Ionic conductivity enhancement in solid polymer electrolytes by electrochemical in situ formation of an interpenetrating network

Various overoxidized poly(1H-pyrrole) (PPy), poly(N-methylpyrrole) (PMePy) or poly(3,4-ethylenedioxythiophene) (PEDOT) membranes incorporated into an acrylate-based solid polymer electrolyte matrix (SPE) were directly electrosynthesized by a two-step in situ procedure. The aim was to extend and improve fundamental properties of pure SPE materials. The polymer matrix is based on the cross-linking of glycerol propoxylate (1PO/OH) triacrylate (GPTA) with poly(ethylene glycol) diacrylate (PEGDA) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a conducting salt. A self-standing and flexible polymer electrolyte film is formed during the UV-induced photopolymerization of the acrylate precursors, followed by an electrochemical polymerization of the conducting polymers to form a 3D-IPN. The electrical conductivity of the conducting polymer is destroyed by electrochemical overoxidation in order to convert the conducting polymer into an ion-exchange membrane by introduction of electron-rich groups onto polymer units. The resulting polymer films were characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, differential scanning calorimetry, thermal analysis and infrared spectroscopy. The results of this study show that the combination of a polyacrylate-matrix with ion selective properties of overoxidized CPs leads to new 3D materials with higher ionic conductivity than SPEs and separator or selective ion-exchange membrane properties with good stability by facile fabrication.

Conductive polymers were encapsulated and subsequently overoxidized in an acrylate polymer matrix as potential separator materials via the combination of UV-induced and electrochemical polymerization.     

High ionic conductivity of multivalent cation doped Li6PS5Cl solid electrolytes synthesized by mechanical milling

The performances of next generation all-solid-state batteries might be improved by using multi-valent cation doped Li₆PS₅Cl solid electrolytes. This study provided solid electrolytes at room temperature using planetary ball milling without heat treatment. Li₆PS₅Cl was doped with a variety of multivalent cations, where an electrolyte comprising 98% Li₆PS₅Cl with 2% YCl₃ doping exhibited an ionic conductivity (13 mS cm⁻¹) five times higher than pure Li₆PS₅Cl (2.6 mS cm⁻¹) at 50 °C. However, this difference in ionic conductivity at room temperature was slight. No peak shifts were observed, including in the synchrotron XRD measurements, and the electron diffraction patterns of the nano-crystallites (ca. 10–30 nm) detected using TEM exhibited neither peak shifts nor new peaks. The doping element remained at the grain boundary, likely lowering the grain boundary resistance. These results are expected to offer insights for the development of other lithium-ion conductors for use in all-solid-state batteries.

The performances of next generation all-solid-state batteries might be improved by using multi-valent cation doped Li₆PS₅Cl solid electrolytes.     

Effect of morphological change of copper-oxide fillers on the performance of solid polymer electrolytes for lithium-metal polymer batteries

Solid polymer electrolytes (SPEs) for Li-metal polymer batteries are prepared, in which poly(ethylene oxide) (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and copper-oxide fillers are formulated. Their structural and electrochemical properties are analyzed when the morphology of the copper-oxide fillers has been modulated to spherical or dendritic structure. The ionic conductivity obtained by electrochemical impedance spectroscopy (EIS) has been increased to 1.007 × 10⁻⁴ S cm⁻¹ at 30 °C and 1.368 × 10⁻³ S cm⁻¹ at 60 °C, as the 5 wt% dendritic fillers have been added to the SPEs. This ionic conductivity value is 1.3 times higher than that of 5 wt% spherical filler-contained SPEs. The analyses of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) indicate that the increase of ionic conductivity is due to the remarkable decrease of crystallinity upon the addition of copper-oxide filler into PEO matrix of SPEs. The fabricated SPEs with the dendritic copper-oxide fillers present a total ionic transference number of 0.99 and a lithium-ion transference number of 0.38. More importantly, it presents a stable potential window of 2.0–4.8 V at 25 °C and high thermal stability up to 300 °C. The specific discharge capacity of the prepared cell with the dendritic filler-contained SPEs is measured to be 51 mA h g⁻¹ and 125 mA h g⁻¹ under 0.1 current-rate (C-rate) at 25 °C and 60 °C, respectively. In this study, the ionic conductivity and the electrochemical performance of the PEO-based polymer electrolyte have been evaluated when morphologically different copper-oxide fillers have been incorporated into the PEO matrix. We have also confirmed the safety and the flexibility of the prepared solid polymer electrolytes when they are used in flexible lithium-metal polymer batteries (LMPBs).

Solid polymer electrolytes (SPEs) for Li-metal polymer batteries are prepared, in which poly(ethylene oxide) (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and copper-oxide fillers are formulated.     

Structures and conductivities of stable and metastable Li5GaS4 solid electrolytes

Understanding the differences in the structures and defects in the stable crystalline phase and metastable phase is important for increasing the ionic conductivities of a solid electrolyte. The metastable phase often has higher conductivity than the stable phase. In this study, metastable lithium thiogallate, Li₅GaS₄, was synthesized via mechanochemistry and stable Li₅GaS₄ was obtained by heating the metastable phase. The metastable Li₅GaS₄ sample was found to have an antifluorite-type crystal structure with cationic disorder, while the stable phase was found to have a monoclinic crystal structure, similar to that of another solid electrolyte, Li₅AlS₄. In both the structures, the Ga³⁺ cations were surrounded by four S²⁻ anions in tetrahedral coordination. The conductivity of the metastable phase was determined to be 2.1 × 10⁻⁵ S cm⁻¹ at 25 °C, which is 1000 times greater than that of the monoclinic phase. The high conductivity of the metastable phase was achieved owing to cation disorder in the crystal structure.

A metastable antifluorite-type Li₅GaS₄ electrolyte prepared by a mechanochemical process exhibits the highest conductivity of 2.1 × 10⁻⁵ S cm⁻¹ at 25 °C, which is three orders of magnitude higher than that of the heated Li₅GaS₄ samples with the stable phase.     

Mechanochemical synthesis of air-stable hexagonal Li4SnS4-based solid electrolytes containing LiI and Li3PS4

Sulfide solid electrolytes with high ionic conductivity and high air stability must be developed for manufacturing sulfide all-solid-state batteries. Li₁₀GeP₂S₁₂-type and argyrodite-type solid electrolytes exhibit a high ionic conductivity of ∼10⁻² S cm⁻¹ at room temperature, while emitting toxic H₂S gas when exposed to air. We focused on hexagonal Li₄SnS₄ prepared by mechanochemical treatment because it comprises air-stable SnS₄ tetrahedra and shows higher ionic conductivity than orthorhombic Li₄SnS₄ prepared by solid-phase synthesis. Herein, to enhance the ionic conductivity of hexagonal Li₄SnS₄, LiI was added to Li₄SnS₄ by mechanochemical treatment. The ionic conductivity of 0.43LiI·0.57Li₄SnS₄ increased by 3.6 times compared with that of Li₄SnS₄. XRD patterns of Li₄SnS₄ with LiI showed peak-shifting to lower angles, indicating that introduction of I⁻, which has a large ionic radius, expanded the Li conduction paths. Furthermore, Li₃PS₄, which is the most air-stable in the Li₂S–P₂S₅ system and has higher ionic conductivity than Li₄SnS₄, was added to the LiI–Li₄SnS₄ system. We found that 0.37LiI·0.25Li₃PS₄·0.38Li₄SnS₄ sintered at 200 °C showed the highest ionic conductivity of 5.5 × 10⁻⁴ S cm⁻¹ at 30 °C in the hexagonal Li₄SnS₄-based solid electrolytes. The rate performance of an all-solid-state battery using 0.37LiI·0.25Li₃PS₄·0.38Li₄SnS₄ heated at 200 °C was higher than those obtained using Li₄SnS₄ and 0.43LiI·0.57Li₄SnS₄. In addition, it exhibited similar air stability to Li₄SnS₄ by formation of LiI·3H₂O in air. Therefore, addition of LiI and Li₃PS₄ to hexagonal Li₄SnS₄ by mechanochemical treatment is an effective way to enhance ionic conductivity without decreasing the air stability of Li₄SnS₄.

Addition of LiI and Li₃PS₄ to hexagonal Li₄SnS₄ enhances ionic conductivity without decreasing the air stability of Li₄SnS₄.     

Garnet to hydrogarnet: effect of post synthesis treatment on cation substituted LLZO solid electrolyte and its effect on Li ion conductivity

We investigated why commercial Li₇La₃Zr₂O₁₂ (LLZO) with Nb- and Ta substitution shows very low mobility on a local scale, as observed with temperature-dependent NMR techniques, compared to Al and W substituted samples, although impedance spectroscopy on sintered pellets suggests something else: conductivity values do not show a strong dependence on the type of substituting cation. We observed that mechanical treatment of these materials causes a symmetry reduction from garnet to hydrogarnet structure. To understand the impact of this lower symmetric structure in detail and its effect on the Li ion conductivity, neutron powder diffraction and ⁶Li NMR were utilized. Despite the finding that, in some materials, disorder can be beneficial with respect to ionic conductivity, pulsed-field gradient NMR measurements of the long-range transport indicate a higher Li⁺ diffusion barrier in the lower symmetric hydrogarnet structure. The symmetry reduction can be reversed back to the higher symmetric garnet structure by annealing at 1100 °C. This unintended phase transition and thus a reduction in conductivity is crucial for the processing of LLZO materials in the fabrication of all-solid state batteries.

Investigation of commercial Li₇La₃Zr₂O₁₂ (LLZO) with various substituents. Although impedance spectroscopy suggests something else: the ion conductivity does not show a strong dependence on the substituting cation, but rather on the sample treatment.     

Mechanistic insight into the self-coupling of 5-hydroxymethyl furfural to C12 fuel intermediate catalyzed by ionic liquids

DFT calculations have been carried out to obtain insight into the self-coupling of biomass-based 5-hydroxymethyl furfural (HMF) to C₁₂ fuel intermediate 5,5′-dihydroxymethyl furoin (DHMF) catalyzed by ionic liquids (ILs). It was found that acetate-based IL or thiazolium IL in combination with the additive Et₃N show high catalytic performance, wherein N-heterocyclic carbons (NHCs) derived from the cations of ILs act as the nucleophiles and the protonated acetate anion or the [Et₃NH]⁺ acts as the proton shuttle. The effectiveness of this catalysis is attributed to the proton-shared three-center-four-electron (3c-4e) bonds between HMF and HOAc or [Et₃NH]⁺, which stabilize the transition states and the intermediates. In addition, the results of the calculations also confirm that the nucleophilicity and basicity of NHCs are key factors for the self-coupling reaction. These results rationalize the experimental findings and offer valuable insights into understanding the catalysis of ILs.

The self-coupling of HMF to DHMF catalyzed by ionic liquids has been rationalized well by performing DFT calculations.     

Mechanistic insight into mineral carbonation and utilization in cement-based materials at solid–liquid interfaces

In order to ensure the viability of CO₂ mineralization and utilization using alkaline solid waste, a mechanistic understanding of reactions at mineral–water interfaces was required to control the reaction pathways and kinetics. In this study, we provided new information for understanding the reactions of CO₂ mineralization and utilization at mineral–water interfaces. Here we have carried out high-energy synchrotron X-ray analyses to characterize the changes of mineral phases in petroleum coke fly ash during CO₂ mineralization and their subsequent utilization as supplementary cementitious materials in cement mortars. The 2-D synchrotron patterns were converted to 1-D diffraction patterns and the results were then interpreted via the Rietveld refinement. The results indicated that there was a continuous source of calcium ions mainly due to the dissolution of CaO and Ca(OH)₂ in fly ash. This would actually enhance the driving force of saturation index at the solid–fluid interfacial layer, and then could eventually result in the nucleation and growth of calcium carbonate (calcite) at the interface. A small quantity of CaSO₄ (anhydrite) in fly ash was also dissolved and simultaneously converted into calcite. In addition, the calcium sulfate in fly ash would effectively prevent the early hydration of tricalcium aluminate in blended cement, and thus could avoid the negative impact on its strength development. The proposed reaction mechanisms were also qualitatively verified by X-ray fluorescence mapping and electron microscopy. These results would help to design efficient reactors and cost-effective processes for CO₂ mineralization and utilization in the future.

Synchrotron-based X-ray analyses for understanding the reactions at mineral–water interfaces for CO₂ mineralization and utilization using petroleum coke fly ash.     

Mechanistic insight into the non-hydrolytic sol–gel process of tellurite glass films to attain a high transmission

The development of amorphous films with a wide transmission window and high refractive index is of growing significance due to the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films. High-index TeO₂-based glass films made via the sol–gel process are particularly suitable as their low temperature preparation process promises high compatibility with a large variety of nanoparticles and substrates that suffer from low thermal stability. However, due to the lack of in-depth understanding of the mechanisms of the formation of undesired metallic-Te (highly absorbing species) in the films, the preparation of high-transmission TeO₂-based sol–gel films has been severely hampered. Here, by gaining insight into the mechanistic chemistry of metallic-Te formation at different stages during the non-hydrolytic sol–gel process, we identify the chemical route to prevent the generation of metallic-Te in a TeO₂-based film. The as-prepared TeO₂-based film exhibits a high transmission that is close to the theoretical limit. This opens up a new avenue for advancing the performance of hybrid optoelectronic films via incorporating a large variety of unique nanoparticles.

This work develops a high-transparency amorphous film with a wide transmission window and high refractive index, which can potentially meet the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films.     

Roles of gel polymer electrolytes for high-power activated carbon supercapacitors: ion reservoir and binder-like effects

Ion reservoir and binder-like effects of gel polymer electrolytes (GPEs) are suggested for working mechanisms to enhance rate capability and cycling stability of activated carbon (AC) supercapacitors (SCs) even at 3.4 V. Analysis on kinetics from cyclic voltammetry, electrochemical reactions through in situ Fourier-transform infrared spectroscopy, and differential information of galvanostatic curves reveals that the increased rate-capability is derived dominantly by an improved non-faradaic process by the ion reservoir effect of GPEs in the AC. Although the designed GPEs induce slightly higher bulk and diffusion resistance at the incipient stage, the GPEs play a binder-like function to suppress detachment of AC particles and aggravation of impedance parameters during cycling at 3.4 V.

Roles of gel polymer electrolytes (GPEs), ion reservoir and binder-like effects, are suggested for enhanced rate capability and high durability of supercapacitors at 3.4 V, surpassing the conventional liquid SCs.     

Mechanistic insight into the photodynamic effect mediated by porphyrin-fullerene C60 dyads in solution and in Staphylococcus aureus cells

The photodynamic action mechanism sensitized by a non-charged porphyrin-fullerene C₆₀ dyad (TCP-C₆₀) and its tetracationic analogue (TCP-C₆₀⁴⁺) was investigated in solution and in Staphylococcus aureus cells. The ability of both dyads to form a photoinduced charge-separated state was evidenced by the reduction of methyl viologen in N,N-dimethylformamide (DMF). Moreover, the formation of superoxide anion radicals induced by these dyads was detected by the reduction of nitro blue tetrazolium. Also, photosensitized decomposition of l-tryptophan (Trp) was investigated in the presence of reactive oxygen species (ROS) scavengers. The addition of β-carotene and sodium azide had a slight effect on reaction rate. However, photooxidation of Trp mediated by TCP-C₆₀ was negligible in the presence of d-mannitol, while no protection was found using TCP-C₆₀⁴⁺. In a polar medium, these dyads mainly act by a contribution of type I pathway with low generation of singlet molecular oxygen, O₂(¹Δ_g). In S. aureus cell suspensions, an aerobic atmosphere was required for the photokilling of this bacterium. The photocytotoxicity induced by TCP-C₆₀ was increased in D₂O with respect to water, while a small effect was found using TCP-C₆₀⁴⁺. Furthermore, photoinactivation of microbial cells was negligible in the presence of sodium azide. The addition of d-mannitol did not affect the photoinactivation induced by TCP-C₆₀. In contrast, S. aureus cells were protected by d-mannitol when TCP-C₆₀⁴⁺ was used as a photosensitizer. Also, generation of O₂(¹Δ_g) in the S. aureus cells was higher for TCP-C₆₀ than TCP-C₆₀⁴⁺. Therefore, TCP-C₆₀ appears to act in microbial cells mainly through the mediation of O₂(¹Δ_g). Although, a contribution of the type I mechanism was found for cell death induced by TCP-C₆₀⁴⁺. Therefore, these dyads with high capacity to produce photoinduced charge-separated state represent interesting photosensitizers to inactivate microorganisms by type I or type II mechanisms. In particular, TCP-C₆₀ may be located in a non-polar microenvironment in the cells favoring a type II pathway, while a contribution of the type I mechanism was produced using the cationic TCP-C₆₀⁴⁺.

The photodynamic action mechanism sensitized by a non-charged porphyrin-fullerene C₆₀ dyad and its tetracationic analogue was investigated in solution and in Staphylococcus aureus cells.     

High ion conductivity based on a polyurethane composite solid electrolyte for all-solid-state lithium batteries

Solid polymer electrolytes (SPE) are considered a key material in all-solid Li-ion batteries (SLIBs). However, the poor ion conductivity at room temperature limits its practical applications. In this work, a new composite polymer solid electrolyte based on polyurethane (PU)/LiTFSI–Al₂O₃–LiOH materials is proposed. By adding a few inert fillers (Al₂O₃) and active agents (LiOH) into the PU/LiTFSI system, the ion conductivity of the SPE reaches 2 × 10⁻³ S cm⁻¹ at room temperature. Exploiting LiFePO₄ (LFP)‖Li as electrodes, the PU-based composite lithium battery is prepared. The experimental result shows that the LFP|SPE|Li displays high specific discharge capacity. The first specific discharge capacities at 0.2C, 0.5C, 1C and 3C are 159.6, 126, 110 and 90.1 mA h g⁻¹ respectively, and the Coulomb efficiency is found to be stable in the region of 92–99% which also shows a desirable cyclic stability after 150 cycles.

Adding inert filler to reduce the coupling effect of functional groups to Li⁺ and modifying the functional groups to reduce the adsorption of Li⁺ can lead to high ionic conductivity.     

Mechanistic insights into the improved properties of mayonnaise from the changes in protein structures of enzymatic modification-treated egg yolk

Heat treatment is an important step in mayonnaise production but can affect the quality of mayonnaise because thermal treatment can accelerate oil droplet coalescence. To resolve this issue, in this study, enzymatically modified egg yolks were applied to produce mayonnaise. Egg yolk hydrolyzed with 0.2% neutral protease could effectively produce mayonnaise with superior heat stability, and this effect was attributed to enzymatic modifications that increased the degree of amino acid ionization, the overall hydrophilicity and the ability to adsorb proteins. Moreover, electrophoresis and FT-IR results showed that the enzymatically modified egg yolk proteins had a smaller molecular weight and more flexible structure, which could also favor the improved properties. The study elucidated why mayonnaise prepared by enzymatic modification-treated egg yolk has better thermal stability.

Heat treatment is an important step in mayonnaise production but can affect the quality of mayonnaise because thermal treatment can accelerate oil droplet coalescence.     

An improved method for the incorporation of fluoromethyl ketones into solid phase peptide synthesis techniques

An improved and expedient technique for the synthesis of peptidyl-fluoromethyl ketones is described. The methodology is based on prior coupling of an aspartate fluoromethyl ketone to a linker and mounting it onto resin-bound methylbenzhydrylamine hydrochloride. Subsequently, by utilising standard Fmoc peptide procedures, a number of short Z-protected peptides were synthesised and assessed as possible inhibitors of the main protease from SARS-CoV-2 (3CL^pro).

An improved and expedient technique for the synthesis of peptidyl-fluoromethyl ketones is described.     

Understanding the ionic activity and conductivity value differences between random copolymer electrolytes and block copolymer electrolytes of the same chemistry

Herein, a systematic study where the macromolecular architectures of poly(styrene-block-2-vinyl pyridine) block copolymer electrolytes (BCE) are varied and their activity coefficients and ionic conductivities are compared and rationalized versus a random copolymer electrolyte (RCE) of the same repeat unit chemistry. By performing quartz crystal microbalance, ion-sorption, and ionic conductivity measurements of the thin film copolymer electrolytes, it is found that the RCE has higher ionic activity coefficients. This observation is ascribed to the fact that the ionic groups in the RCE are more spaced out, reducing the overall chain charge density. However, the ionic conductivity of the BCE is 50% higher and 17% higher after the conductivity is normalized by their ion exchange capacity values on a volumetric basis. This is attributed to the presence of percolated pathways in the BCE. To complement the experimental findings, molecular dynamics (MD) simulations showed that the BCE has larger water cluster sizes, rotational dynamics, and diffusion coefficients, which are contributing factors to the higher ionic conductivity of the BCE variant. The findings herein motivate the design of new polymer electrolyte chemistries that exploit the advantages of both RCEs and BCEs.

Random copolymer electrolytes have better permselectivity but lower ionic conductivity than block copolymer electrolytes of the same repeat unit chemistry.     

Deciphering the lithium ion movement in lithium ion batteries: determination of the isotopic abundances of 6Li and 7Li

Lithium ion batteries (LIBs) are the energy storage technology of choice in the context of renewable energies and electro-mobility. It is imperative to get a thorough understanding of the aging mechanisms to achieve a prolonged cycle and calendar life. One major drawback of the technology is continuous capacity fading during operation, which is partly attributed to the loss of active lithium, the object of this work''s analysis. While lithium ion battery aging is an intensively researched topic, there is still the need to determine the origin of the lost lithium and the lithium migration into the different cell components over time. To achieve this goal, different plasma-based mass spectrometric techniques in combination with isotope analysis are applied to obtain bulk as well as depth-resolved information about lithium ion movement and distribution of lithium in aged LIB cells. Different aging experiments are performed on NCM622/graphite cells with a ⁶Li-enriched electrolyte with subsequent Li analysis of the cell components. The results show that the charging rate, as well as the cycle number, has an impact on the ⁶Li/⁷Li-abundances and that the overall abundances show a rapid mixing of the isotopic species already after the first charge/discharge cycle for all cell components.

Different aging experiments were performed on NMC622/graphite cells with a ⁶Li enriched electrolyte to unravel the lithium distribution.     

Mechanistic insight into the catalytic hydrogenation of nonactivated aldehydes with a Hantzsch ester in the presence of a series of organoboranes: NMR and DFT studies

Mechanistic studies on the organoborane-catalyzed transfer hydrogenation of nonactivated aldehydes with a Hantzsch ester (diethyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate) as a synthetic NADH analogue were performed by NMR experiments and DFT calculations. In the reaction of benzaldehyde with the Hantzsch ester, the catalytic activity of tris[3,5-bis(trifluoromethyl)phenyl]borane was superior to that of other borane catalysts, such as tris(pentafluorophenyl)borane, trifluoroborane etherate, or triphenylborane. Stoichiometric NMR experiments demonstrated that the hydrogenation process proceeds through activation of the aldehyde by the borane catalyst, followed by hydride transfer from the Hantzsch ester to the resulting activated aldehyde. DFT calculations for the hydrogenation of benzaldehyde with the Hantzsch ester in the presence of borane catalysts supported the reaction pathway and showed why the catalytic activity of tris[3,5-bis(trifluoromethyl)phenyl]borane is higher than that of the other boron catalysts. Association constants and Gibbs free energies in the reaction of boron catalysts with benzaldehyde or benzyl alcohol, which were investigated by ¹H NMR analyses, also indicated why tris[3,5-bis(trifluoromethyl)phenyl]borane is a superior catalyst to tris(pentafluorophenyl)borane, trifluoroborane etherate, or triphenylborane in the hydrogenation reaction.

Mechanistic studies on the organoborane-catalyzed transfer hydrogenation of nonactivated aldehydes with a Hantzsch ester as a synthetic NADPH analogue were performed by NMR experiments and DFT calculations.     

Mechanistic insight into B(C6F5)3 catalyzed imine reduction with PhSiH3 under stoichiometric water conditions

A DFT and experimental study on the mechanism of B(C₆F₅)₃ catalyzed imine reduction is performed using PhSiH₃ as reductant under stoichiometric water conditions. Ingleson’s path B is reconfirmed here. And four novel (C₆F₅)₃B–OH₂ induced pathways (paths C2, C3, D2 and D3) entirely different from all the previous mechanisms were determined for the first time. They are all B(C₆F₅)₃ and water/amine catalyzed cycles, in which the nucleophilic water or amine catalyzed addition step between PhSiH₃ and the N-silicon amine cation is the rate-determining step of paths C2/D2 and C3/D3 with activation Gibbs free energy barriers of 23.9 and 18.3 kcal mol⁻¹ in chloroform, respectively, while the final desilylation of the N-silicon amine cation depends on an important intermediate, (C₆F₅)₃B–OH⁻. The competitive behavior of the 5 paths can explain the experimental facts perfectly; if all the reactants and catalysts are added into the system simultaneously, water amount and nucleophiles (excess water and produced/added amine) provide on–off selectivity of the pathways and products. 1 eq. water leads to quick formation of (C₆F₅)₃B–OH⁻, leading to B-II being turned off, and nucleophiles like excess water and produced/added amine switch on CD-II, leading to production of the amine. B-I′ of Ingleson’s path B is the only mechanism for anhydrous systems, giving N-silicon amine production only; B-I and C-I are competitive paths for systems with no more than 1 eq. water, producing the N-silicon amine and the [PhHC NHPh]⁺[(C₆F₅)₃B–OH]⁻ ion pair; and paths C2, C3, D2 and D3 are competitive for systems with 1 eq. water and nucleophiles like excess water or added/produced amine, directly giving amination products.

Hydrosilylation or amination products? It depends on water amount and nucleophiles like excess water or produced/added amines.