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The synthesis and decomposition of formic acid (FA) in aqueous triethylamine (NEt3) with solid molecular phosphine catalysts is demonstrated.

Electrochemical water splitting is a process to store renewable energy in hydrogen, which is a green energy carrier producing only water when combusted. However, the overall electrochemical water splitting is limited by the low efficiency of the anodic oxygen evolution reaction (OER) leading to a high overpotential. In this study, finely dispersed cobalt particles supported on graphene are prepared as an anodic catalyst and coupled with phosphate activation to enhance and stabilize OER activity. The small particles enable a high exposure of the surface active sites. Also, the highly conductive graphene backbone accelerates electron transport. Activation by phosphate in the electrolyte leads to the formation of the active Co(iii) species with enriched oxygen vacancies meanwhile facilitating the kinetics. The finely dispersed cobalt particles supported on graphene together with phosphate activation lead to high electrochemical surface area and intrinsic activity, achieving a current density of 10 mA cm−2at an overpotential of 0.35 V and a low Tafel slope of 45 mV per decade, together with good stability. The cobalt mass based current density is 19-8000 times higher than current benchmarking catalysts.

Stabilization of single metal atoms is a persistent challenge in heterogeneous catalysis. Especially supported late transitions metals are prone to undergo agglomeration to nanoparticles under reducing conditions. In this study, nitrogen-rich covalent triazine frameworks (CTFs) are used to immobilize iridium complexes. Upon reduction at 400°C, immobilized Ir(acac)(COD) on CTF does not form nanoparticles but transforms into a highly active Ir single atom catalyst. The resulting catalyst systems outperforms both the immobilized complex and supported nanoparticles in the dehydrogenation of formic acid as probe reaction. This superior performance could be traced back to decisive changes of the coordination geometry positively influencing activity, selectivity and stability. Spectroscopic analysis reveals an increase of electron density on the cationic iridium site by donation from the CTF macroligand after removal of the organic ligand sphere from the Ir(acac)(COD) precursor complex upon reductive treatment. This work demonstrates the ability of nitrogen moieties to stabilize molecular metal species against agglomeration and opens avenues for catalysts design using isolated sites in high-temperature applications under reducing atmosphere.

Advanced functional materials x, 2203520 - (2022). doi:10.1002/adfm.202203520, Water splitting is an environmentally friendly strategy to produce hydrogen but is limited by the oxygen evolution reaction (OER). Therefore, there is an urgent need to develop highly efficient electrocatalysts. Here, NiFe layered double hydroxides (NiFe LDH) with tunable Ni/Fe composition exhibit corresponding dependent morphology, layered structure, and chemical states, leading to higher activity and better stability than that of conventional NiFe LDH-based catalysts. The characterization data show that the low overpotentials (249 mV at 10 mA cm–2), ultrasmall Tafel slopes (24 mV dec–1), and high current densities of Ni3Fe LDH result from the larger fraction of trivalent Fe3+ and the optimized local chemical environment with more oxygen coordination and ordered atomic structure for the metal site. Owing to the active intermediate species, Ni(Fe)OOH, under OER conditions and a reversible dynamic phase transition during the cycling process, the Ni3Fe LDH achieves a high current density of over 2 A cm–2 at 2.0 V, and durability of 400 h at 1 A cm–2 in a single cell test. This work provides insights into the relationship between the composition, electronic structure of the layer, and electrocatalytic performance, and offers a scalable and efficient strategy for developing promising catalysts to support the development of the future hydrogen economy., Published by Wiley-VCH, Weinheim

Methyl formate was produced in one pot through the hydrogenation of CO2 to formic acid/formate followed by an esterification step. The route offers the possibility to integrate renewable energy into the fossil-based chemical value chain. In this work, a phosphine-polymer-anchored Ru complex was shown to be an efficient solid catalyst for the direct hydrogenation of CO2 to methyl formate. The 1,2-bis(diphenylphosphino)ethane-like polymer presented the highest activity with a turnover number (TON) of up to 3401 at 160 °C. The reaction parameters were systemically investigated to optimize the reaction towards the formation of methyl formate. This catalyst could be reused seven times without a significant decrease in activity. Evolution of the catalytic Ru center during the reaction was revealed, and a possible reaction mechanism was proposed.

Low-cost, highly active, and highly stable catalysts are desired for the generation of hydrogen and oxygen using water electrolyzers. To enhance the kinetics of the oxygen evolution reaction in an acidic medium, it is of paramount importance to redesign iridium electrocatalysts into novel structures with organized morphology and high surface area. Here, we report on the designing of a well-defined and highly active hollow nanoframe based on iridium. The synthesis strategy was to control the shape of nickel nanostructures on which iridium nanoparticles will grow. After the growth of iridium on the surface, the next step was to etch the nickel core to form the NiIr hollow nanoframe. The etching procedure was found to be significant in controlling the hydroxide species on the iridium surface and by that affecting the performance. The catalytic performance of the NiIr hollow nanoframe was studied for oxygen evolution reaction and shows 29 times increased iridium mass activity compared to commercially available iridium-based catalysts. Our study provides novel insights to control the fabrication of iridium-shaped catalysts using 3d transition metal as a template and via a facile etching step to steer the formation of hydroxide species on the surface. These findings shall aid the community to finally create stable iridium alloys for polymer electrolyte membrane water electrolyzers, and the strategy is also useful for many other electrochemical devices such as batteries, fuel cells, sensors, and solar organic cells.

The development of improved catalysts for highly selective hydrogenation of nitroarenes is described. For this purpose Co nanoparticles were supported on ordered mesoporous carbon CMK-3 and characterized in detail. The optimal CMK-3-CoPc catalyst exhibits excellent hydrogenation activity for several (hetero)aromatic nitro compounds and yielded the corresponding anilines under mild conditions (40 °C, 20 bar H2).

In this work the effect of multivalency on the stability of NIR-absorbing HAuNSs and AuNRs functionalized by mono-, bi- and tridentate polyethyleneglycol (PEG) thiol ligands is reported. Comparison of commercially-available monodentate and self-synthesized bi- and tridentate methoxy terminated thiol-polyethyleneglycol ligands having molecular weights of around 5000 Da shows the stability increase of HAuNSs and AuNRs for bi- and tridentate ligands, attributed to the multivalency of the ligands. The stability was explored according to three different aspects: (1) stability towards competition reactions with the strong binding ligand dithiothreitol, (2) resistance towards oxidative Au dissolution with potassium cyanide, and (3) colloidal stability, tested by the addition of NaCl. Our PEGylation approach leads to AuNRs where the CTAB concentration is below the detection limit of the performed analytical methods, which is vital for any clinical applications. Furthermore, we found strikingly high biocompatibility after PEGylation for both particle types whereby we observed no significant difference in cytotoxicity comparing the mono-, bi- and tridentate PEGylated species.

Formic acid is a promising hydrogen storage medium and can be produced by catalytic hydrogenation of CO2 . Molecular ruthenium complexes immobilized on phosphine polymers have been found to exhibit excellent productivity and selectivity in the catalytic hydrogenation of CO2 under mild conditions. The polymeric analog of 1,2-bis(diphenylphosphino)ethane exhibited the highest activity and turnover numbers up to 13 170 were obtained in a single run. This catalyst was already active at 40 °C and with a catalyst loading of only 0.0006 mol %. Recycling experiments revealed a loss of activity after the first run, followed by a gradual decrease during the subsequent runs. This is attributed to a change in the catalytically active complex during the hydrogenation reaction. High selectivity towards formate and low leaching were maintained in the absence of CO formation. Based on the catalyst characterization, a mechanism for the CO2 hydrogenation is proposed.

Composite materials of polyacrylonitrile and carbon nanotubes in varying amounts were synthesised as metal-free catalysts for the oxygen evolution reaction. For the best material possessing 12.8% CNT a low overpotential of 368 mV at 10 mA cm−2 in 1 M KOH, high normalised activity and exchange current density were obtained. A good balance between conductivity and hydrophilicity proved essential for an efficient reaction.

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Methyl formate was produced in one pot through the hydrogenation of CO

To proceed the miniaturization of electronic devices new materials and new device designs are needed. A promising candidate for future gate dielectrics are ternary rare earth oxides which exhibit permittivities up to 40. Such amorphous oxides (e.g. GdScO3 and LaLuO3) were introduced in silicon based MOSFETs and showed good performance according electron and hole mobility or steep subthreshold slopes down to 65 mV/dec [1-3]. They are also used in SiGe or Ge based devices with the same good performance [4]. The ternary rare earth oxides GdScO3 (GSO) and LaLuO3 (LLO) are deposited epitaxial and amorphous by PLD on α-GaN deposited by MOVPE on sapphire (Al2O3) substrates c.f. Hardtdegen et al. [5] and Y2O3 deposited on Si(111) by molecular beam epitaxy analogous to the approach of Tarnawska et al. [6] at different temperatures. Depending on the growth temperatures and the substratethe amorphous, orthorhombic, hexagonal or cubic phase is formed. On GaN GSO grows hexagonal proofed by a Θ-2Θ scan exhibiting beside the peaks of GaN and sapphire two peaks corresponding to the reflections of (0002) and (0004) hexagonal GSO (Figure 1). Furthermore the hexagonal structure was confirmed by TEM and the lattice constants determined from the diffraction pattern are a=0.36 nm and c=0.58 nm. The layers were electrical characterized by CV measurements using Al pads as top electrode. CET plots were made with different layer thicknesses and the permittivity (k) was extracted from inverses of the slope of the fitted lines. The k of hexagonal GSO on GaN is 27. Furthermore GSO was grown on Y2O3. Depending on the thickness of Y2O3 GSO grows hexagonal on 1 nm layers and cubic on 7 nm layers. Hexagonal GSO and cubic GSO deposited on Y2O3 on Si exhibit a k of 24 and 14, respectively. LLO was grown on GaN and exhibits a hexagonal structure at a growth temperature of 600°C and cubic structure at 900 °C The transition temperature seems to be 860 °C at which the cubic and the hexagonal crystal structure both are present. The rocking curve displays a FWHM of 0.15° for the hexagonal and the cubic structure. The lattice constants measured by XRD of the hexagonal and the cubic crystal structure are a=0.375 nm, c=0.612 nm and a=1.086 nm, respectively. Also on the Y2O3 LLO grows epitaxial. At low temperatures the hexagonal structure and high temperatures the cubic structure forms, too. The lattice constants determined by XRD and TEM are a=0.375 nm and c=0.612 nm for the hexagonal structure and a=1.086 nm for the cubic structure. LLO exhibits a k of 26 and 23 for hexagonal LLO and cubic LLO on Y2O3on Si, respectively. Finally we will present our recent results about GSO and LLO deposited by PLD especially the crystal structure and the electrical properties. Therefore we will show the dependence of the material properties to the growth conditions. References 1. E. Durgun Özben, J.M.J.L., A. Nichau, M. Schnee, S. Lenk, A. Besmehn, K. K. Bourdelle, and J.S. Q. T. Zhao, and S. Mantl, Integration of LaLuO3( k∼30) as High- k Dielectric on Strained and Unstrained SOI MOSFETs With a Replacement Gate Process. IEEE ELECTRON DEVICE LETTERS,, 2011. 32: p. 15-17. 2. Lopes, J.M.J., et al., Amorphous ternary rare-earth gate oxides for future integration in MOSFETs. Microelectronic Engineering, 2009. 86(7-9): p. 1646-1649. 3. Roeckerath, M., et al., Gadolinium scandate as an alternative gate dielectric in field effect transistors on conventional and strained silicon. Applied Physics A, 2009. 94(3): p. 521-524. 4. Minamisawa, R.A., et al., High mobility strained Si0.5Ge0.5/SSOI short channel field effect transistors with TiN/GdScO3 gate stack. Microelectronic Engineering, 2011. 88(9): p. 2955-2958. 5. Hardtdegen, H., et al., Uniform III-nitride growth in single wafer horizontal MOVPE reactors. physica status solidi (a), 2005. 202(5): p. 744-748. 6. Tarnawska, L., et al., Single crystalline Sc2O3/Y2O3 heterostructures as novel engineered buffer approach for GaN integration on Si (111). Journal of Applied Physics, 2010. 108(6): p. 063502. Figure 1

Formic acid is a promising hydrogen storage medium and can be produced by catalytic hydrogenation of CO