The effect(s) of SO 2 on the two types of active sites on Cu-SSZ-13 NH 3 −SCR catalysts, Z2Cu and ZCuOH, were investigated. Two Cu-SSZ-13 catalysts with Si:Al ratios of 6 and 30 were synthesized, and they provide very different distributions of these two active sites. Inductively coupled plasma optical emission spectroscopy (ICP-OES), H 2 temperature-programmed reduction (H 2 -TPR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were utilized to characterize catalyst samples and quantify the amounts of total Cu, Z2Cu and ZCuOH. In situ DRIFTS results show that Z2Cu and ZCuOH responses to low-temperature (<200 °C) SO 2 poisoning were site-dependent. Results of SO 2 and SO 2 + NH 3 temperatureprogrammed desorption (TPD) and DRIFTS experiments, supplemented with DFT calculations, revealed that the different observed responses correspond to different sulfur intermediates that form. On Z2Cu sites, SO 2 only adsorbs when it is cofed with NH 3 via formation of ammonium sulfate, with its fingerprint TPD feature at 380 °C. However, low-temperature interaction between SO 2 and ZCuOH leads to copper bisulfite species formation, which can be further oxidized to form copper bisulfate with increasing temperature. In terms of low-temperature SCR functionality, the activity of both Cu-SSZ-13 samples were found to be significantly inhibited by SO 2 . However, in terms of regeneration (i.e., desulfation) behavior, Cu-SSZ-13 with a Si:Al = 30 (higher ZCuOH compared to Z2Cu) seemed to require higher desulfation temperatures (>550 °C). Therefore, compared with Z2Cu, ZCuOH sites are more susceptible to severe low-temperature SO 2 poisoning because of the formation of more stable bisulfite and ultimately bisulfate species.

We study the electronic structure and valence states in LiNi x Mn y Co z O2 (NMC) materials and compare the resulting electronic, structural, mechanical, and thermal properties of a class of NMC compositions. The Jahn–Teller distortion in the transition metal (TM) octahedral complex allows us to determine the ionic states of the TM elements. The variation of Ni2+/Ni3+ and Co2+/Co3+ as the NMC composition changes alters the structural stability, electrical conductivity, lattice parameters, elastic modulus, and thermal stability. The theoretical predictions are in excellent agreement with the experimental results. Through intensive computational screening, we further show that long-range atomic ordering is absent in the NMC lattice due to the mixture of the ionic states and similar ionic radii of the TM elements. The first-principles modeling provides a theoretical foundation on a complete understanding of the physicochemical properties of NMC at the level of electronic structures.

Like silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS‐P) crystals can undergo mechanically induced structural transitions to exhibit superelasticity and ferroelasticity. These properties arise from cooperative and correlated molecular displacements and rotations in response to mechanical stress. By utilizing a bending‐induced ferroelastic transition of TIPS‐P, flexible single‐crystal electronic devices were obtained that can tolerate strains (ϵ) of more than 13 % while maintaining the charge carrier mobility of unstrained crystals (μ>0.7 μ0). Our work will pave the way for high‐performance ultraflexible single‐crystal organic electronics for sensors, memories, and robotic applications.

LiNi x Mn y Co z O 2 (NMC) is the current choice of cathode for high-performance Li-ion batteries. The structural and mechanical stability of NMC plays a vital role in determining the electrochemical performance of batteries. However, the dynamic mechanical properties of NMC during Li reactions are widely unknown because of the microscopic heterogeneity of composite electrodes as well as the challenge of mechanical measurement for air-sensitive battery materials. We employ instrumented nanoindentation in an inert environment to measure the elastic modulus, hardness, and interfacial fracture strength of NMC of a hierarchical meatball structure as a function of the state of charge and cycle number. The mechanical properties significantly depend on the lithiation state and degrade as the electrochemical cycles proceed. The results are further compared with the properties of bulk NMC pellets. We perform first-principles theoretical modeling to understand the evolution of the elastic property of NMC on the basis of the electronic structure. This work presents the first time systematic mechanical measurement of NMC electrodes which characterizes damage accumulation in battery materials over cycles.

Metal oxides hold the promise of high-capacity anodes for Li-ion batteries. Lithiation of binary metal oxides proceeds with two typical mechanisms: insertion and conversion. We characterize the two-step lithiation behavior of α-MoO 3 , namely, Li intercalation in the layered α-MoO 3 leads to the formation of crystalline Li 2 MoO 3 in the early stage of lithiation, and further Li insertion coverts Li x MoO 3 to metallic Mo and amorphous Li 2 O. The intercalation process is thermodynamically more favorable and is accompanied with a minor volumetric change, while the conversion reaction is kinetically slow and induces large deformation. Furthermore, instead of showing significant Li-embrittlement as seen in typical oxides, α-MoO 3 remains defects free despite the nearly 100% repetitive volumetric change during lithiation cycles. The reaction mechanism, structural evolution, and mechanical behaviors are unveiled through coordinated insitu transmission electron microcopy experiments on α-MoO 3 nanobelts and first-principles computational studies. The results provide fundamental perspectives in the course of developing reliable high-capacity electrodes for Li-ion batteries.