electronic structure. Exempt from introducing organic ligands or incorporating mixed cations/anions into the crystal lattice, we stabilize the γ-CsPbI3 thin films by a simple solution process in which a small amount of H2O manipulates the size-dependent phase formation through a proton transfer reaction. Theoretical calculations coupled with experiments show that γ-CsPbI3 with a lower surface free energy becomes thermodynamically preferred over δ-CsPbI3 at surface areas greater than 8600 m2/mol and exhibits comparable optoelectronic properties to α-CsPbI3. Consequently, γ-CsPbI3-based solar cells display a highly reproducible efficiency of 11.3%, among the highest records for CsPbI3 thin-film solar cells, with robust stability in ambient atmosphere for months and continuous operating conditions for hours. Our study provides a novel and fundamental perspective to overcome the Achilles' heel of the inorganic lead iodide perovskite and opens it up for high-performance optoelectronic devices.

19.
Chem Commun (Camb) ; 54(59): 8190-8193, 2018 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-29971312

RESUMO

A facile and scalable solid-state synthesis strategy is developed to produce hierarchical coralline-like nanostructured electrocatalysts with cobalt nanoparticles and Co-NX sites for efficient oxygen reduction reaction, opening up an avenue for the mass production of non-precious metal catalysts for metal-air batteries and fuel cells, etc.

20.
Angew Chem Int Ed Engl ; 57(34): 10959-10965, 2018 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-29953706

RESUMO

A readily available small molecular hole-transporting material (HTM), OMe-TATPyr, was synthesized and tested in perovskite solar cells (PSCs). OMe-TATPyr is a two-dimensional π-conjugated molecule with a pyrene core and four phenyl-thiophene bridged triarylamine groups. It can be readily synthesized in gram scale with a low lab cost of around US$ 50 g-1 . The incorporation of the phenyl-thiophene units in OMe-TATPyr are beneficial for not only carrier transportation through improved charge delocalization and intermolecular stacking, but also potential trap passivation via Pb-S interaction as supported by depth-profiling XPS, photoluminescence, and electrochemical impedance analysis. As a result, an impressive best power conversion efficiency (PCE) of up to 20.6 % and an average PCE of 20.0 % with good stability has been achieved for mixed-cation PSCs with OMe-TATPyr with an area of 0.09 cm2 . A device with an area of 1.08 cm2 based on OMe-TATPyr demonstrates a PCE of 17.3 %.

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