Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

The design and synthesis of efficient electrocatalysts are important for electrochemical conversion technologies. The oxygen evolution reaction (OER) is a key process in such conversions, having applications in water splitting and metal–air batteries. Here, we report ultrathin metal–organic frameworks (MOFs) as promising electrocatalysts for the OER in alkaline conditions. Our as-prepared ultrathin NiCo bimetal–organic framework nanosheets on glassy-carbon electrodes require an overpotential of 250 mV to achieve a current density of 10 mA cm−2. When the MOF nanosheets are loaded on copper foam, this decreases to 189 mV. We propose that the surface atoms in the ultrathin MOF sheets are coordinatively unsaturated—that is, they have open sites for adsorption—as evidenced by a suite of measurements, including X-ray spectroscopy and density-functional theory calculations. The findings suggest that the coordinatively unsaturated metal atoms are the dominating active centres and the coupling effect between Ni and Co metals is crucial for tuning the electrocatalytic activity. Efficient electrocatalysts for the oxygen–evolution reaction are desired due to their importance in applications such as water splitting and metal–air batteries. Here, the authors engineer ultrathin metal–organic frameworks that require low overpotential to generate oxygen from alkaline media.

Ultrathin metal–organic framework nanosheets for electrocatalytic oxygen evolution

ion from a primary OH group of glyc-erol. 223,231 A similar mechanism was proposed manyyears ago for alcohol oxidation on Pt/C, involving asecond step, the transfer of a hydride ion to the Ptsurface (Scheme 11). 8,87,237 We consider it more feasible that the rate-deter-mining step is the cleavage of the C-H bond at theR-carbon atom. A similar mechanism is now generallyaccepted for Au electrodes (Scheme 12). 238 Despite thestructural differences between Au nanoparticles andan extended Au electrode surface, there are alsosimilarities, such as the critical role of aqueousalkaline medium and the absence of deactivation dueto decomposition products (CO and C x H y frag-ments). 239,240 An important question is the nature of active siteson Au nanoparticles. Electrooxidation of ethanol onAu nanoparticles supported on glassy carbon re-quired the partial coverage of Au surface by oxides. 241 Another analogy might be the model proposed for COoxidation. 219,242,243 According to this suggestion, theactive site consists of an ensemble of metallic Auatoms and a cationic Au

Oxidation of Alcohols with Molecular Oxygen on Solid Catalysts

Mesoporous silica materials containing functionalized organic monolayers have been synthesized. Solid-state nuclear magnetic resonance suggests that a cross-linked monolayer of mercaptopropylsilane was covalently bound to mesoporous silica and closely packed on the surface. The relative surface coverage of the monolayers can be systematically varied up to 76 percent. These materials are extremely efficient in removing mercury and other heavy metals from both aqueous and nonaqueous waste streams, with distribution coefficients up to 340,000. The stability of these materials and the potential to regenerate and reuse them have also been demonstrated. The surface modification scheme reported here enables rational design of the surface properties of tailored porous materials and may lead to the synthesis of more sophisticated functionalized composites for environmental and industrial applications.

https://science.sciencemag.org/content/sci/276/5314/923.full.pdf

Functionalized Monolayers on Ordered Mesoporous Supports

Single-atom catalysts (SACs) have recently attracted broad research interest as they combine the merits of both homogeneous and heterogeneous catalysts. Rational design and synthesis of SACs are of immense significance but have so far been plagued by the lack of a definitive correlation between structure and catalytic properties. Here, we report a general approach to a series of monodispersed atomic transition metals (for example, Fe, Co, Ni) embedded in nitrogen-doped graphene with a common MN4C4 moiety, identified by systematic X-ray absorption fine structure analyses and direct transmission electron microscopy imaging. The unambiguous structure determination allows density functional theoretical prediction of MN4C4 moieties as efficient oxygen evolution catalysts with activities following the trend Ni > Co > Fe, which is confirmed by electrochemical measurements. Determination of atomistic structure and its correlation with catalytic properties represents a critical step towards the rational design and synthesis of precious or nonprecious SACs with exceptional atom utilization efficiency and catalytic activities.

General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

Theory of EXAFS. Theory of XANES. INSTRUMENTAL AND DATA ANALYSIS. Design of an EXAFS Experiment. EXAFS with Synchrotron Radiation. Laboratory EXAFS Facilities. Data Analysis. APPLICATIONS. Biochemical Application of X-ray Absorption Spectroscopy. Catalysis. Amorphous and Liquid Systems. SEXAFS. XANES Spectroscopy.

X-ray absorption : principles, applications, techniques of EXAFS, SEXAFS, and XANES

https://pure.tue.nl/ws/files/2325948/620870.pdf

Determination of metal particle size of highly dispersed Rh, Ir, and Pt catalysts by hydrogen chemisorption and EXAFS

https://pure.tue.nl/ws/files/1876217/620456.pdf

Raman spectroscopic study of Co-Mo/gamma-Al2O3 catalysts

An in situ cell suitable for transmission EXAFS measurements on catalytic samples is described. The cell can be used for catalyst pretreatments in various atmospheres (including H2, H2S, O2 and CO) in a temperature range upto 700 K. The sample is heated by conducting heat from an external heater to the sample. During measurement the samples can be cooled down to 77 K by conducting heat from the sample to an external liquid nitrogen container. During the pretreatment and the measurement a waterflow through the body of the cell keeps certain crucial parts from overheating or icing up. To avoid radiation leaks in powdery samples these samples are pressed in a selfsupporting wafer and held in a disk‐shaped sampleholder. Tests by various catalytic groups have proven the suitability of the design.

/pdf/an-in-situ-cell-for-transmission-exafs-measurements-on-25h787tf45.pdf

An in situ cell for transmission EXAFS measurements on catalytic samples

MgO-supported catalysts were prepared from [HRe(CO)5] and [H,Re3(CO),,] and characterized by extraction of surface
organometallics, infrared and ultraviolet/visible spectroscopy, and extended X-ray absorption fine structure (EXAFS)
spectroscopy. The EXAFS analysis and other data show that [H,Re,(CO),,] was initially deprotonated on the MgO surface,
giving a surface-bound anion with a structure comparable to that of the salt [Ph,As] [H2Re,(C0)12] and having a Re-Mg
distance of 2.39 8,. Heating of the supported cluster anion in helium to 225 OC led to oxidation and breakup of the cluster
framework, giving a mononuclear complex formulated as [Re(C0)3(0MgJ3(]w here the braces refer to groups terminating
the bulk oxide). The distances characterizing the bonding of the Re to the support are Re-O = 2.15 8, and Re-Mg = 2.80
8,. A Re-Re distance of 3.94 8, was observed, consistent with the decomposition of the cluster on the support to form ensembles
consisting of three of the Re subcarbonyls, for which a structural model is presented. Treatment of this sample in hydrogen
at 350 'C gave a Re species with oxygen neighbors at average distances of 1.94 and 2.45 8,. Heating of this sample to 500
OC in hydrogen led to reduction and conversion of most of the Re into metal crystallites. The several samples were tested
as catalysts, as described in a companion paper.

/pdf/surface-catalytic-sites-prepared-from-hre-co-5-and-h3re3-co-4mfpf6g8gh.pdf

DC Diek Koningsberger

Papers

X-ray absorption : principles, applications, techniques of EXAFS, SEXAFS, and XANES

Determination of metal particle size of highly dispersed Rh, Ir, and Pt catalysts by hydrogen chemisorption and EXAFS

Raman spectroscopic study of Co-Mo/gamma-Al2O3 catalysts

An in situ cell for transmission EXAFS measurements on catalytic samples

Surface catalytic sites prepared from [HRe(CO)5] and [H3Re3(CO)12]: mononuclear, trinuclear, and metallic rhenium catalysts supported on MgO