Cubic Co3O4 nanoparticles with average diameters of 5.9, 21.1, and 46.9 nm (hereafter small, medium, and large) have been synthesized and characterized by pXRD, TEM, and BET. The nanoparticles were loaded onto Ni foam supports for evaluation as anodes for water electrolysis in 1.0 M KOH. Current densities of 10 mA/cm2 were achieved at overpotentials of 328, 363, and 382 mV for anodes loaded with 1 mg/cm2 of small, medium, and large sized Co3O4 nanoparticles, respectively. The activity correlates with the BET surface area of the isolated particles. A plot of the electrochemical overpotential at 10 mA/cm2 against the log of the BET surface area gives a linear relation with a slope of −47 ± 7 mV/dec, showing unequivocally that the activity increase is a function of accessible catalyst surface area.

Thermopower measurements offer an alternative transport measurement that can characterize the dominant transport orbital and is independent of the number of molecules in the junction. This method is now used to explore the effect of chemical structure on the electronic structure and charge transport. We interrogate junctions, using a modified scanning tunneling microscope break junction technique, where: (i) the 1,4-benzenedithiol (BDT) molecule has been modified by the addition of electron-withdrawing or -donating groups such as fluorine, chlorine, and methyl on the benzene ring; and (ii) the thiol end groups on BDT have been replaced by the cyanide end groups. Cyanide end groups were found to radically change transport relative to BDT such that transport is dominated by the lowest unoccupied molecular orbital in 1,4-benzenedicyanide, while substituents on BDT generated small and predictable changes in transmission.

Addition of 2,2‘-bipyridyl to diamagnetic (Me5C5)2Yb(OEt2) gives the brown adduct (Me5C5)2Yb(bipy). The solution 1H NMR and electronic absorption spectra show that the bipyridyl complex is paramagnetic, containing a bipyridyl radical anion, which can also be detected in the solid-state infrared spectrum and by the single-crystal X-ray crystallographic analysis. However, the measured magnetic moment, which varies from less than 1 μB at 5 K to 2.5 μB at 300 K, is higher than expected for (Me5C5)2YbII(bipy0) and less than expected for (Me5C5)2YbIII(bipy-). An electron exchange model for spin coupling between Yb(III), with electron configuration 4f13, and the single unpaired electron in the bipyridyl radical anion is presented, based on comparison with the iodide salt [(Me5C5)2YbIII(bipy0)]+[I]-. Comparing the magnetic susceptibility of (Me5C5)2Yb(phen) with its iodide salt shows similar behavior with phenanthroline as ligand. The extent of paramagnetism and therefore the exchange coupling is changed by the nature of the substituents on the cyclopentadienide rings; electron-withdrawing SiMe3 groups favor Yb(II), while electron-donating alkyl groups stabilize the Yb(III) species. The molecular structures of many of the compounds have been determined in the solid state, and the bond distances and angles are consistent with the interpretation of the magnetism. The ring substituents, and therefore the different magnetic environments about the ytterbium center, also influence the rate of intermolecular exchange of the heterocyclic base ligands in solution; when the ligand is reduced, it exchanges more slowly than in the diamagnetic compounds.

Transport in metal-molecule-metal junctions is defined by the alignment and coupling of molecular orbitals with continuum electronic states in the metal contacts. Length-dependent changes in molecular orbital alignment and coupling with contact states were probed via measurements and comparisons of thermopower (S) of a series of phenylenes and alkanes with varying binding groups. S increases linearly with length for phenylenediames and phenylenedithiols while it decreases linearly in alkanedithiols. Comparison of these data suggests that the molecular backbone determines the length dependence of S, while the binding group determines the zero length or contact S. Transport in phenylenes was dominated by the highest occupied molecular orbital (HOMO), which aligns closer to the Fermi energy of the contacts as approximately L(-1), but becomes more decoupled from them as approximately e(-L). In contrast, the decreasing trend in S for alkanedithiols suggests that transmission is largely affected by gold-sulfur metal induced gap states residing between the HOMO and lowest unoccupied molecular orbital.

Iron-doped nickel (oxy)hydroxide catalysts (Fe x Ni 1−x OOH) exhibit high electrocatalytic behavior for the oxygen evolution reaction in base. Recent findings suggest that the incorporation of Fe 3+ into a NiOOH lattice leads to nearly optimal adsorption energies for OER intermediates on active Fe sites. Utilizing electrochemical impedance spectroscopy and activation energy measurements, we find that pure NiOOH and FeOOH catalysts exhibit exceedingly high Faradaic resistances and activation energies 40−50 kJ/mol −1 higher than those of the most active Fe x Ni 1−x OOH catalysts. Furthermore, the most active Fe x Ni 1−x OOH catalysts in this study exhibit activation energies that approach those previously reported for IrO 2 OER catalysts.

A variety of transition-metal complexes with terminal silylene ligands have become available in recent years, because of the discovery of several preparative methods. In particular, three general synthetic routes to these complexes have emerged, on the basis of anionic group abstraction, coordination of a free silylene, and alpha-hydrogen migration. The direct transformation of organosilanes to silylene ligands at a metal center (silylene extrusion) has also been observed, and this has further spurred the exploration of silylenes as ligands. This Account describes the synthetic development of silylene ligands in our laboratory and resulting investigations of stoichiometric and catalytic chemistry for these species.

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Cobalt metaphosphate Co(PO3)2 nanoparticles are prepared via the thermolytic molecular precursor (TMP) method. A Ni form electrode decorated with Co(PO3)2 nanoparticles is evaluated as an anode for water oxidation electrocatalysis in pH 6.4 phosphate‐buffered water. Catalytic onset occurs at an overpotential of ca. 310 mV, which is 100 mV lower than that observed for Co3O4 nanoparticles, with a comparable surface area under identical conditions. A per‐metal turnover frequency (TOF) of 0.10–0.21 s−1 is observed at an overpotential, η, of 440 mV, which is comparable to the highest rate reported for a first‐row metal heterogeneous catalyst. Post‐catalytic characterization of the catalyst resting state by X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy reveals that surface rearrangement occurs, resulting in an oxide‐like surface overlayer.