The structure of anhydrous nickel chloride in the ionic liquid 1-ethyl-3-methyl imidazolium chloride and aluminum chloride has been investigated with extended X-ray absorption fine structure ͑EXAFS͒ in both Lewis acid and Lewis base solutions. The EXAFS data of NiCl 2 •6H 2 O crystals were also recorded and analyzed to demonstrate the difference file technique. The difference file technique is used to obtain the structural information for the very closely spaced coordination shells of chloride and oxygen in NiCl 2 •6H 2 O and they are found to agree very closely with the X-ray diffraction data. The difference file technique is then used to analyze the nickel chloride in the ionic liquid solutions. Even though anhydrous NiCl 2 is more soluble in the basic solution than in the acidic solution, the EXAFS data show a single coordination of four chlorides in a tetrahedron around the nickel atom in the basic solution. In a weak acid solution, there are six chlorides in a single octahedral coordination shell around the nickel. However, in a strong acid solution, in addition to the octahedral chloride-coordination shell, there is a second coordination shell of eight aluminum atoms in the form of a simple cube.

Nickel chloride was studied with cyclic voltammetry and X-ray absorption spectroscopy in acidic and basic aluminum chloride/1-ethyl-3-methyl imidazolium chloride (EMIC) ionic liquids. Acidic melts display metal stripping peaks which are not observed in the basic melt. EXAFS analysis shows that the nickel is tetrahedrally coordinated with chloride ions in the basic solution. In the acidic solution the nickel is coordinated by six chloride ions that are also associated with aluminum ions.

The oxygen reduction reaction (ORR) is a major factor that drives galvanic corrosion. To better understand how to tune materials to better inhibit catalytic ORR, we have identified an in silico procedure for predicting elemental dopants that would cause common, natively formed titanium oxides to better suppress this reaction. In this work, we created an amorphous TiO2 surface model that is in good agreement with experimental radial distribution function data and contains reaction sites capable of replicating experimental ORR overpotentials. Dopant performance trends predicted with our quantum chemistry model mirrored experimental results, and our top three predicted dopants (Mn, Al, and V, each present at doping concentrations of 1%) were experimentally verified to lower ORR currents under alkaline conditions by up to 77% vs the undoped material. These results show the robustness of calculated thermodynamic descriptors for identifying poor, TiO2-based ORR catalysts. This also opens the possibility of using quantum chemistry to guide the design of coating materials that would better resist the ORR and presumably galvanic corrosion.

We generated molecular simulations of Cl– interacting at different sites in aluminum oxide models and carried out FEFF8 calculations to obtain the local l-projected density of states (LDOS) spectra. These are compared to our earlier experimental X-ray absorption near-edge structure (XANES) data in order to study the interactions of chloride ions with the passive oxide film on aluminum as a function of electrochemical potential at the Cl K edge. This led to a number of new insights in the mechanism of the breakdown of the passive film in chloride solutions. Importantly, we show the chloride first attacks the hydroxyl components of the aluminum oxide, penetrates the oxide film, and finally attacks the metal surface.

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