Plenary Abstracts

Design Rules for Membranes from Polymers of Intrinsic Microporosity for Crossover-free Aqueous Electrochemical Devices
Miranda Baran, Berkeley Lab

The energy efficiency and cycle life of electrochemical cells with dissolved active materials are inextricably tied to the stability, conductivity, and transport selectivity of the cell?s membrane. Membrane design rules have been lacking for such cells operating under harsh conditions, such as high alkalinity, due to the lack of selective, stable membranes. We put forth design rules linking microporous polymer membrane architecture and pore chemistry to membrane stability, conductivity, and transport selectivity in aqueous electrolytes over a broad range of pH. Key to our success was the placement of ionizable amidoxime functionalities, which are stable at high pH, within the pores of microporous ladder polymer membranes, yielding a family polymer that we call AquaPIMs. By carefully selecting polymers with stable free volume elements and analyte specificity, we identified key structure?transport property relationships, which we tied to prospects for crossover-free electrochemical cell operation in three aqueous Zn-based cell chemistries. In doing so, we uncovered a simple relationship between the membrane selectivity and cell cycle life, such that it is now possible to predict the lifetime of the cell on the basis of its membrane properties, thus avoiding time- or resource-intensive experimentation in large-format cells.

Establishing Compositional Control in 2D and 3D Metal Sulfide Electrocatalysts to Drive CO2 and CO Conversion to Alcohols
Jesus Velazquez, UC Davis

The development of materials that address the growing dichotomy of simultaneously increasing energy demands and carbon emissions is an imperative that has progressively affected energy-related research efforts. An emerging technical avenue in this area is the conversion of vastly abundant renewable energy sources that can be harnessed and directed towards synthesis of traditionally fossil fuel-based products from atmospheric feedstocks like CO2. In order to translate such an energy conversion process into a viable technology, it is critical that design principles for novel Earth-abundant electrocatalyst materials be elucidated in order to mitigate operating costs while improving overall process efficiency.

This work establishes structure?function correlations for materials within the versatile classes of MX2 (M = Mo, W; X = S, Se) and Chevrel-Phase (CP) MyMo6X8 (M = alkali, alkaline, transition or post-transition metal; y = 0-4; X = S, Se, Te) chalcogenides. Specifically, the molybdenum sulfide structures from both families were found in our preliminary work to exhibit exceptional promise as CO2R catalysts. Hence the compositional and dimensional tunability of these crystal families may enable future development of structure?function correlations and design rules where composition, dimensionality, and electronic properties can be modulated to direct catalytic reactivity. Furthermore, we have identified the CP catalyst framework as being selective towards the electrochemical reduction of CO2 and CO to methanol (only major liquid-phase product) under applied potentials as mild as -0.4 V vs RHE. Moreover, intercalated CPs such as Cu2Mo6S8 exhibit interesting electronic signatures elucidated by X-ray absorption spectroscopy that indicates frontier orbital hybridization between Mo and S can be controlled via ternary intercalation. Indeed, we have correlated reactivity toward electrochemical reduction of CO2 and CO to methanol to potentially increased reactivity of chalcogen sites?identified via XAS by the filling of Mo 4d/ S3p hybridized electronic states by intercalant electron density. It is suspected that CO hydrogenation is the rate-limiting step in the CO2 and CO reduction to methanol on these surfaces, hence surmounting the energy barrier for this step will rely strongly on the ability of the underlying catalyst surface to facilitate hydrogenation. As a result, these reactive chalcogen sites, which neighbor Mo sites for CO binding, synergistically facilitate hydrogenation owing to their improved reactivity following ternary intercalation?motivating future searches for maximally promoting intercalant species.

Electronic Structure and Bonding at the Edge of the Periodic Table
Rebecca Abergel, UC Berkeley/Berkeley Lab

The transplutonium elements (atomic numbers 95-103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to those heavier actinides. Understanding the fundamental properties of these elements has long been restricted by their scarcity and radioactivity, even though it is essential to gain the ability to manipulate bonding at the atomic level. In addition to presenting a rich set of scientific and technical challenges, such understanding is critical to a number of applied problems including the development of new separation strategies for the nuclear fuel cycle, the need for decontamination after a nuclear accident or the use of radio-isotopes for new cancer treatments. Recent use of state-of-the-art luminescence sensitization and X-ray absorption spectroscopic techniques, combined with transmission electron microscopy studies, has enabled the investigation of heavy actinide coordination features, even with minute amounts of materials. The resulting data suggest a change between the electronic structure in Am and Cm compounds, which can be addressed using the Russell-Saunders coupling model (mostly arising from the electrons spin-spin and orbit-orbit couplings) and the later Bk, Cf, and Es, which see an increased spin-orbit coupling contribution, where j-j coupling becomes more important. This tantalizing prospect of a change in electronic structure regime, and hence in chemical bonding and properties, will be discussed.

Linking microstructure to transport at several lengthscales in conjugated polymers
Alberto Salleo, Stanford University

Carrier mobility in conjugated polymers continues to increase with recent reports of field-effect mobilities exceeding 10 cm2/V.s. Charge transport is intrinsically dependent on processes occurring across multiple lengthscales. In order to access order parameters at the molecular scale we use charge modulation spectroscopy combined with theory. This technique allows us to further differentiate field-induced and doping-induced charges and study how their delocalization depends on local structure and disorder. Furthermore, we study the mesoscale organization of polymers using new techniques in the transmission electron microscope. By combining 4D STEM and HRTEM we are able to study the microstructure across a range of length-scales in real space and reciprocal space. These techniques are used on homopolymers and donor-acceptor copolymers and allow to extract information about the microstructure that is typically not visible by inspection. Such multiscale studies of microstructure are instrumental in guiding our understanding of charge transport in conjugated polymers.

High-Resolution Nanoimprint Lithography for Optics and Metrology
Keiko Munechicka, HighRI Optics, Inc.

HighRI Optics develops functional printable polymers and nanofabrication processes to enable advanced applications in photonics and metrology. The first part of the talk will focus on developing novel high refractive index polymers for patterning optical elements to manipulate light in applications such as displays, fiber photonics, and AR/VR head mount displays. Our proprietary material has refractive index values up to 2.0, designed to be compatible with industrial nanoimprint processes.

The second half of the talk will focus on fabricating Binary Pseudo-Random (BPR) calibration samples for the beyond-resolution reconstruction of optical images. The patented BPR-based calibration and reconstruction method enables quantitative analysis of the imaging system (via Modulation Transfer Function, MTF). Using the model of MTF, users can recover the image data as if the tool were operating at the optimal conditions without using arbitrary image-enhancing methods. This would be the first technology to allow data reconstruction, metrologically, based on the measured MTF of metrology tools under various experimental setups.

Materials and Methods for Selective Ion Capture from Water
Ngoc Bui, University of Oklahoma

Freshwater use is one of the fundamental dimensions of the Planetary Boundaries framework. Addressing the inextricably linked water-energy-food security nexus is critical to promote societal stability and global sustainability. Despite intensive efforts, access to safe drinking water and nutrients is still at risk due mainly to exposure to toxic heavy metals found in various water streams and food webs. Heavy metals, released from geochemical cycles and anthropogenic activities, have posed major threats to environmental ecosystems and caused severe adverse effects to living species on Earth. Flexible platform technologies for efficient removal and/or recovery of trace amounts of these ions from water at low operational, energetic and environmental costs are thus essential. Adsorption- and membrane-based technologies promise to provide more efficient and economical separation solutions which are then applicable at large scale for sustainable water and energy. Meanwhile, an advanced understanding of molecular behaviors and transport mechanisms across material interfaces is crucial. In this presentation, I will describe our initial efforts in advancing adsorbents and membranes for precision separations of metal ions from the water environment, and in unraveling their corresponding structure-performance relationships.

In this talk, I will cover our recent findings on new design rules to control the mechanical property of conjugated polymers. I will first discuss our new methodology to measure thin-film mechanics and fractures in a strongly confined thin film state close to the real-world conditions. Through precisely controlled glass transition temperature for conjugated polymers, we can predict, control and manipulate the modulus of the conjugated polymers. This was also supported by molecular dynamics simulation. Neutron scattering for conjugated polymers provided unique information on the chain conformation and chain rigidity, thus can be correlated with molecular entanglement, consequently failure mechanism. Application of the new materials as active materials in organic field-effect transistors (OFETs) will also be discussed.