H. S. Jarrett

Semiconducting oxide anodes in photoassisted electrolysis of water

The electrochemical properties of semiconducting anodes of TiO2, SrTiO3, BaTiO3, Fe2O3, CdO, CdFe2O4, WO3, PbFe12O19, Pb2Ti1.5W0.5O6.5, Hg2Ta2O7, and Hg2Nb2O7 in photoassisted electrolysis of water were determined. All of these oxides formed a rectifying junction with the electrolyte and anodic photocurrents were generated only with larger‐than‐band‐gap illumination. For Fe2O3, the optical absorption spectrum was different from the photoelectrochemical spectrum due to crystal field transitions. These oxides were found to be stable over certain range of pH. In a given electrolyte, the flatband potential Vfb varied linearly with the band gap. A good correlation was obtained between Vfb and the heat of formation of the oxide per metal atom per metal‐oxygen bond, but not between Vfb and the calculated Fermi energy of the oxide. This suggests that a semiconductor‐electrolyte interface may be approximated by a semiconductor‐metal junction where the barrier height is determined by the heat of formation of the me...

Paramagnetic Resonance in Trivalent Transition Metal Complexes

Paramagnetic‐resonance absorption has been observed in complexes of acetylacetone with the trivalent transition metals titanium, chromium, iron, molybdenum, and ruthenium. The symmetry of the field perturbing the metal ion is predominantly axial. For the complexes of Ti+3 and of Ru+3, the axial potential is negative. Energy‐level splittings by the ligand field and g factors were obtained for the various complexes. Resonance was also observed in complexes of trifluoroacetylacetone with chromium and iron and in the complex chromium (III) hexafluoroacetylacetonate. Resonance could not be detected in the complexes vanadium (III) acetylacetonate, manganese (III) acetylacetonate and ferric (III) hexafluoroacetylacetonate, although magnetic‐susceptibility measurements on the last two compounds indicated that they were paramagnetic.

Photoelectrochemical and solid-state properties of LuRhO3

Rare‐earth rhodates of the distorted perovskite structure are semiconductors with a band gap of 2.2 eV. They may be doped either n or p type. The oxides are stable against photodecomposition at the potential for hydrogen evolution. With ceramic p‐type LuRhO3 as the cathode and n‐type TiO2 as the anode of an electrolytic cell sufficient photopotential is developed both to photoelectrolyze water in sunlight with no externally applied potential and to generate power simultaneously. As synthesized, LuRhO3 is p type as determined by thermoelectric power measurements, but may be doped n type by the introduction of Th+4 during synthesis. Electrical resistivity data show that this oxide passes through compensation as the doping level increases, the activation energy at compensation being one‐half the optical band gap. The concentration of donor and acceptor impurities was determined by magnetic susceptibility to be in the vicinity of 1% for all samples. From these data, an estimate of 2.5 cm2/V sec can be made fo...

Paramagnetic Resonance Absorption in Some Organic Biradicals

Four compounds of the form 4,4′‐polymethylenebistriphenylmethyl, one compound of the form (1,4‐phenylene)bisdiarylmethyl, three compounds of the form (4,4′‐biphenylene)bisdiarylmethyl, and one compound, 4,4′‐oxybistriphenylmethyl have been shown to possess unpaired electrons by paramagnetic resonance absorption. The resonance spectra of 0.01 M solutions of these compounds in benzene exhibit a hyperfine structure arising from a spherically symmetrical contribution of the magnetic dipole interaction between the unpaired electron and the nuclear magnetic moments of the hydrogen atoms. The g‐factors for the compounds investigated in the first three classes were found to be 2.0025±0.0004 and 2.0031±0.0004 for the last compound. Such a close approach of the g‐factor to the free electron value plus the sharpness of the hyperfine structure lines indicates that the anisotropic contributions of the spin‐orbit interaction, which would normally lift the degeneracy of the triplet state, are averaged out by the tumblin...

Photoelectrochemical properties of LuRhO3

Abstract Rare earth rhodates of the distorted perovskite structure are semiconductors with a band gap of 2.2 eV. They may be doped either n- or p-type. The oxides are stable against photodecomposition at the potential for hydrogen evolution. With ceramic p-type LuRhO 3 as the cathode and n-type TiO 2 as the anode of an electrolytic cell sufficient photopotential is developed both to photoelectrolyze water in sunlight with no externally applied potential and to generate power simultaneously. LuRhO 3 possesses deep lying impurity levels and surface capacitance does not exhibit ideal Mott-Schottky behavior. The Fermi level at the surface of LuRhO 3 is pinned at the same potential independent of whether the oxide is p- or n-type.

Generalization of Crystal Field Theory to Include Covalent Bonding

A potential operator with many of the features of the crystal field potential of Bethe and Van Vleck but which explicitly accounts for any degree of covalent bonding between metal and ligand is derived starting from antisymmetrized molecular orbitals.

Effect of Electron Scattering on Ferromagnetic Band Width

The influence on the pseudoparticle density of states of the three scattering terms (spin disorder scattering and two resonance broadening terms) treated in Hubbard III for a half‐filled band is investigated in the ferromagnetic regime. For a given magnetization the minority band width increases with each scattering term included. For full Hubbard III, no band width renormalization is found. Hubbard III incorrectly gives the ferromagnetic state lower than the nonmagnetic for a half‐filled band.