R-3 Repository :: Browsing by Author "Schipper, Desmond E."

Browsing by Author "Schipper, Desmond E."

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A TiO2/FeMnP Core/Shell Nanorod Array Photoanode for Efficient Photoelectrochemical Oxygen Evolution
(American Chemical Society, 2017) Schipper, Desmond E.; Zhao, Zhenhuan; Leitner, Andrew P.; Xie, Lixin; Qin, Fan; Alam, Md Kamrul; Chen, Shuo; Wang, Dezhi; Ren, Zhifeng; Wang, Zhiming; Bao, Jiming; Whitmire, Kenton H.
A variety of catalysts have recently been developed for electrocatalytic oxygen evolution, but very few of them can be readily integrated with semiconducting light absorbers for photoelectrochemical or photocatalytic water splitting. Here, we demonstrate an efficient core/shell photoanode with a highly active oxygen evolution electrocatalyst shell (FeMnP) and semiconductor core (rutile TiO2) for photoelectrochemical oxygen evolution reaction. Metal–organic chemical vapor deposition from a single-source precursor was used to ensure good contact between the FeMnP and the TiO2. The TiO2/FeMnP core/shell photoanode reaches the theoretical photocurrent density for rutile TiO2 of 1.8 mA cm–2 at 1.23 V vs reversible hydrogen electrode under simulated 100 mW cm–2 (1 sun) irradiation. The dramatic enhancement is a result of the synergistic effects of the high oxygen evolution reaction activity of FeMnP (delivering an overpotential of 300 mV with a Tafel slope of 65 mV dec–1 in 1 M KOH) and the conductive interlayer between the surface active sites and semiconductor core which boosts the interfacial charge transfer and photocarrier collection. The facile fabrication of the TiO2/FeMnP core/shell nanorod array photoanode offers a compelling strategy for preparing highly efficient photoelectrochemical solar energy conversion devices.
Anionic Bismuth Oxido Clusters with Pendant Silver Cations: Synthesis and Structures of {[Bi4(µ3-O)2(TFA)9Ag(tol)2]2} and {Bi4(µ3-O)2(TFA)10(AgPPh3)2}n
(Wiley, 2017) Andleeb, Sohaila; Donaldson, Samantha L.; Schipper, Desmond E.; Fernandez, Ismael I. Loera; ud Dean, Imtiaz; Whitmire, Kenton H.
Anionic Bismuth-Oxido Carboxylate Clusters with Transition Metal Countercations
(American Chemical Society, 2016) Fernandez, Ismael I. Loera; Donaldson, Samantha L.; Schipper, Desmond E.; Andleeb, Sohaila; Whitmire, Kenton H.
Six new anionic bismuth-oxido clusters containing trifluoroacetate ligands were prepared. These include two new Bi6O8 clusters: [M(NCMe)2(H2O)4]3[Bi6(μ3-O)4(μ3-OH)4(CF3CO2)12] with an octahedral Bi6O4(OH)4 core (M = Ni, 1a; Co, 1b) and four Bi4O2 clusters, {[Co(NCMe)6][Bi4(μ3-O)2(CF3CO2)10]}n (2a), {[Co{HC(MeCO)2(MeCNH)}2][Bi4(μ3-O)2(CF3CO2)10]·2[CF3CO2]·2[CF3CO2H]·2[H2O]}n (2b), {[Cu(NCMe)4]2[Bi4(μ3-O)2(CF3CO2)10]·2[CF3CO2H]}n (2c), and {[Me4N]2[Bi4(μ3-O)2(CF3CO2)10]·2[CF3CO2H]}n (2d). These are among the first bismuth-oxido anionic clusters synthesized, and the first to have transition metal countercations. The Bi6O8 anion in 1a and 1b is a high-symmetry octahedron. Additionally, two of the new Bi4O2 clusters are arranged in 1D polymeric structures via bridging carboxylate ligands. The cation in compound 2c had not been previously characterized and was also observed in the synthesis of [Co{HC(MeCO)2(MeCNH)}2][Bi(NO3)6] (3). The new compounds were characterized using single crystal X-ray crystallography and elemental analysis.
Bifunctional metal phosphide FeMnP films from single source metal organic chemical vapor deposition for efficient overall water splitting
(Elsevier, 2017) Zhao, Zhenhuan; Schipper, Desmond E.; Leitner, Andrew P.; Thirumalai, Hari; Chen, Jing-Han; Xie, Lixin; Qin, Fan; Alam, Md Kamrul; Grabow, Lars C.; Chen, Shuo; Wang, Dezhi; Ren, Zhifeng; Wang, Zhiming; Whitmire, Kenton H.; Bao, Jiming
Developing stable and efficient bifunctional catalysts for overall water splitting into hydrogen and oxygen is a critical step in the realization of several clean-energy technologies. Here we report a robust and highly active electrocatalyst that is constructed by deposition of the ternary metal phosphide FeMnP onto graphene-protected nickel foam by metal-organic chemical vapor deposition from a single source precursor. FeMnP exhibits high electrocatalytic activity toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Utilizing FeMnP/GNF as both the anode and the cathode for overall water splitting, a current density of 10 mA cm−2 is achieved at a cell voltage of as low as 1.55 V with excellent stability. Complementary density functional theory (DFT) calculations suggest that facets exposing both Fe and Mn sites are necessary to achieve high HER activity. The present work provides a facile strategy for fabricating highly efficient electrocatalysts from earth-abundant materials for overall water splitting.
Effects of Catalyst Phase on the Hydrogen Evolution Reaction of Water Splitting: Preparation of Phase-Pure Films of FeP, Fe2P, and Fe3P and Their Relative Catalytic Activities
(American Chemical Society, 2018) Schipper, Desmond E.; Zhao, Zhenhuan; Thirumalai, Hari; Leitner, Andrew P.; Donaldson, Samantha L.; Kumar, Arvind; Qin, Fan; Wang, Zhiming; Grabow, Lars C.; Bao, Jiming; Whitmire, Kenton H.
The comparative catalytic activities of iron phosphides, FexP (xﾠ= 1ﾖ3), have been established with phase-pure material grown by chemical vapor deposition (CVD) from single-source organometallic precursors. This is the first report of the preparation of phase-pure thin films of FeP and Fe2P, and their identity was established with scanning-electron microscopy, X-ray photoelectron spectroscopy, and powder X-ray diffraction. All materials were deposited on fluorine-doped tin oxide (FTO) for evaluation of their activities toward the hydrogen evolution reaction (HER) of water splitting in 0.5 M H2SO4. HER activity follows the trend Fe3P > Fe2P > FeP, with Fe3P having the lowest overpotential of 49 mV at a current density of 10 mA cmﾖ2. Density functional theory (DFT) calculations are congruent with the observed activity trend with hydrogen binding favoring the iron-rich terminating surfaces of Fe3P and Fe2P over the iron-poor terminating surfaces of FeP. The results present a clear trend of activity with iron-rich phosphide phases outperforming phosphorus rich phases for hydrogen evolution. The films of Fe2P were grown using Fe(CO)4PH3ﾠ(1), while the films of FeP were prepared using either Fe(CO)4PtBuH2ﾠ(2) or the new molecule {Fe(CO)4P(H)tBu}2ﾠ(3) on quartz and FTO. Compoundﾠ3ﾠwas prepared from the reaction of PCl2tBu with a mixture of Na[HFe(CO)4] and Na2[Fe(CO)4] and characterized by single-crystal X-ray diffraction, ESI-MS, elemental analysis, andﾠ31P/1H NMR spectroscopies. Films of Fe3P were prepared as previously described from H2Fe3(CO)9PtBu (4).
Gold coated iron phosphide core–shell structures
(Royal Society of Chemistry, 2017) Kelly, Anna T.; Filgueira, Carly S.; Schipper, Desmond E.; Halas, Naomi J.; Whitmire, Kenton H.
Core–shell particles Fe2P@Au have been prepared beginning with Fe2P nanorods, nanocrosses and nanobundles prepared from the solvothermal decomposition of H2Fe3(CO)9(μ3-PtBu). Iron phosphide structures can be produced from a single-source organometallic precursor with morphological control by varying the surfactant conditions to yield fiber bundles and dumbbell-shaped bundles ranging from nanometers to microns. Derivatization of the surfaces with γ-aminobutyric acid was used to attach Au nanoparticle seeds to the surface of the Fe2P nanoparticles followed by completion of the Au shell by reduction with formaldehyde or aqueous HAuCl4/CO, with the latter giving somewhat better results. Shell thickness ranged from an incomplete, partially coated Au shell to a thickness of 65 ± 21 nm by varying the amount of gold decorated precursor particles. Increasing the thicknesses of the Au shells produced a redshift in the plasmonic resonance of the resulting structures as was observed previously for FeOx@Au.
In pursuit of advanced materials from single-source precursors based on metal carbonyls
(Royal Society of Chemistry, 2019) Whitmire, Kenton H.; Schipper, Desmond E.
In this perspective, the development of single-source precursors and their relative advantages over multiple source approaches for the synthesis of metal pnictide solid state materials is explored. Particular efforts in the selective production of iron phosphide materials for catalytic applications are discussed, especially directed towards the hydrogen evolution and oxygen evolution reactions of water splitting.
Iron carbonyl clusters with ECl2 units (E = P, As)
(Elsevier, 2017) Schipper, Desmond E.; Chen, Jing-Han; Whitmire, Kenton H.
Reaction of [PPN][HFe(CO)4] (PPN = bis(triphenylphosphine)iminium) with PCl3 in a 1:1 ratio produced small amounts of [PPN][P{Fe(CO)4}2Cl2] ([PPN][Ia]). Reaction of [Et4N][HFe(CO)4] with AsCl3 in a 1:0.75 ratio in THF at −78 °C produced [Et4N][As{Fe(CO)4}2Cl2] ([PPN][Ib]) as the majority product. The compound [PPN][(CO)4FePCl2O] ([PPN][II]) was obtained from the reaction of Fe2(CO)9 with PCl3 in THF. In contrast, [Et4N][HFe(CO)4] reacted with PCl3 at −78 °C in a 2:1 ratio to yield [Et4N][Fe2(CO)6{(μ4-PFe(CO)4)2(μ-CO)}{μ-PCl2}] ([Et4N][III]) as the majority product. The compounds were characterized spectroscopically and by single-crystal X-ray diffraction analyses.
New Main-Group-Element-Rich nido-Octahedral Cluster System: Synthesis and Characterization of [Et4N][Fe2(CO)6(μ3-As){μ3-EFe(CO)4}2]
(American Chemical Society, 2016) Schipper, Desmond E.; Ikhlef, Djamila; Khalal, Samila; Saillard, Jean-Yves; Whitmire, Kenton H.
A series of clusters of the form [Et4N][Fe2(CO)6(μ3-As)}(μ3-EFe(CO)4)], where E is either P or As, were synthesized from [Et4N]2[HAs{Fe(CO)4}3] and ECl3. AsCl3 gives the As-only compound; PCl3 produces compounds having two As atoms with one P atom, or one As atom and two P atoms, and they can exist as two possible isomers, one of which is chiral. The As2P and AsP2clusters cocrystallize, and their structure as determined by single-crystal X-ray diffraction is given along with the structure of the As-only cluster. Analytical data as well as density functional theory calculations support the formation and geometries of the new molecules.
Nucleophilic porous carbon materials for CO2 and H2S capture
(2017-03-28) Tour, James M.; Hwang, Chih-chau; Schipper, Desmond E.; Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to methods of capturing a gas from an environment by associating the environment (e.g., a pressurized environment) with a porous carbon material that comprises a plurality of pores and a plurality of nucleophilic moieties. In some embodiments, the associating results in sorption of gas components (e.g., CO2 or H2S) to the porous carbon materials. In some embodiments, the methods of the present disclosure also include a step of releasing captured gas components from porous carbon materials. In some embodiments, the releasing occurs without any heating steps by decreasing environmental pressure. In some embodiments, the methods of the present disclosure also include a step of disposing released gas components and reusing porous carbon materials. Additional embodiments of the present disclosure pertain to porous carbon materials that are used for gas capture.
Porous carbon materials for CO2 separation in natural gas
(2017-10-03) Tour, James M.; Schipper, Desmond E.; Hwang, Chih-chau; Tour, Josiah; Jalilov, Almaz S.; Ruan, Gedeng; Li, Yilun; Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to materials for use in CO2 capture in high pressure environments. In some embodiments, the materials include a porous carbon material containing a plurality of pores for use in a high pressure environment. Additional embodiments pertain to methods of utilizing the materials of the present disclosure to capture CO2 from various environments. In some embodiments, the materials of the present disclosure selectively capture CO2 over hydrocarbon species in the environment.
Porous carbon materials for CO2 separation in natural gas
(2017-03-21) Tour, James M.; Schipper, Desmond E.; Hwang, Chih-chau; Tour, Josiah; Jalilov, Almaz S.; Ruan, Gedeng; Li, Yilun; Rice University; United States Patent and Trademark Office
In some embodiments, the present disclosure pertains to materials for use in CO2 capture in high pressure environments. In some embodiments, the materials include a porous carbon material containing a plurality of pores for use in a high pressure environment. Additional embodiments pertain to methods of utilizing the materials of the present disclosure to capture CO2 from various environments. In some embodiments, the materials of the present disclosure selectively capture CO2 over hydrocarbon species in the environment.
Synthesis of Hexagonal FeMnP Thin Films from a Single-Source Molecular Precursor
(Wiley, 2017) Leitner, Andrew P.; Schipper, Desmond E.; Chen, Jing Han; Colson, Adam C.; Rusakova, Irene; Rai, Binod Kumar; Morosan, Emilia; Whitmire, Kenton H.
The first heterobimetallic phosphide thin film containing iron, manganese, and phosphorus, derived from the single-source precursor FeMn(CO)8(μ-PH2), has been prepared using a home-built metal-organic chemical vapor deposition apparatus. The thin film contains the same ratio of iron, manganese, and phosphorus as the initial precursor. The film becomes oxidized when deposited on a quartz substrate, whereas the film deposited on an alumina substrate provides a more homogeneous product. Powder X-ray diffraction confirms the formation of a metastable, hexagonal FeMnP phase that was previously only observed at temperatures above 1200 °C. Selected area electron diffraction on single crystals isolated from the films was indexed to the hexagonal phase. The effective moment of the films (μeff=3.68 μB) matches the previously reported theoretical value for the metastable hexagonal phase, whereas the more stable orthorhombic phase is known to be antiferromagnetic. These results not only demonstrate the successful synthesis of a bimetallic, ternary thin film from a single-source precursor, but also the first low temperature approach to the hexagonal phase of FeMnP.
Thin Films of (Fe1–xCox)3P and Fe3(P1–xTex) from the Co-Decomposition of Organometallic Precursors by MOCVD
(American Chemical Society, 2016) Leitner, Andrew P.; Chen, Jing-Han; Schipper, Desmond E.; Whitmire, Kenton H.
A new method for preparing thin films of ternary transition metal phosphides has been developed. The ferromagnetic compound Fe3P has been doped with cobalt and tellurium by decomposing H2Fe3(CO)9PtBu with either Co3(CO)9PtBu or H2Fe3(CO)9Te via metal–organic chemical vapor deposition (MOCVD) onto a quartz substrate. Solid mixtures of the organometallic clusters were vaporized and decomposed at 400 °C to produce films that were subsequently annealed under vacuum at 650 °C for 24 h to afford crystalline films of (Fe1–xCox)3P (0.09 < x < 0.22) and Fe3(P1–xTex) (0.04 < x < 0.42). The films exhibit phase purity as confirmed by powder X-ray diffraction and X-ray photoelectron spectroscopy, which also confirmed the homogeneity of the films. Changes in elemental ratios were tracked by unit cell constants and ICP-OES analysis. Field-dependent magnetization measurements showed magnetic hysteresis with similar magnetic saturation values for each doped material. Thermogravimetric analysis was used to compare the Curie temperatures (Tc) of pristine Fe3P (thin film) and the doped films; Co-doping was found to lower the Tc by up to 7 °C and Te-doping had no observable effect on the Tc.

Browsing by Author "Schipper, Desmond E."

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