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

Abstract

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 (Li x Mn 2 O 4 ) to yield isolated Ni 2+ occupying the vacant interstitial octahedral site in the Li diffusion channel on the surface and subsurface of the spinel structure (Ni/Li x Mn 2 O 4 ). The activity of Ni/Li x Mn 2 O 4 for olefin hydrogenation, as a representative probe reaction, was found to increase monotonically as a function of support reductive lithiation. Simulation of Ni/Li x Mn 2 O 4 reveals the dramatic impact of surface redox states on the viability of the homolytic oxidative addition mechanism for H 2 activation. Catalyst control through support lithiation was extended to an organotantalum complex on Li x TiO 2 , demonstrating the generality of this phenomenon.

Metal Site-Specific Electrostatic Field Effects on a Tricopper(I) Cluster Probed by Resonant Diffraction Anomalous Fine Structure (DAFS)

“…During our survey of different Cu-containing complexes using DAFS analysis, we discovered a case where individual Cu­(I) ions within a tricopper­(I) cluster are site-differentiated due to the presence of a nearby K + cation and its associated electrostatic field. The influence of cationic field effects on catalytic sites is an active area of investigation, − with ramifications on various energy storage and conversion schemes as well as fundamental understanding of both heterogeneous catalysts − and bioinorganic systems. − …”

Structural and reactive evolution of oxidatively grafted Pd catalysts on MnO2 for the low-temperature oxidation of CO

“…Recently, our group has demonstrated the well-defined interstitial doping of Ni on Li x Mn 2 O 4 by an electron transfer mechanism between the oxidizing surface and the low-valent precursor (Ni(COD) 2 , COD = cyclooctadiene). 20 We reason this strategy may afford well anchored isolated sites for comparable group 10 systems, particularly for resistance to agglomeration under reducing conditions. Herein, this oxidative grafting technique is applied to introduce Pd onto MnO 2 as a targeted oxidation catalyst.…”

Effects of surface acidity on the structure of organometallics supported on oxide surfaces

“…As the field of surface organometallic chemistry continues to grow more nuanced methods to evaluate how the support affects structure will likely be necessary. Acidity clearly plays a deciding role in the species described here, but there are supports, such as redox active battery materials, 174 where new metrics will be needed to accurately describe how thermodynamics properties of the surface affects structure of an organometallic or inorganic site active in a catalytic reaction.…”