Photoelectrochemical behaviour of ruthenium disulphide electrodes in contact with aqueous electrolytes

RuS₂, which is a semiconductor, has been prepared as a sintered material. As an electrode, it has a high catalytic activity for oxygen evolution from aqueous solution in the dark. On illumination, an oxidation reaction occurs at potentials more negatively by 1 V. This photoreaction with water was studied as a function of the photon energy, the pH of the electrolyte, and the electrochemical history of the electrode. The interpretation of the behaviour is complicated by the apparent dependence of the double layer potential on the total electrode potential and the pH which leads to a considerable shift of the bands of the semiconductor with respect to the redox levels of the electrolyte. Kinetic evidence also indicates the involvement of surface states in a reduction of the oxidation products of water. The remarkable photoelectrochemical stability of RuS₂ is discussed in terms of a high concentration of Ru d-states in the valence band and the presence of S₂^2? ions in the crystal lattice. The prospects for RuS₂ as a photocatalytic material for oxygen evolution seem promising, but a full evaluation is at present hampered by the occurrence of unfavourable side reactions, probably caused by the polycrystalline and porous nature of the available material. In this first investigation we study the microcrystalline sintered product which would be more likely to be a practical electrode. Later we will present a more fundamental study using single crystals of RuS₂.     

Zweiter Aerosol-Kongreß, Münster i.W. vom 5.–7. Oktober 1955

Ohne Zusammenfassung     

Experimental study of a metal-matrix composite

A metal-matrix specimen was investigated using moiré interferometry with 2400 ℓ/mm (60,960 ℓ/in.). The specimen was a 6-ply [0/±45] _s boron-aluminum tensile coupon with a central slot. The unequal deformations in fibers and matrix were evident. Special attention was given to a plastic slip zone in the matrix. Normal and shear strains were calculated in the slip zone; the shear-strain concentration factor rose dramatically with the onset of plastic slip and continued to rise gradually with load to 95 percent of the failure load. The precipitous change from maximum tensile strain in one fiber to zero tensile strain in the neighboring fiber was accommodated by the very high shear strain in the matrix in the slip zone. Experimental considerations are discussed: shear strains are independent of rigid-body rotations; simplified strain calculations are justified; averaging across the narrow slip region and the influence of finite thickness of the specimen grating contribute to underestimation of peak strains. Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.     

Tuning and predicting biological affinity: aryl nitriles as cysteine protease inhibitors

A series of aryl nitrile-based ligands were prepared to investigate the effect of their electrophilicity on the affinity against the cysteine proteases rhodesain and human cathepsin L. Density functional theory calculations provided relative reactivities of the nitriles, enabling prediction of their biological affinity and cytotoxicity and a clear structure-activity relationship.