Improved electrocatalytic activity of Pt on carbon nanofibers for glucose oxidation mediated by support oxygen groups in Pt perimeter

Support effects in supported metal catalysts are well studied for thermocatalytic reactions, but less studied for electrocatalytic reactions. Here, we prepared a series of Pt supported on carbon nanofiber catalysts which vary in their Pt particle size and the content of oxygen groups on the surface of the CNF. We show that the activity of these catalysts for electrocatalytic glucose oxidation relates linearly with the content of support oxygen groups. Since the electronic state of Pt (XAS) and Pt surface structure (CO-stripping) were indistinguishable for all materials, we conclude that sorption effects of glucose play a crucial role in catalytic activity. This was further confirmed by establishing a relation between the annulus of the Pt particles and the activity.</p

Supported Pt-Re catalysts for the selective hydrogenation of methyl and ethyl esters to alcohols

The effect of Re-addition to Pt/TiO2catalysts for the hydrogenation of carboxylic acids and esters to their corresponding alcohols was investigated. The highest catalytic activity was observed for the materials with Pt:Re molar ratio of 1:2, which allowed for a complete conversion of hexanoic acid under mild conditions. The hydrogenation of esters over the same catalysts was much more difficult. The reactions showed only moderate alcohol yields which also depended strongly on the alkoxy moiety of the ester substrate. The highest yield of ca. 25% was achieved by the hydrogenation of ethyl hexanoate. Conversion of methyl hexanoate was much less efficient. This was attributed to the inhibiting effect of methanol by-product. In situ FTIR spectroscopy suggests that the decarbonylation of methanol and the resulting CO poisoning of the catalyst surface in the course of the reaction is the most likely cause of the low activity of Pt and Pt-Re/TiO2towards methyl ester hydrogenation

Relevance of chemical vs electrochemical oxidation of tunable carbene iridium complexes for catalytic water oxidation

Based on previous work that identified iridium(III) Cp* complexes containing a C,N-bidentate chelating triazolylidene-pyridyl ligand (Cp* = pentamethylcyclopentadienyl, C 5Me 5 –) as efficient molecular water oxidation catalysts, a series of new complexes based on this motif has been designed and synthesized in order to improve catalytic activity. Modifications include specifically the introduction of electron-donating substituents into the pyridyl unit of the chelating ligand (H, a; 5-OMe, b; 4-OMe, c; 4-tBu, d; 4-NMe 2, e), as well as electronically active substituents on the triazolylidene C4 position (H, 8; COOEt, 9; OEt, 10; OH, 11; COOH, 12). Chemical oxidation using cerium ammonium nitrate (CAN) indicates a clear structure-activity relationship with electron-donating groups enhancing catalytic turnover frequency, especially when the donor substituent is positioned on the triazolylidene ligand fragment (TOF max = 2500 h – 1 for complex 10 with a MeO group on pyr and a OEt-substituted triazolylidene, compared to 700 h – 1 for the parent benchmark complex without substituents). Electrochemical water oxidation does not follow the same trend, and reveals that complex 8b without a substituent on the triazolylidene fragment outperforms complex 10 by a factor of 5, while in CAN-mediated chemical water oxidation, complex 10 is twice more active than 8b. This discrepancy in catalytic activity is remarkable and indicates that caution is needed when benchmarking iridium water oxidation catalysts with chemical oxidants, especially when considering that application in a potential device will most likely involve electrocatalytic water oxidation

CCDC 1909357: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909358: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909354: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909363: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909361: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909355: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009

CCDC 1909359: Experimental Crystal Structure Determination

Related Article: Marta Olivares, Cornelis J. M. van der Ham, Velabo Mdluli, Markus Schmidtendorf, Helge Müller-Bunz, Tiny W.G.M Verhoeven, Mo Li, Hans J. W. Niemantsverdriet, Dennis G. H. Hetterscheid, Stefan Bernhard, Martin Albrecht, J. W. Hans Niemantsverdriet|2020|Eur.J.Inorg.Chem.|2020|801|doi:10.1002/ejic.20200009