A major bottleneck delaying the further commercialization of thin-film solar cells based on hybrid organohalide lead perovskites is interface loss in state-of-the-art devices. We present a generic ...interface architecture that combines solution-processed, reliable, and cost-efficient hole-transporting materials without compromising efficiency, stability, or scalability of perovskite solar cells. Tantalum-doped tungsten oxide (Ta-WOₓ)/conjugated polymer multilayers offer a surprisingly small interface barrier and form quasi-ohmic contacts universally with various scalable conjugated polymers. In a simple device with regular planar architecture and a self-assembled monolayer, Ta-WOₓ–doped interface–based perovskite solar cells achieve maximum efficiencies of 21.2% and offer more than 1000 hours of light stability. By eliminating additional ionic dopants, these findings open up the entire class of organics as scalable hole-transporting materials for perovskite solar cells.
A tantalum-catalyzed solvent-free approach for the construction of amide bonds with 1-(trimethylsilyl)imidazole is developed, and the mild reaction conditions are applicable to a wide variety of ...electrophilic amino acid homologues. This approach delivers a new class of peptides in high yields without any epimerization.
Cocatalysts have been extensively used to promote water oxidation efficiency in solar‐to‐chemical energy conversion, but the influence of interface compatibility between semiconductor and cocatalyst ...has been rarely addressed. Here we demonstrate a feasible strategy of interface wettability modification to enhance water oxidation efficiency of the state‐of‐the‐art CoOx/Ta3N5 system. When the hydrophobic feature of a Ta3N5 semiconductor was modulated to a hydrophilic one by in situ or ex situ surface coating with a magnesia nanolayer (2–5 nm), the interfacial contact between the hydrophilic CoOx cocatalyst and the modified hydrophilic Ta3N5 semiconductor was greatly improved. Consequently, the visible‐light‐driven photocatalytic oxygen evolution rate of the resulting CoOx/MgO(in)–Ta3N5 photocatalyst is ca. 23 times that of the pristine Ta3N5 sample, with a new record (11.3 %) of apparent quantum efficiency (AQE) under 500–600 nm illumination.
Hydrophilic interface modification of a CoOx‐modified Ta3N5 photocatalyst with a magnesia nanolayer significantly improves its water oxidation efficiency under visible light irradiation. The essential roles of the interface modification are proposed to enhance the interfacial coverage of the CoOx/Ta3N5 photocatalyst and to decrease the defect density of Ta3N5 semiconductor. AQE=apparent quantum efficiency.
Transition metal dichalcogenides (TMDs) have become a playground for exploring rich physical phenomena like superconductivity and charge-density-waves (CDW). Here, we report the synthesis of the ...atom-thin TaSe2 with a rare 3R phase and enhanced superconductivity. The 3R phase is achieved by an ambient pressure chemical vapor deposition (CVD) strategy and confirmed by the high-resolution aberration-corrected STEM. Low-temperature transport data reveal an enhanced superconducting transition temperature (T c) of 1.6 K in the 3R-TaSe2, which undoubtedly breaks the traditional perception of TaSe2 crystal as a material with T c close to 0 K. This work demonstrates the strength of ambient pressure CVD in the exploration of crystal polymorphism, highlights a decisive role of layer stacking order in the superconducting transition, and provides fresh insights on manipulating crystal structures to gain access to enhanced T c.
A Lewis-acid-catalyzed method for the substrate-directed formation of peptide bonds has been developed, and this powerful approach is utilized for the new “remote” activation of carboxyl groups under ...solvent-free conditions. The presented method has the following advantages: (1) the high-yielding peptide synthesis uses a tantalum catalyst for any amino acids; (2) the reaction proceeds without any racemization; (3) the new substrate-directed chemical ligation using the titanium catalyst is applicable to convergent peptide synthesis. These advantages overcome some of the unresolved problems in classical peptide synthesis.
Ag(Nb
0.8
Ta
0.2
)O
3
is used here as a model system to shed light on the nature of the low temperature phase behavior of the unsubstituted parent compound AgNbO
3
, which is an important material ...for high-power energy storage applications. The three dielectric anomalies previously identified as M
1
↔ M
2
,
T
f
and M
2
↔ M
3
transitions in AgNbO
3
ceramics are found to be intimately related to the polarization the behavior of the B-site cations. In particular, the M
1
↔ M
2
transition is found to involve the disappearance of original ferroelectric polar structure in the M
1
phase. Analysis of weak-field and strong field hysteresis loops in the M
2
region below
T
f
suggests the presence of a weakly-polar structure exhibiting antipolar behavior (
i.e.
, a non-compensated antiferroelectric), which can be considered as ferrielectric (FIE). Modeling of the permittivity data using the Curie-Weiss law indicates that the Curie temperature is close to the freezing temperature,
T
f
, which can be regarded as the Curie point of the FIE phase. Substitution by Ta
5+
in this system enhances the stability of the weakly polar/antiferroelectric state, giving rise to an increased energy storage density of 3.7 J cm
−3
under an applied field of 27 MV m
−1
, one of the highest values ever reported for a dielectric ceramic. Furthermore, the energy storage capability remains approximately constant at around 3 J cm
−3
up to 100 °C, at an applied field of 22 MV m
−1
.
Ag(Nb
0.8
Ta
0.2
)O
3
is used here as a model system to shed light on the nature of the low temperature phase behavior of the unsubstituted parent compound AgNbO
3
, which is an important material for high-power energy storage applications.
Atom‐economic and regioselective Csp3
−Csp3
bond formation has been achieved by rapid C−H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2, ...and a ureate N,O‐chelating‐ligand salt gives catalytic systems prepared in situ that can realize high yields of β‐alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C−H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.
Speed by design: Atom‐economic and regioselective Csp3
−Csp3
bond formation has been achieved by rapid C−H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2 and a ureate N,O‐chelating‐ligand salt provides high yields of β‐alkylated aniline derivatives.
This study provides scenarios toward 2050 for the demand of five metals in electricity production, cars, and electronic appliances. The metals considered are copper, tantalum, neodymium, cobalt, and ...lithium. The study shows how highly technology-specific data on products and material flows can be used in integrated assessment models to assess global resource and metal demand. We use the Shared Socio-economic Pathways as implemented by the IMAGE integrated assessment model as a starting point. This allows us to translate information on the use of electronic appliances, cars, and renewable energy technologies into quantitative data on metal flows, through application of metal content estimates in combination with a dynamic stock model. Results show that total demand for copper, neodymium, and tantalum might increase by a factor of roughly 2 to 3.2, mostly as a result of population and GDP growth. The demand for lithium and cobalt is expected to increase much more, by a factor 10 to more than 20, as a result of future (hybrid) electric car purchases. This means that not just demographics, but also climate policies can strongly increase metal demand. This shows the importance of studying the issues of climate change and resource depletion together, in one modeling framework.
A novel heterobimetallic tantalum/iridium hydrido complex, {Ta(CH2 t Bu)3}{IrH2(Cp*)} 1, featuring a very short metal–metal bond, has been isolated through an original alkane elimination route from ...Ta(CH t Bu)(CH2 t Bu)3 and Cp*IrH4. This molecular precursor has been used to synthesize well-defined silica-supported low-coordinate heterobimetallic hydrido species SiOTa(CH2 t Bu)2{IrH2(Cp*)}, 5, and SiOTa(CH2 t Bu)H{IrH2(Cp*)}, 6, using a surface organometallic chemistry (SOMC) approach. The SOMC methodology prevents undesired dimerization as encountered in solution and leading to a tetranuclear species {Ta(CH2 t Bu)2}(Cp*IrH)2, 4. This approach therefore allows access to unique low-coordinate species not attainable in solution. These original supported Ta/Ir species exhibit drastically enhanced catalytic performances in H/D exchange reactions with respect to (i) monometallic analogues as well as (ii) homogeneous systems. In particular, material 6 promotes the H/D exchange between fluorobenzene and C6D6 or D2 as deuterium sources with excellent productivity (TON up to 1422; TOF up to 23.3 h–1) under mild conditions (25 °C, sub-atmospheric D2 pressure) without any additives.
The room‐temperature reaction of Cp*TaCl4 with LiBH4⋅THF followed by addition of S2CPPh3 results in pentahydridodiborate species (Cp*Ta)2(μ,η2:η2‐B2H5)(μ‐H)(κ2,μ‐S2CH2)2 (1), a classical B2H5− ion ...stabilized by the binuclear tantalum template. Theoretical studies and bonding analysis established that the unusual stability of B2H5− in 1 is mainly due to the stabilization of sp2‐B center by electron donation from tantalum. Reactions to replace the hydrogens attached to the diborane moiety in 1 with a 2 e {M(CO)4} fragment (M=Mo or W) resulted in simple adducts, {(Cp*Ta)(CH2S2)}2(B2H5)(H){M(CO)3} (6: M=Mo and 7: M=W), that retained the diborane(5) unit.
Isolation of a classical diborane(5) complex of tantalum was achieved by the room‐temperature reaction of Cp*TaCl4 with LiBH4⋅THF followed by addition of S2CPPh3. Reactivity with metal carbonyls was also explored.
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