Surface characterization of polymer‐stabilized colloidal metal catalysts

A new method for measuring hydrogen chemisorption on polymer‐stabilized metal colloids, in conjunction with variable coverage infrared spectroscopy of adsorbed CO, is applied to analyse the surface of Pt/polyvinylpyrrolidone colloids. The results correlate well with the measured activity of Pt/PVP as a hydrogenation catalyst.     

P,Se-Heterocycles From the Quasi-Binary System PhP/Se

Abstract

Contrary to statements in the literature the PhP/Se system does contain a compound with a PhP/Se ratio lower than 1. The reaction of pentaphenyl-cyclopentaphosphane and elemental selenium yields depending on the molar ratio the heterocyclic compounds (PhP)₄Se (1), (PhP)₃Se₃ (2), or (PhP)₂Se₄ (3). 1, 2, and 3 are yellow to orange-red crystalline stable compounds. Their molecular structures, as shown by the ³¹P- and ⁷⁷Se-NMR data as well as by the X-ray crystal structure determination of 2, parallel those of the corresponding sulfur derivatives. Nucleophiles add easily to the phosphorus in 3 splitting the P₂Se₂-ring.     

Basicity and Electrolyte Composition Dependent Stability of Ni-Fe-S and Ni-Mo Electrodes during Water Splitting

Non-noble metal electro-catalysts for water splitting are highly desired when we are moving towards a society where green electrons are becoming abundantly available, offering clear prospects to make our society more sustainable. In this work, Ni−Fe−S is reported as a high performing anode material for the water splitting reaction, operating at low overpotentials and showing high apparent stability. Furthermore, Ni−Mo electrodes are developed on metallic foam substrates and optimized in terms of their performance. The Ni−Fe−S material as anode, combined and integrated with Ni−Mo as cathode in a cell configuration, splits water at 10 mA cm⁻² and a potential of 1.55 V. Similar to previous reports, we confirm that Mo leaches from Ni−Mo/Ni foam electrodes. Cycling tests and ICP-AES measurements show that the stability of Ni−Fe−S is apparent, and that in reality S is leaching from the material as was already suggested in literature. We expand on this knowledge and show that the leaching of S is dependent on both pH and the cation used during electrocatalysis. Furthermore, we find that applying an oxidative potential is in truth stabilizing towards S and that the alkalinity causes leaching. S was furthermore mobile and found to segregate towards the surface. Finally, using too low pH values (11 and lower) result in the passivating hydroxide metal layers being destroyed and the Ni−Fe−S dissolving completely.