Alkali Metal Species Research Articles

Frustrated Lewis pairs reactivity across the periodic table: The 2024 Catalysis Award Lecture

This article presents an overview of some of our developments of the chemistry of “frustrated Lewis pairs” (FLPs). We begin with a brief outline of the foundations of this discovery and applications of FLPs in hydrogenations. Recent advances in asymmetric hydrogenations and CO2 reduction are discussed. Early studies of FLPs with alkynes and olefins are introduced and shown to lead to the more recent uncovering of phosphino-phosphination reactions, affording a route to dissymmetric bidentate phosphines, a class of understudied ligands for transition metal catalysis. The concept of FLP is further expanding into alkali metal species, with applications in the chemistry with CO or H2 as well as Fischer–Tropsch chemistry. Efforts to use FLPs to model the reduction of N2 in Haber–Bosch type chemistry are also discussed. The concept of FLPs is applied to xenon difluoride chemistry and the fluorination of electron deficient boranes and borates affording new anions that offer potential applications in catalysis. Finally, the broad scope of chemistry where FLPs are being applied is briefly highlighted, demonstrating the impact of this concept around the world and across the periodic table.

Capacitance enhancement by ion-laminated borophene-like layered materials

Atomically flat two-dimensional networks of boron are attracting attention as post-graphene materials. An introduction of cations between the boron atomic layers can exhibit unique electronic functions that are not achieved by neutral graphene or its derivatives. In the present study, we propose a synthesis strategy for ion-laminated boron layered materials in a solution phase, which enables the preparation of analogs by changing the alkali-metal species. The introduction of large cations extends the thermal range of the liquid-crystal phases because of weakened ionic interactions between borophene-like layers. An investigation of the capacitance of ion-laminated structures revealed a 105-fold or better increase in capacitance when the borophene-like materials were introduced between electrodes. That is difficult for general materials since the dielectric constant of common materials is below several thousand.

Respirator-inspired shielding and catalytic oxidation strategies for smoke-suppression polymers, enhancing fire safety.

Polymeric materials pose potential fire hazards to both humans and property because of their intrinsic flammability and the toxic smoke generated by them upon burning. Lowering the risk by relying on traditional firefighting approaches is not timely and sufficient. Herein, analogous to wearing intelligent and responsive respirators, we introduced a universal smoke-suppression and flame-retardant strategy for flammable materials by forming a shield for protection and catalytic oxidation of smoke. Incorporating ethylenediaminetetraacetic acid tripotassium salt dihydrate (EDTA-K3·2H2O) into FPUF promotes rearrangement and cross-linking into char in the condensed phase during fire exposure. Additionally, the resulting alkali metal species act as active catalysts to further oxidize smoke, enhancing fire safety performance. Taking flexible polyurethane foam (FPUF) as an example, even in the absence of traditional flame-retardant elements, this foam demonstrates a significant reduction in specific smoke density (-54%) and total smoke release (-45%) for flexible polyurethane foam (FPUF), a high limiting oxygen index of 26.1%, rapid self-extinguishing performance, and robust overall mechanical properties. Moreover, this work offers exceptional fire protection for epoxy resin and waterborne polyurethane as well. Our work provides a facile strategy inspired by the protection of a respirator for high-performance firefighting.

Study on the comprehensive influence of Si-Al-based additives on hydrogen production and K deposition during biomass gasification

Study on the comprehensive influence of Si-Al-based additives on hydrogen production and K deposition during biomass gasification

Structure, Electronic Properties and Nonlinear Optical Properties of Silagraphdiyne (SiGDY): The Role of Alkali Metal Species

Structure, Electronic Properties and Nonlinear Optical Properties of Silagraphdiyne (SiGDY): The Role of Alkali Metal Species

Experimental research of alkali metals modified Mg/DOBDC metal organic framework as high capacity CO2 adsorbent

Experimental research of alkali metals modified Mg/DOBDC metal organic framework as high capacity CO2 adsorbent

Compilation of Ionic Clusters with the Rock Salt Structure: Accurate Benchmark Thermochemical Data, Assessment of Quantum Chemistry Methods, and the Convergence Behavior of Lattice Energies.

In the present study, computational quantum chemistry is used to obtain lattice energies (LEs) for a range of ionic clusters with the NaCl structure. Specifically, the compounds include NaF, NaCl, MgO, MgS, KF, CaO, and CaS clusters, (MX)n, with n = 1, 2, 4, 6, 8, 12, 16, 24, 32, 40, 50, 60, 75, 90, and 108. The highest-level W2 and W1X-2 methods are applied to the small clusters with n = 1 to 8 (the MX35 data set). The assessment with MX35 shows that, for the calculation of geometries and vibrational frequencies, the PBE0-D3(BJ) and PBE-D3(BJ) DFT methods are reasonable, but the calculation of atomization energies is more challenging. This is a result of different systematic deviations for clusters of different species. Thus, species-specific adjustments are applied for larger clusters, which are calculated with the DuT-D3 double-hybrid DFT method, the MN15 DFT method, and the PM7 semi-empirical method. They yield smoothly converging LEs to the bulk values. It is also found that, for the alkali-metal species, the LEs for a single molecule are ∼70% of the bulk values, while for the alkali-earth species, they are ∼80%. This has enabled a straightforward means to the first-principles estimation of LEs for similarly structured ionic compounds.

Oxidative catalytic steam gasification of sugarcane bagasse for hydrogen rich syngas production

Oxidative catalytic steam gasification of sugarcane bagasse for hydrogen rich syngas production

Volatile-char interactions during biomass pyrolysis: Effect of biomass acid-washing pretreatment

Volatile-char interactions during biomass pyrolysis: Effect of biomass acid-washing pretreatment

Molten salt-mediated carbon capture and conversion

Molten salt-mediated carbon capture and conversion

Efficient enhancement of the anti-KCl-poisoning performance for V2O5-WO3/TiO2 catalysts by Ce(SO4)2 modification

Efficient enhancement of the anti-KCl-poisoning performance for V2O5-WO3/TiO2 catalysts by Ce(SO4)2 modification

Alteration of Oxygen Evolution Mechanisms in Layered LiCoO2 Structures By Intercalation of Alkali Metal Ions

The word ‘Sustainability’, including carbon neutrality, has dominated the direction of social development over the past decade. In particular, energy conversion reactions through electrochemical methods are one of the efficient methods of obtaining small carbon footprint fuels. The oxygen evolution reaction (OER) is a key step in determining the overall reaction efficiency of fuel-related electrochemical reactions such as CO2 reduction reaction and H2 evolution reaction. However, electron transfer is sluggish for OER due to 4 electrons per one O2 molecule. This promotes multiple studies on the metal oxide electrocatalyst structure. The Alkali-transition metal oxides with the layered structure are one of the attractive OER electrocatalyst series. For example, lithium cobalt oxide (LiCoO2, LCO) presented OER activity through Li+ extraction (delithiation) from the lattice structure. In this work, we investigated the insertion effect of large alkaline cations (A+: Na+, K+, and Cs+) at the delithiated LCO for OER activity and stability. The intercalations of hydrated Na+ and K+ induced significant phase transformation of the delithiated LCO structure. In addition, the relative ratio between Co and alkali metal species determined the average Co oxidation state of LCO. We found that OER activity was improved in the order of Li+ < Na+ < K+, which was associated with the increased Co valence state and the Co-O bond covalency. Consistently, density functional theory (DFT) simulation also predicted the formation of efficient OER active sites by the K+ insertion. In comparison, Cs+ insertion exhibited the highest OER activity and demonstrated different OER processes. Due to the larger Cs+ size, the cation insertion was predominantly achieved at the delithiated LCO surface, resulting in imposing tensile strain to the surface edge. This catalyst showed the significant pH dependency on the OER property, suggesting the lattice-oxygen-based pathway for LCO. However, the bulk structure was preserved with little phase transformation, demonstrating better OER stability than others. In the presentation, I will discuss the catalytic activity responsible for the cation sizes and two different mechanisms in detail. Figure 1

Influence of water leaching on alkali-induced slagging properties of biomass straw

Influence of water leaching on alkali-induced slagging properties of biomass straw

Robust Mg(Ca)Zr-Doped Acid-Base Bifunctional Mesoporous Silica and Their Applications in the Deacetalization-Knoevenagel Reaction.

A series of Mg(Ca)Zr-doped acid-base bifunctional mesoporous silica were synthesized to study the impact of the one-step or two-step impregnation method on material structure. The two-step method seems to be a better way to synthesize metal-based functionalized catalyst and their catalytic performance is investigated using deacetalization-Knoevenagel reaction as the probe reaction. The coexisting dual active sites and suitable designing routes endowed highly efficient (Conv. >99.6%, Sel. >99.8%) and robust stability (10 consecutive cycles) of these materials. The present process succeeded in preparing catalysts decorated with acid-base sites by doping acidic and alkali metal species rather than grafting organic groups.

Experimental investigation on the ignition and combustion characteristics of pyrolyzed char and bituminous coal blends

Experimental investigation on the ignition and combustion characteristics of pyrolyzed char and bituminous coal blends

Mechanism of catalytic tar reforming over biochar: Description of volatile-H2O-char interaction

Mechanism of catalytic tar reforming over biochar: Description of volatile-H2O-char interaction

Synthetic magnetic fields for cold erbium atoms

The implementation of the fractional quantum Hall effect in ultracold atomic quantum gases remains, despite substantial advances in the field, a major challenge. Since atoms are electrically neutral, a key ingredient is the generation of sufficiently strong artificial gauge fields. Here we theoretically investigate the synthetization of such fields for bosonic erbium atoms by phase imprinting with two counterpropagating optical Raman beams. Given the nonvanishing orbital angular momentum of the rare-earth atomic species erbium in the electronic ground state and the availability of narrow-line transitions, heating from photon scattering is expected to be lower than in atomic alkali-metal species. We give a parameter regime for which strong synthetic magnetic fields with good spatial homogeneity are predicted. We also estimate the size of the Laughlin gap expected from the s-wave contribution of the interactions for typical experimental parameters of a two-dimensional atomic erbium microcloud. Our analysis shows that cold rare-earth atomic ensembles are highly attractive candidate systems for experimental explorations of the fractional quantum Hall regime.

Effect of sodium and calcium on the ash fusion temperatures of Zhundong coal

The effect of sodium and calcium on the ash fusion temperatures (AFTs) of Zhundong coal was investigated in this study using an ash fusibility tester combined with X-ray diffraction technology. The results indicate that the AFTs of Zhundong coal are closely related to the content of sodium and calcium in coal ash compounds. The pretreatment of the raw coal with water leaching and hydrochloric acid leaching can remarkably enhance the AFTs, which is attributed to the removal of inherent alkali metal species in coal. The AFTs decrease first and then increase not only with the increment of Na2CO3 loading but also with the increment of CaO addition, and the minimum AFTs were, respectively, reached at 15 mass% Na2CO3 loading and 10 mass% CaO addition. The transformation of hematite during ashing of Zhundong coal with different Na2CO3 loadings gives much contribution to the reduction of the AFTs. Meanwhile, the formation of KSi3AlO8 and muscovite accounts for the rising AFTs beyond the loading amount of 15 mass% Na2CO3. For Zhundong coal-added CaO, the drop of AFTs maybe results from the formation of low-melting iron species and eutectic salts, whereas the growing AFTs may be ascribed to the overdosed lime with high melting point and the formation of Ca2SiO4 during ashing.

Effects of pump laser power density on the hybrid optically pumped comagnetometer for rotation sensing.

We investigate the effects of pump laser power density on the hybrid optically pumped comagnetometer operated in the spin-exchange relaxation-free (SERF) regime. The analytic steady-state output model for the comagnetometer considering two alkali metal species and one nuclear species is presented for the first time. And the effects of pump laser power density on the rotation sensitivity, suppression of low-frequency magnetic noise and long-term stability of the comagnetometer are studied experimentally. The results indicate that when the product of pumping rate and density ratio of pumped atom to probed atom is equal to the spin relaxation rate of the probed atom, the maximum response and highest sensitivity of the comagnetometer are achieved. However, the suppression of low-frequency magnetic noise and long-term stability improve with the increasing of pump laser power density due to the increasing of nuclear spin polarization. Our focus is to optimize the performance of the comagnetometer for rotation sensing, but the theory and method presented here are relevant to all applications of the hybrid optical pumping technique.

Enhanced dual resistance to alkali metal and phosphate poisoning: Mo modifying vanadium-titanate nanotubes SCR catalyst

Enhanced dual resistance to alkali metal and phosphate poisoning: Mo modifying vanadium-titanate nanotubes SCR catalyst