Co catalysts supported on ceria supports with two different particle sizes, one in the micro-and the other in the nano-range, were investigated for their ethanol and ethylene steam reforming performance. Pre-and post-reaction characterization techniques, including high-resolution transmission electron microscopy, temperature-programmed oxidation, dispersion, pore size measurements, in situ X-ray diffraction (XRD) and X-ray absorption fine structure spectroscopy (XAFS) studies were performed to examine the reducibility of the catalysts. Steady-state-activity testing has shown nanoparticles to have a higher reforming activity for ethanol, but also high ethylene yields. In spite of the high ethylene yields, catalysts supported on nanoparticles proved to be highly resistant to coking while the catalysts supported on larger ceria particles suffered from coke formation. Reforming experiments performed with ethylene showed significant differences in activity and stability. Bare supports were also tested for activity and the nanoparticle support was seen to have high dehydration activity. Operando DRIFTS experiments performed during ESR showed differences in surface species. Pulse experiments performed to use methanol oxidation as a probe reaction suggested differences in the relative abundance of redox sites and basic sites. The bare ceria supports also exhibited significant activity for ethanol dehydration, but not for C−C cleavage. The superior performance of the catalysts supported on nanoparticles is thought to be due to a combination of factors, including increased reducibility, improved metal dispersion, and a difference in relative abundance of redox sites on the surface. All of these properties and, in turn, the catalytic performance, appear to be affected by the particle size of the support.

Coexistence of order and fluidity in soft matter often mimics that in biology, allowing for complex dynamics and applications-like displays. In active soft matter, emergent order can arise because of such dynamics. Powered by local energy conversion, this behavior resembles motions in living systems, like schooling of fish. Similar dynamics at cellular levels drive biological processes and generate macroscopic work. Inanimate particles capable of such emergent behavior could power nanomachines, but most active systems have biological origins. Here we show that thousands-to-millions of topological solitons, dubbed “skyrmions”, while each converting macroscopically-supplied electric energy, exhibit collective motions along spontaneously-chosen directions uncorrelated with the direction of electric field. Within these “schools” of skyrmions, we uncover polar ordering, reconfigurable multi-skyrmion clustering and large-scale cohesion mediated by out-of-equilibrium elastic interactions. Remarkably, this behavior arises under conditions similar to those in liquid crystal displays and may enable dynamic materials with strong emergent electro-optic responses.

Reducibility of ceria under steam reforming conditions and the effect of particle size on its reducibility was examined using two ceria samples with distinctly different mean particle sizes (3.5 nm versus 120 nm), but with similar polyhedral morphologies. The degree of reduction from Ce 4+ to Ce 3+ was characterized by temperature programmed reduction (TPR) and in situ X-ray absorption near edge structure spectroscopy (XANES) where the nanopolyhedra were observed to reduce much more readily compared to the larger particle-size sample. There was also significant reduction of the nanopolyhedra under ethanol steam reforming conditions. Ceria nanopolyhedra exhibited significantly more Ce 3+ sites which contributed to a lower occurrence of surface acidic sites. The acidic/basic sites were probed by probe molecules such as pyridine and CO 2 through in situ diffuse reflectance infrared spectroscopy (DRIFTS). The particle size also showed major differences in the steam reforming activity of ceria, with nanopolyhedra with a 3.5-nm mean particle size exhibiting significantly higher carbon cleavage and ethanol dehydration activity than its counterpart of 120 nm mean particle size.

Active colloids and liquid crystals are capable of locally converting the macroscopically supplied energy into directional motion and promise a host of new applications, ranging from drug delivery to cargo transport at the mesoscale. Here we uncover how topological solitons in liquid crystals can locally transform electric energy to translational motion and allow for the transport of cargo along directions dependent on frequency of the applied electric field. By combining polarized optical video microscopy and numerical modeling that reproduces both the equilibrium structures of solitons and their temporal evolution in applied fields, we uncover the physical underpinnings behind this reconfigurable motion and study how it depends on the structure and topology of solitons. We show that, unexpectedly, the directional motion of solitons with and without the cargo arises mainly from the asymmetry in rotational dynamics of molecular ordering in liquid crystal rather than from the asymmetry of fluid flows, as in conventional active soft matter systems.

The development of on-purpose 1,3-butadiene (BDE) technologies remains an active area in catalysis research, because of the importance of BDE in industrial polymer production. Here, we report on a nonoxidative dehydrogenation catalyst for the production of BDE prepared by atomically precise installation of platinum sites on a Zn-modified SiO 2 support via atomic layer deposition (ALD). In situ reduction X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), CO chemisorption, and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging of activated PtZn/SiO 2 , revealed the formation of a uniform, well-distributed subnanometer-to nanometer-sized PtZn (1.2 ± 0.3 nm) alloy as the active catalytic species.

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Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-vis, and solid-state (SS) NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H and TEM techniques revealed highly dispersed (methylcyclopentadienyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO, 1). In addition, computational modeling suggests that the surface reaction of (MeCp)PtMe with Zn(II)-modified SiO support is thermodynamically favorable (Δ G = -12.4 kcal/mol), likely due to the increased acidity of the hydroxyl group, as indicated by NH-TPD and DNP-enhanced O{H} SSNMR. In situ DRIFTS and XAS hydrogenation experiments reveal the probable formation of a surface Pt(IV)-H upon hydrogenolysis of Pt-Me groups. The heterogenized organoplatinum(IV)-hydride sites catalyze the selective partial hydrogenation of 1,3-butadiene to butenes (up to 95%) and the reduction of nitrobenzene derivatives to anilines (up to 99%) with excellent tolerance of reduction-sensitive functional groups (olefin, carbonyl, nitrile, halogens) under mild reaction conditions.

A synergistic effect has been uncovered between ppm levels of Pd and Ni embedded within iron nanoparticles that leads to selective catalytic reductions of nitro-containing aromatics in water.