Reactions of (-)-sparteine with alkali metal HMDS complexes : conventional meets the unconventional

Conventional (-)-sparteine adducts of lithium and sodium 1,1,1,3,3,3-hexamethyldisilazide (HMDS) were prepared and characterised, along with an unexpected and unconventional hydroxyl-incorporated sodium sodiate, [(-)-sparteine·Na(-HMDS)Na·(-)-sparteine]+[Na4(-HMDS)4(OH)]--the complex anion of which is the first inverse crown ether anion

From a Molecular Single-Source Precursor to a Selective High- Performance RhMnOx Catalyst for the Conversion of Syngas to Ethanol

The first carbonyl RhMn cluster Na2[Rh3Mn3(CO)18] 2 has been synthesized and structurally characterized, resulting from the salt metathesis reaction of RhCl3 with Na[Mn(CO)5] 1 in 49% isolated yield. The dianionic Rh3Mn3 cluster core of 2 can serve as a molecular single‐source precursor (SSP) for the low temperature preparation of selective high‐performance RhMn catalysts for the conversion of syngas to ethanol (StE). Impregnation of 2 on silica (davisil) led to three different silica‐supported RhMnOx catalysts with dispersed Rh nanoparticles tightly surrounded by a MnOx matrix. With ethanol selectivities of up to 24.1%, the Rh3Mn3 cluster precursor‐derived catalysts show the highest reported selectivity and performance in the conversion of StE for silica‐supported RhMnOx catalysts

The Pivotal Role of s , p , and f Block Metals in Water Electrolysis Status Quo and Perspectives

Transition metals, in particular noble metals, are the most common species in metal mediated water electrolysis because they serve as highly active catalytic sites. In many cases, the presence of nontransition metals, that is, s , p , and f block metals with high natural abundance in the earth crust in the catalytic material is indispensable to boost efficiency and durability in water electrolysis. This is why alkali metals, alkaline earth metals, rare earth metals, lean metals, and metalloids receive growing interest in this research area. In spite of the pivotal role of these nontransition metals in tuning efficiency of water electrolysis, there is far more room for developments toward a knowledge based catalyst design. In this review, five classes of nontransition metals species which are successfully utilized in water electrolysis, with special emphasis on electronic structure catalytic activity relationships and phase stability, are discussed. Moreover, specific fundamental aspects on electrocatalysts for water electrolysis as well as a perspective on this research field are also addressed in this account. It is anticipated that this review can trigger a broader interest in using s , p , and f block metals species toward the discovery of advanced polymetal containing electrocatalysts for practical water splittin

Oxygen Evolution Activity of Amorphous Cobalt Oxyhydroxides Interconnecting Precatalyst Reconstruction, Long Range Order, Buffer Binding, Morphology, Mass Transport, and Operation Temperature

Nanocrystalline or amorphous cobalt oxyhydroxides CoCat are promising electrocatalysts for the oxygen evolution reaction OER . While having the same short range order, CoCat phases possess different electrocatalytic properties. This phenomenon is not conclusively understood, as multiple interdependent parameters affect the OER activity simultaneously. Herein, a layered cobalt borophosphate precatalyst, Co H2O 2[B2P2O8 OH 2] H2O, is fully reconstructed into two different CoCat phases. In contrast to previous reports, this reconstruction is not initiated at the surface but at the electrode substrate to catalyst interface. Ex situ and in situ investigations of the two borophosphate derived CoCats, as well as the prominent CoPi and CoBi identify differences in the Tafel slope range, buffer binding and content, long range order, number of accessible edge sites, redox activity, and morphology. Considering and interconnecting these aspects together with proton mass transport limitations, a comprehensive picture is provided explaining the different OER activities. The most decisive factors are the buffers used for reconstruction, the number of edge sites that are not inhibited by irreversibly bonded buffers, and the morphology. With this acquired knowledge, an optimized OER system is realized operating in near neutral potassium borate medium at 1.62 0.03 VRHE yielding 250 mA cm amp; 8722;2 at 65 C for 1 month without degrading performanc

An Intermetallic CaFe6Ge6 Approach to Unprecedented Ca Fe O Electrocatalyst for Efficient Alkaline Oxygen Evolution Reaction

Based on the low cost and relatively high catalytic activity, considerable efforts have been devoted towards developing redox active transition metal TM oxygen electrocatalysts for the alkaline oxygen evolution reaction OER while the role of redox inactive alkaline earth metals has often been neglected in OER. Herein, for the first time, we developed a novel ternary intermetallic CaFe6Ge6 precatalyst, whose surface rapidly transforms into a porous ultrathin Ca amp; 8722;Fe amp; 8722;O heteroshell structure during alkaline OER through the oxidative leaching of surficial Ge. Benefiting from synergistic effects, this highly efficient OER active material with distinct Ca amp; 8722;Fe amp; 8722;O layers has a large electrochemical surface area and more exposed active Fe sites than a Ca free FeOx phase. Also, the presence of Ca in Ca amp; 8722;Fe amp; 8722;O is responsible for the enhanced transport and activation of hydroxyls and related OER reaction intermediate as unequivocally illustrated by a combination of quasi in situ Raman spectroscopy and various ex situ method

In Situ Formed Sn1 xInx In1 ySnyOz Core Shell Nanoparticles as Electrocatalysts for CO2 Reduction to Formate

Electrochemical reduction of CO2 CO2RR driven by renewable energy has gained increasing attention for sustainable production of chemicals and fuels. Catalyst design to overcome large overpotentials and poor product selectivity remains however challenging. Sn SnOx and In InOx composites have been reported active for CO2RR with high selectivity toward formate formation. In this work, the CO2RR activity and selectivity of metal metal oxide composite nanoparticles formed by in situ reduction of bimetallic amorphous SnInOx thin films are investigated. It is shown that during CO2RR the amorphous SnInOx pre catalyst thin films are reduced in situ into Sn1 XInX In1 YSnYOz core shell nanoparticles composed of Sn rich SnIn alloy nanocores with x lt; 0.2 surrounded by InOx rich bimetallic InSnOx shells with 0.3 lt; y lt; 0.4 and z amp; 8776; 1 . The in situ formed particles catalyze the CO2RR to formate with high faradaic efficiency 80 and outstanding formate mass activity 437 A gIn Sn amp; 8722;1 amp; 8722;1.0 V vs RHE in 0.1 m KHCO3 . While extensive structural investigation during CO2RR reveals pronounced dynamics in terms of particle size, the core shell structure is observed for the different electrolysis conditions essayed, with high surface oxide contents favoring formate over hydrogen selectivit

Screening of Heterogeneous Photocatalysts for Water Splitting

In this contribution, a simple method for the screening of photocatalytic activity of catalyst materials is presented. The method is based on two steps the immobilization of the photocatalyst and the subsequent testing of their photocatalytic activity, using the gas evolution at the solid liquid interface. Up to four catalysts can be tested under the same conditions. The observed gas evolution for selected photocatalysts is consistent with trends reported in the literature from conventional photocatalytic reactor

Valence isomerization of 2-phospha-4-silabicyclo[1.1.0]butane: a high-level ab initio study

The rearrangements for 2-phospha-4-silabicyclo[1.1.0]butane, analogous to the valence isomerization of the hydrocarbons bicyclobutane, 1,3-butadiene, and cyclobutene, were studied at the (U)QCISD(T)/6-311+G**//(U)QCISD/6-31G* level of theory. The monocyclic 1,2-dihydro-1,2-phosphasiletes are shown to be the thermodynamically preferred product, in contrast to the isomerization of the hydrocarbons, which favors the 1,3-butadiene structure. Furthermore, an unprecedented direct isomerization pathway to the 1,2-dihydro-1,2-phosphasiletes was identified. This pathway is competitive with the isomerization via the open-chain butadienes and becomes favorable when electron-donating substituents are present on silicon