Browsing by Author "Maza, William A."

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    Cooperative electrochemical water oxidation by Zr nodes and Ni–porphyrin linkers of a PCN-224 MOF thin film
    Usov, Pavel M.; Ahrenholtz, Spencer Rae; Maza, William A.; Stratakes, Bethany; Epley, Charity Cherie; Kessinger, Matthew C.; Zhu, Jie; Morris, Amanda J. (Royal Society of Chemistry, 2016-10-06)
    Here, we demonstrate a new strategy for cooperative catalysis and proton abstraction via the incorporation of independent species competent in the desired reactivity into a metal–organic framework (MOF) thin film. The highly porous MOF, designated as PCN-224-Ni, is constructed by Zr–oxo nodes and nickel(II) porphyrin linkers. Films of PCN-224-Ni were grown in situ on FTO and were found to electrochemically facilitate the water oxidation reaction at near neutral pH.
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    Nanoparticulate Ni(OH)₂ Films Synthesized from Macrocyclic Nickel(II) Cyclam for Hydrogen Production in Microbial Electrolysis Cells
    Qin, Mohan; Maza, William A.; Stratakes, Bethany M.; Ahrenholtz, Spencer R.; Morris, Amanda J.; He, Zhen (Electrochemical Society, 2016-01-01)
    Hydrogen production in microbial electrolysis cells (MECs) is a promising approach for energy harvesting from wastewater. The kinetic barriers toward proton reduction necessitate the use of catalysts to drive hydrogen formation at appreciable rates and low applied potentials. Towards this end, cost effective alternatives to platinum catalysts are of paramount interest. In this study, Ni(OH)2 films were synthesized by electrophoretic deposition from a Ni(II)cyclam precursor solution at varying concentrations (6 mM, 15 mM, and 23 mM). The films were characterized by scanning electron microscopy and X-ray photo-electron spectroscopy to confirm the deposition of Ni(OH)2. The Ni(OH)2-modified electrodes were then examined by both traditional electrochemical measurements and in an MEC for hydrogen production. Tafel analysis indicates an exchange current density of ∼0.36 mA cm−2 with a Tafel slope of ∼120 mV decade−1 consistent with a rate determining proton adsoprtion step. The hydrogen production rates increased with increasing Ni(II)cyclam concentration in the precursor solution, with the 23 mM-derived film exhibiting a rate comparable to that of a Pt-based catalyst in MEC tests.
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    Ruthenium(ii)-polypyridyl zirconium(iv) metal-organic frameworks as a new class of sensitized solar cells
    Maza, William A.; Haring, Andrew J.; Ahrenholtz, Spencer Rae; Epley, Charity Cherie; Lin, Shaoyang; Morris, Amanda J. (The Royal Society of Chemistry, 2015-10-16)
    A series of Ru(II)L2L′ (L = 2,2′-bipyridyl, L′ = 2,2′-bipyridine-5,5′-dicarboxylic acid), RuDCBPY, -containing zirconium(IV) coordination polymer thin films have been prepared as sensitizing materials for solar cell applications. These metal–organic framework (MOF) sensitized solar cells, MOFSCs, each are shown to generate photocurrent in response to simulated 1 sun illumination. Emission lifetime measurements indicate the excited state quenching of RuDCBPY at the MOF–TiO2 interface is extremely efficient (>90%), presumably due to electron injection into TiO2. A mechanism is proposed in which RuDCBPY-centers photo-excited within the MOF-bulk undergo isotropic energy migration up to 25 nm from the point of origin. This work represents the first example in which a MOFSC is directly compared to the constituent dye adsorbed on TiO2 (DSC). Importantly, the MOFSCs outperformed their RuDCBPY–TiO2 DSC counterpart under the conditions used here and, thus, are solidified as promising solar cell platforms.