Lithium Ion Battery Materials as Tunable, Redox Non-Innocent Catalyst Supports

The development of general strategies for the electronic tuning of a catalyst’s active site is an ongoing challenge in heterogeneous catalysis. To this end, herein we describe the application of Li-ion battery cathode and anode materials as redox non-innocent catalyst supports that can be continuously modulated as a function of lithium intercalation. A zero-valent nickel complex was oxidatively grafted onto the surface of lithium manganese oxide (LixMn2O4) to yield isolated Ni(II) occupying the vacant interstitial octahedral site in the Li diffusion channel on the surface and subsurface of the spinel structure (Ni/LixMn2O4). The activity of Ni/LixMn2O4 for olefin hydrogenation, as a representative probe reaction, was found to increase monotonically as a function of support reductive lithiation. Simulation of Ni/LixMn2O4 reveals the dramatic impact of surface redox states on the viability of the homolytic oxidative addition mechanism for H2 activation. Catalyst control through support lithiation was extended to an organotantalum complex on LixTiO2, demonstrating the generality of this phenomenon.

Development of Nickel- and Magnetite-Promoted Carbonized Cellulose Bead-Supported Bimetallic Pd–Pt Catalysts for Hydrogenation of Chlorate Ions in Aqueous Solution

Cellulose grains were carbonized and applied as catalyst supports for nickel- and magnetite-promoted bimetallic palladium- and platinum-containing catalysts. The bimetallic spherical aggregates of Pd and Pt particles were created to enhance the synergistic effect among the precious metals during catalytic processes. As a first step, the cellulose bead-based supports were impregnated by nitrate salts of nickel and iron and carbonized at 973 K. After this step, the nickel was in an elemental state, while the iron was in a magnetite form in the corresponding supports. Then, Pd and Pt particles were deposited onto the supports and the catalyst surface; precious metal nanoparticles (10–20 nm) were clustered inside spherical aggregated particles 500–600 nm in size. The final bimetallic catalysts (i.e., Pd–Pt/CCB, Pd–Pt/Ni–CCB, and Pd–Pt/Fe3O4–CCB) were tested in hydrogenation of chlorate ions in the aqueous phase. For the nickel-promoted Pd–Pt catalyst, a >99% chlorate conversion was reached after 45 min at 80 °C. In contrast, the magnetite-promoted sample reached an 84.6% chlorate conversion after 3 h. Reuse tests were also carried out with the catalysts, and in the case of Pd–Pt/Ni–CCB after five cycles, the catalytic activity only decreased by ~7% which proves the stability of the system.

FUNCTIONALIZATION OF THE SURFACE OF HYPERCROSSLINKED POLYSTYRENE FOR CATALYST SYNTHESIS

Нанесенные наноразмерные катализаторы широко используются в различных процессах химической технологии. При этом особые требования предъявляются к носителю, используемому при синтезе катализаторов. Сверхсшитые полимеры являются перспективными носителями, однако зачастую не имеют требуемых свойств (например, кислотности). Для придания дополнительных свойств возможно модифицировать поверхность полимеров различными веществами или функциональными группами. В данной работе проведено исследование способов модификации и веществ-предшественников кремнийсодержащей фазы для модификации поверхности сверхсшитого полистирола диоксидом кремния. The supported nano-scale catalysts are widely used in different fields of chemical engineering. For the catalysts, the certain requirements are specified fort the catalyst supports. Hypercrosslinked polymers seem to be the prospective materials for the catalyst synthesis. However, polymeric matrices often do not meet some standards for catalyst supports (i.e. polymers are inert materials and do not have the acidic or basic properties). To infuse the additional properties to polymers it is possible to modify its surface with different compounds or functional groups. In this work, the study of the ways for the modification of the surface of hypercrosslinked polystyrene and silica-phase precursors was carried out.

Atomic level fluxional behavior and activity of CeO2-supported Pt catalysts for CO oxidation

Reducible oxides are widely used catalyst supports that can increase oxidation reaction rates by transferring lattice oxygen at the metal-support interface. There are many outstanding questions regarding the atomic-scale dynamic meta-stability (i.e., fluxional behavior) of the interface during catalysis. Here, we employ aberration-corrected operando electron microscopy to visualize the structural dynamics occurring at and near Pt/CeO2 interfaces during CO oxidation. We show that the catalytic turnover frequency correlates with fluxional behavior that (a) destabilizes the supported Pt particle, (b) marks an enhanced rate of oxygen vacancy creation and annihilation, and (c) leads to increased strain and reduction in the CeO2 support surface. Overall, the results implicate the interfacial Pt-O-Ce bonds anchoring the Pt to the support as being involved also in the catalytically-driven oxygen transfer process, and they suggest that oxygen reduction takes place on the highly reduced CeO2 surface before migrating to the interfacial perimeter for reaction with CO.