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Chemistry of Select Electroceramic Materials: Lead zirconium titanate (PZT) indium tin oxide (ITO) and zinc oxide.
Abstract not provided.
Isolated copper–tin atomic interfaces tuning electrocatalytic CO 2 conversion
Direct experimental observations of the interface structure can provide vital insights into heterogeneous catalysis. Examples of interface design based on single atom and surface science are, however, extremely rare. Here, we report Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, for efficient electrocatalytic CO 2 reduction. The unique geometric and electronic structure of the Cu–Sn surface alloys (Cu 97 Sn 3 and Cu 99 Sn 1 ) enables distinct catalytic selectivity from pure Cu 100 and Cu 70 Sn 30 bulk alloy. The Cu 97 Sn 3 catalyst achieves a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell, where a high CO current density of 100 mA cm –2 is obtained at an overpotential of 340 mV. Density functional theory simulation reveals that it is not only the elemental composition that dictates the electrocatalytic reactivity of Cu–Sn alloys; the local coordination environment of atomically dispersed, isolated Cu–Sn bonding plays the most critical role.
Structural characterization of tin in toothpaste by dynamic nuclear polarization enhanced 119 Sn solid-state NMR spectroscopy
Stannous fluoride (SnF 2 ) is an effective fluoride source and antimicrobial agent that is widely used in commercial toothpaste formulations. The antimicrobial activity of SnF 2 is partly attributed to the presence of Sn(II) ions. However, it is challenging to directly determine the Sn speciation and oxidation state within commercially available toothpaste products due to the low weight loading of SnF 2 (0.454 wt% SnF 2 , 0.34 wt% Sn) and the amorphous, semi-solid nature of the toothpaste. Here, we show that dynamic nuclear polarization (DNP) enables 119 Sn solid-state NMR experiments that can probe the Sn speciation within commercially available toothpaste. Solid-state NMR experiments on SnF 2 and SnF 4 show that 19 F isotropic chemical shift and 119 Sn chemical shift anisotropy (CSA) are highly sensitive to the Sn oxidation state. DNP-enhanced 119 Sn magic-angle turning (MAT) 2D NMR spectra of toothpastes resolve Sn(II) and Sn(IV) by their 119 Sn chemical shift tensor parameters. Fits of DNP-enhanced 1D 1 H → 119 Sn solid-state NMR spectra allow the populations of Sn(II) and Sn(IV) within the toothpastes to be estimated. This analysis reveals that three of the four commercially available toothpastes contained at least 80% Sn(II), whereas one of the toothpaste contained a significantly higher amount of Sn(IV).
Bilayer electrified-membrane with pair-atom tin catalysts for near-complete conversion of low concentration nitrate to dinitrogen
Not provided.
High current density electroreduction of CO 2 into formate with tin oxide nanospheres
In this study, we demonstrate three-dimensional (3D) hollow nanosphere electrocatalysts for CO 2 conversion into formate with excellent H-Cell performance and industrially-relevant current density in a 25 cm 2 membrane electrode assembly electrolyzer device. Varying calcination temperature maximized formate production via optimizing the crystallinity and particle size of the constituent SnO 2 nanoparticles. The best performing SnO 2 nanosphere catalysts contained ~ 7.5 nm nanocrystals and produced 71–81% formate Faradaic efficiency (FE) between -0.9 V and -1.3 V vs. the reversible hydrogen electrode (RHE) at a maximum formate partial current density of 73 ± 2 mA cm geo -2 at -1.3 V vs. RHE. The higher performance of nanosphere catalysts over SnO 2 nanoparticles and commercially-available catalyst could be ascribed to their initial structure providing higher electrochemical surface area and preventing extensive nanocrystal growth during CO 2 reduction. Our results are among the highest performance reported for SnO 2 electrocatalysts in aqueous H-cells. We observed an average 68 ± 8% FE over 35 h of operation with multiple on/off cycles. In situ Raman and time-dependent X-ray diffraction measurements identified metallic Sn as electrocatalytic active sites during long-term operation. Further evaluation in a 25 cm 2 electrolyzer cell demonstrated impressive performance with a sustained current density of 500 mA cm geo -2 and an average 75 ± 6% formate FE over 24 h of operation. Our results provide additional design concepts for boosting the performance of formate-producing catalysts.
Pairwise semi-hydrogenation of alkyne to cis -alkene on platinum-tin intermetallic compounds
Intermetallic PtSn nanoparticles leads to pairwise-hydrogenation of alkynes to the corresponding cis -alkenes, satisfying both high stereoselectivity and high chemoselectivity.
Ultrathin alumina passivation for improved photoelectrochemical water oxidation catalysis of tin oxide sensitized by a phosphonate-functionalized perylene diimide first without, and then with, CoOy
Previously, a photoanode composed of nanostructured SnO 2 coated with the perylene diimide dye N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI) plus photoelectrochemically deposited cobalt oxide (CoO y ) was shown to photoelectrochemically oxidize water at 31 ± 7% faradaic efficiency. A non-ideal part of that prior system is that the addition of the known CoO y water oxidation catalyst (WOC) resulted in a reduction of the total photocurrent rather than the anticipated increase, due to an increase in charge-carrier recombination. Herein, we show deposition of an ultrathin alumina overlayer applied by atomic layer deposition (ALD) on the SnO 2 /PMPDI photoanode can improve the photoactivity and catalytic activity of the system; the addition a ca. 1 nm-thick AlO x layer deposited on a 4000 nm (i.e., 4 micron) thick mesoporous anode system can and does have a positive, 2.5-fold improvement in the steady-state photocurrent with 29 ± 9% faradaic efficiency vs. the control anode without alumina passivation by reducing charge-carrier recombination. Moreover, ALD-deposited AlO x layer does help support the understanding of the “anti-catalysis” of co-depositing a CoO y WOC on the SnO 2 /PMPDI DS-PECs—specifically the picture of direct CoO y –SnO 2 contact-mediated recombination—but that AlO x layer was unable to improve the photocurrent in a net SnO 2 /PMPDI/AlO x (/CoO y ) system. We attribute the lack of a performance enhancement by CoOy WOC to incomplete coverage of each SnO 2 nanoparticle by the AlO x . Overall, we find the addition of an optimized ultrathin AlOx layer (0.6 nm thick; deposited at 85 °C) improves the SnO 2 /PMPDI/AlO x system's photoactivity by a factor of up to ca. 3-fold with reduced recombination. These results document that metal-oxide passivation by low-temperature ALD can be an effective strategy for improving the water oxidation performance of even nanostructured dye sensitized-photoelectrochemical cell.
Antimony doping to enhance luminescence of tin ($\mathrm{IV}$)-based hybrid metal halides
Lead-based organic–inorganic metal halides (OIMHs) have recently attracted special attention due to their efficient broadband photoluminescence. However, the toxicity of lead poses a challenge for their further development. In this paper we selected Sn(IV) as the metal center to synthesize the environmentally friendly and stable luminescent OIMHs (C 9 H 15 N 3 ) 2 SnCI 8 and C 9 H 15 N 3 ) 2 SnBr 8 (C 9 H 13 N 3 is 1-(2-2-pyridyl)piperazine). Both compounds possess zero-dimensional structures, crystallizing in the monoclinic space group P2 1 /c, and their optical band gaps were experimentally determined to be 3.19 and 2.60 eV, respectively. Under UV excitation at room temperature, (C 9 H 15 N 3 ) 2 SnCI 8 exhibited double-peak emissions centered at 405 and 688 nm, which were attributed to the organic cation and inorganic octahedra, respectively. Upon introducing 5s 2 -lone-pair-containing Sb 3+ in (C 9 H 15 N 3 ) 2 SnCI 8 , self-trapped emission was promoted, and the photoluminescence quantum yield increased from ~1% to ~17.84%. This work suggests effective strategies for finding environmentally friendly stable OIMHs and for further enhancing the luminescence properties through lone-pair-containing cation doping.
Stability and synthesis across barium tin sulfide material space
The underexplored Ba–Sn–S phase space is explored at various temperatures and cation ratios with combinatorial sputtering, crystallizing rocksalt-derived phases, Ba 2 SnS 4 , and Ba 7 Sn 5 S 15 . These findings are supported by DFT computed phase diagrams.
Comparison of the Arrhenius parameters between conventional hydrothermal and microwave-assisted synthesis methods for tin oxide nanoparticles
Microwave (MW) irradiation has emerged as a powerful tool for accelerating materials synthesis, yet the origins of its specific influence on reaction kinetics remain elusive. While multiple studies have attributed the observed enhancements in reaction rates under MW heating to reduced activation energies, other accounts have suggested modifications to the Arrhenius pre-exponential factor as the predominant cause. Distinguishing between these parameters in modern applications of MW processing in nanomaterials requires experimental approaches capable of resolving the dynamic and nuanced structural kinetics that govern MW-assisted chemistry. Here, we combine in-situ synchrotron X-ray total scattering with pair distribution function (PDF) analysis to track the structural evolution of SnO 2 nanoparticles synthesized via MW-assisted and conventional hydrothermal conditions. Avrami modeling and Arrhenius analysis suggest that although MW irradiation yields a higher apparent activation energy, the enhanced crystallization is better explained by a pre-exponential factor several orders of magnitude larger than that of conventional heating. These findings suggest that the MW field induces a higher frequency of successful molecular rearrangements rather than lowering the intrinsic activation barrier. The results contribute further insights clarifying the role of the applied MW field for materials design where MW-specific effects can be deliberately harnessed. Furthermore, this work presents a framework promoting the utility of in-situ PDF characterization coupled with kinetic analysis for developing more sophisticated descriptions of nanoscale transformations for MW-driven reaction kinetics.
Inference of strength and phase transition kinetics in dynamically-compressed tin
Dynamic compression experiments in condensed matter are of interest in part because they provide opportunities to examine material response under extreme conditions; however, the inference of material behavior from dynamic experiments is challenging in the presence of phase transitions exhibiting kinetic processes. Demonstrating an approach to quantitative interpretation of such dynamic experiments, here we present a Bayesian model calibration of strength and phase transformation parameters to data drawn from pulsed power and gas gun shot experiments. The posterior predictions of the Bayesian model capture the experimental measurements and account for the various uncertainties in the experimental configurations. This holistic approach to model calibration utilizing multiple types of experimental data identifies important cross correlations among kinetics, strength, and the phase boundary. Improved insight into potential sources of current model form error is provided by comparing the differences between calibrations against different subsets of the experimental data.
Multi-frame x-ray radiography and image tracking for quantification of expansion in laser-driven tin ejecta microjets
One regime of experimental particle-laden flow study involves ejecta microjets—often defined as a stream of micrometer-scale particles generated through shock interaction with a non-uniform surface and generally travel above 1 km/s. In order to capture the change in characteristics as a function of propagation time, we apply a multi-frame x-ray radiography platform to observe and track the jet transport dynamics. A synchrotron x-ray source allows us to perform quantitative analyses and comparisons between the eight images captured by the imaging system. Observation of a single jet through time allows the use of a cross correlation algorithm to independently track various regions within the jet and quantify the jet expansion over time using normalized area and normalized areal density values. Through a comparison with the calculated values of ballistic transport, these findings show less expansion than expected for ballistically transporting particles. In conclusion, this work combines multi-frame synchrotron radiography with image tracking to establish a foundation for future studies on jet transport and particle interaction dynamics.
Short-range order and longer-range disorder revealed in germanium–tin alloy thin films by extended x-ray absorption fine structure analysis
Short-range order (SRO) in semiconductor alloys, a relatively under-studied structural phenomenon in which local atomic arrangements differ from those of a random solid solution, is investigated in molecular beam epitaxy (MBE)-grown GeSn thin films. A novel preparation technique is used to pattern these films into microscale ribbons that are released from the substrate for extended x-ray absorption fine structure (EXAFS) analysis. The results indicate a strong SRO in which the first shell around Sn atoms is greatly denuded of Sn atoms relative to the nominal atomic composition of the alloy. This effect is more pronounced than that observed recently in GeSn nanowires grown by chemical vapor deposition. Additionally, the presence of a longer-range disorder detected by EXAFS analysis in the shells of atoms more distant from the absorbers is indicative of the defects and inhomogeneous strain present in the MBE-grown films. The evident existence of the SRO in GeSn alloys deposited by different growth methods and in different strain states suggests that SRO is a general phenomenon in the thin films of this metastable solid solution.
The role of substrate on stabilizing new phases of two-dimensional tin
In this work, we investigate the role of substrates in determining the morphologies and electronic structures of two-dimensional (2D) Sn. Here, we use Ir(111) and 2D hexagonal boron nitride (h-BN) predeposited on Ir(111) as substrates. The latter contains Moiré patterns with varying binding strength between h-BN and metal. Using scanning tunneling microscopy and first-principles calculations, we reveal the distinct morphologies of 2D Sn on different substrates. Of particular interest, we discover a new √7 × √7 Sn phase, originating from the local charge transfer with metal beneath the “decoupling” h-BN monolayer at the strongly interacting Moiré region. To the best of our knowledge, this work demonstrates, for the first time via combined experimental and theoretical approach, that new 2D Sn phases can be achieved using Moiré patterns on h-BN/metal. This finding should be instrumental in the development of 2D-based topological materials.
Stable and metastable structures of tin (IV) oxide at high pressure
We have analyzed SnO 2 with a combination of synchrotron X-ray diffraction and X-ray absorption spectroscopy across a pressure range of 0 → 82.9 GPa with thermal annealing by a CO 2 laser allowing access to all of the known high-density polymorphs of SnO 2 , and here report their crystallographic information. The metastability of the post-rutile α -PbO 2 and PdF 2 structures in SnO 2 are investigated by experiment and PW-DFT simulations, revealing a complex energetic landscape and suggesting a significant dependence of the observed phases on the pressure–temperature pathway taken in experiment.
Tin resonance-ionization schemes for atomic- and nuclear-structure studies
Not Available