Metal ions exchanged on zeolites represent a unique bridge between heterogeneous solid materials and homogeneous inorganic chemistry. The complexing of exchanged metal ions with H2O or NO, is of particular relevance for a number of reactions, including the ubiquitous presence of both gases in pollution remediation technologies. Here, we interrogate the molecular structure of Pd cations in SSZ-13 zeolites and their interaction with H2O and NO using experimental and computational analyses. Density functional theory (DFT) and spectroscopic characterization establish that Pd cations preferentially populate two Al (2Al) sites in the six-membered ring as PdII. In situ spectroscopic and kinetic analyses follow the Pd coordination environment and reactivity as a function of environmental conditions, and molecular structures are rationalized through ab initio molecular dynamics and first-principles thermodynamic modeling. Experiment and computational modeling together reveal that, at temperatures <573 K, Pd ions are solvated and mobilized by H2O molecules, promoting catalytic CO oxidation, and form molecular complexes akin to their Pd homogeneous analogues. Exposure to NO promotes transformation from 2Al → 1Al charge-compensated H2O-solvated Pd-nitrosyl complexes, which desorb NO at higher temperatures and inhibit CO adsorption and oxidation. A comparison with Pd-BEA and Pd-ZSM-5 zeolites demonstrates a heterogeneous distribution of Pd-NO complexes under dry conditions that coalesce into homogeneous H2O-solvated Pd-nitrosyl complexes upon exposure to H2O.

The technical and economic feasibility of applying used electric vehicle (EV) batteries in stationary applications was evaluated in this study. In addition to identifying possible barriers to EV battery reuse, steps needed to prepare the used EV batteries for a second application were also considered. Costs of acquiring, testing, and reconfiguring the used EV batteries were estimated. Eight potential stationary applications were identified and described in terms of power, energy, and duty cycle requirements. Costs for assembly and operation of battery energy storage systems to meet the requirements of these stationary applications were also estimated by extrapolating available data on existing systems. The calculated life cycle cost of a battery energy storage system designed for each application was then compared to the expected economic benefit to determine the economic feasibility. Four of the eight applications were found to be at least possible candidates for economically viable reuse of EV batteries. These were transmission support, light commercial load following, residential load following, and distributed node telecommunications backup power. There were no major technical barriers found, however further study is recommended to better characterize the performance and life of used EV batteries before design and testing of prototype battery systems.

3We report a mechanistic DRIFTS in-situ study of NO 2 , NO + O 2 and NO adsorption on a 4 commercial Cu-CHA catalyst for NH 3 -SCR of NOx. Both pre-reduced and pre-oxidized catalyst 5 samples were investigated with the aim to clarify mechanistic aspects of the NO oxidation to NO 2 6 as a preliminary step towards the study of the Standard SCR reaction mechanism at low 7 temperatures. Nitrosonium cations (NO + , N oxidation state = +3) were identified as key surface 8 intermediates in the process of NO (+2) oxidation to NO 2 (+4) and nitrates (+5). While NO + and 9 nitrates were formed simultaneously upon catalyst exposure to NO 2 , nitrates evolved consecutively 10 to NO + when the catalyst was exposed to NO + O 2 , suggesting that nitrite-like species, and not NO 2 , 11 are formed as the primary products of the NO oxidative activation over Cu-CHA. Upon catalyst 12 exposure to NO only, i.e. in the absence of gaseous O 2 , NO + and then nitrates were formed on a 13 preoxidized sample but not on a prereduced one, which demonstrates the red-ox nature of the NO 14 oxidation mechanism. The negative effect of H 2 O on NO + and nitrates formation was also clearly 15 established. Assuming small Cu clusters, in the form of Cu dimers, as the active sites for NO 16 oxidation to NO 2 , we propose a mechanism which reconciles all the experimental observations. In 17 particular, we show that such a mechanism also explains the observed kinetic effects of H 2 O, O 2 18 and NO 2 on the NO oxidation activity of the investigated Cu zeolite catalyst. 19 20 21

The development and optimization of catalysts and catalytic processes requires knowledge of reaction kinetics and mechanisms. In traditional catalyst kinetic characterization, the gas composition is known at the inlet, and the exit flow is measured to determine changes in concentration. As such, the progression of the chemistry within the catalyst is not known. Technological advances in electromagnetic and physical probes have made visualizing the evolution of the chemistry within catalyst samples a reality, as part of a methodology commonly known as spatial resolution. Herein, we discuss and evaluate the development of spatially resolved techniques, including the evolutions and achievements of this growing area of catalytic research. The impact of such techniques is discussed in terms of the invasiveness of physical probes on catalytic systems, as well as how experimentally obtained spatial profiles can be used in conjunction with kinetic modeling. Furthermore, some aims and aspirations for further evolution of spatially resolved techniques are considered.

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