Electrocatalytic water oxidation by CuII complexes with branched peptides

Two mononuclear CuII complexes with tetrapeptides incorporating a L-2,3-diaminopropionic acid (dap) branching unit are reported to undergo PCET and catalyse water oxidation. C-terminal His extension of dap (L = 2GH) instead of Gly (L = 3G) lowers the pKa for CuIIIH-2L (9.36 vs. 9.98) and improves the TOF at pH 11 (53 vs. 24 s-1)

Bimetallic Ag–Au/SiO2 catalysts: Formation, structure and synergistic activity in glucose oxidation

SiO2 supported Ag–Au bimetallic catalysts were prepared by sol adsorption method with 10/90, 20/80, 33/67, and 50/50 Ag/Au molar ratios. Reduction of HAuCl4 in Ag sol resulted in alloyed Ag–Au colloid particles and that structure remained after calcination and reduction treatment. The alloy structure of the catalysts was confirmed by UV–visible spectroscopy and high resolution transmission electron microscopy. The Au–Ag bimetallic effect and its dependence on the Ag/Au molar ratio was studied in glucose oxidation where synergistic activity increase was observed compared to the Au/SiO2 reference sample in the case of the bimetallic samples with less than Ag/Au = 50/50 molar ratio. The Ag/SiO2 was inactive at the same conditions. The Ag/Au surface atomic ratios – calculated by X-ray photoelectron spectroscopy (XPS) – were slightly higher than in the bulk—determined by prompt gamma activation analysis (PGAA). The higher activity of the bimetallic samples is suggested to be caused by the improved O2 activating ability provided by Ag sites. The further increase of Ag loading above the optimal concentration may dilute or cover the Au to such an extent that the number of gold ensembles necessary for glucose activation decreases deteriorating the activity

Na-promoted Ni/ZrO2 dry reforming catalyst with high efficiency: details of Na2O-ZrO2-Ni interaction controlling activity and coke formation

Herein, a 0.6 wt% Na-promoted 3% Ni/ZrO2 dry reforming catalyst and its unpromoted counterpart are discussed in detail. Structural investigations were carried out using TEM, TPR, XRD, XPS, and CO pulse chemisorption followed by TPD and DRIFTS methods. In the presence of a dry reforming mixture, bidentate carbonates were detected on Na-promoted Ni/ZrO2, while on Ni/ZrO2 effective hydrogenation by metallic Ni converted bicarbonates to formate species. In continuous flow atmospheric catalytic tests in a high excess of methane, a reactive-type coke was formed on the promoted sample, which did not cause significant deactivation. Temperature ramped 13CO2 isotope labeled dry reforming experiments in a closed loop sub-atmospheric circulation system revealed 13CH4 formation on Ni/ZrO2, while in the case of the promoted catalyst methanation was retarded until the complete consumption of oxidants (from 13CO2). In isothermal experiments in the same circulation system carbon monoxide disproportionation was observed on Ni/ZrO2 leaving carbon on Ni, besides the coke formed from the CH4 source, while on the promoted catalyst carbonaceous deposit under the same conditions did not form from CH4. The superb catalytic properties of Na-promoted Ni/ZrO2 are explained by a proposed catalytic cycle compiling the dynamic participation (formation and decomposition) of the surface Na2CO3 or NaHCO3 species surrounding the NiOxHy active sites on a ZrO2 support that is able to accommodate the labile Na2O promoter capturing and releasing CO2 oxidant

Synthesis and characterization of novel Ru(II)-diimine complexes for combination of layered double hydroxides

Conversion of solar energy into chemical energy by using stable and efficient photosynthetic devices is a key and timely challenge. Molecular hydrogen, as a promising substitute for fossil fuels, makes the water splitting a prominently important catalytic process. In the past decades the number of studies on the photochemistry of diimine-type Ru(II) complexes has extremely increased. These compounds can be dissolved in a variety of solvents by careful choice of the appropriate counter ion or ligand modifications. They also have a broad and intense metal-to-ligand charge transfer (MLCT) band in the visible region with a tunable maximum typically around 400 and 500 nm. The redox and excited-state properties can be tuned by the alteration of the ligands or ligand substituents. In practice, the bipyridine-type Ru(II) complexes as photosensitizers, can be part of photocatalytic molecular devices. Moreover, using layered double hydroxides (LDHs) as substrate, a novel hybrid photosensitized system can be obtained. Novel Ru-complexes with diimine ligands and their organic-inorganic nanohybrid forms are characterized by UV-visible spectroscopy, spectrofluorometry, secondary ion mass spectrometry (SIMS), fourier transform infrared spectroscopy (FT-IR). For the electroanalytical measurements, a potentiostat and cyclic voltammetry will be used. Acknowledgement This project was supported by the János Bolyai research scholarship of HAS for József S. Pap