Without a doubt, industry has created an amazing variety of molecules and materials that go into the products that are a large part of our modern way of life. For a majority of the chemicals and compounds outside of the pharmaceutical industry, we have a limited amount of information upon which to make reasonable decisions about their toxicity to humans or the environment, their degradability (biological or otherwise), our ability to recycle or reuse them, or their renewability.
Society is heavily dependent on the products of the chemical industry; however, most of us know very little about where the basic building blocks come from, at what social and environmental cost, and if there are any elements facing critical supply constraints. For many elements that are of critical importance, like those used in catalysis, electronics and energy production, we are taking a large amount of mass, concentrating the desired elements and dispersing these same elements into a form that is sometimes difficult to recover and reuse.
This talk will set the context for the problem, discuss several compelling examples where key material life cycles need to be closed, and discuss a way forward.

Energy, water use, and environmental impacts are among the first topics that researchers consider in sustainable materials development. However, minimizing the negative human health impacts of materials and their production processes is just as critical to ensuring the safety of current and future generations.
Spurred by recent industry actions, such as internal retailer policies (e.g. chemical "red lists") and green building rating systems like Leadership in Energy and Environmental Design (LEED) that are incorporating more stringent requirements around materials impacts, manufacturers are increasingly expected to account for both the environmental and human health aspects of their products. Because of this, they are looking for ways to redesign or reformulate their products to meet the needs of the changing marketplace. In some cases, manufacturers have difficulty finding substitutions for chemical and material ingredients deemed unsuitable due to their negative effects.
This situation presents both new considerations for researchers creating novel materials destined for the marketplace, as well as new opportunities for research into safer material chemistries and processing methods.
This talk will make a case for human health considerations being an integral, yet oft-overlooked, component of sustainable materials development. It will highlight important governmental policies and regulations in this arena, recent industry actions impacting environmental and human health considerations of materials, and present new opportunities for research.

There has been a recent move by scientists and engineers in the United States to tailor some of their work for developing countries and areas. The idea is that engineering can help to meet some of the basic needs of impoverished people, raise their standard of living, and create more sustainable communities. Past projects have included attempts to provide off-the-grid energy, clean water, and wastewater treatment and/or disposal. The interest in this topic can be seen in the variety of efforts to outline engineering strategies for the Millennium Development Goals and the fact that it is increasingly difficult to find a major university that does not have an active Engineers without Borders program.
Unfortunately the history of the modern world&’s attempts to address impoverished areas through technology transfer is riddled with failures. Sometimes the technologies sit unused weeks after they are introduced. Sometimes the technologies disrupt the social fabric of the community. Problems like these arise not because the motives of the engineers were necessarily bad, but because their training is mainly in technical areas and only a small part of the overall problem is technical in nature. There are rare occasions when technologies mesh with the infrastructure, social frameworks, and needs of the community to enable positive lasting change. These successes come only when the designers involved understand the people they are working with. And even then a fair amount of luck is needed.
This presentation will cover the basic lessons developed for a training program designed to help engineers and scientists interested in addressing the problems of t\he developing world. The two day workshop has already been held at Georgia Tech and the University of the Western Cape in South Africa and by the time of the fall MRS meeting it will have been held at Concordia in Montreal as well as Arizona State University. The workshop does not give participants everything they need to know to be able to engage in development work, but helps them to avoid some of the common pitfalls that doom many projects at the earliest stages.
Most significantly the workshop focuses on the importance of working to understand the relationship between technology, people, and the environment and provides tools to begin to learn more about their interactions. It argues that the key to any successful project is successful engagement. Outsiders will never be able to understand the context of the situation well enough to create a successful design. Opening up ways of communicating with the community are crucial even as early as the first step of defining what problem might be useful addressed. The workshop illustrates the dangers of not listening and provides techniques for engineers and scientists to better listen to the people they want to help and observe the environment in which they will work.

Proponents for sustainable alternative lighting and display options advocate for organic light-emitting diodes, particularly polymer light-emitting diodes (PLEDs) whose color range extends the entire visible spectrum, because of their potential low-cost fabrication, low operating voltage, and low power consumption. In this work, a materials life-cycle analysis was completed for three alternative device configurations to the conventional bottom-emitting PLED device structure - inverted bottom-emitting, conventional top-emitting and inverted top-emitting - due to their potential to increase device operational lifetime (inverted) and light out-coupling efficiency (top-emitting). The study was completed in terms of the following metrics: materials cost, projected total life cost savings, life-cycle power cost, and operating energy consumption per unit area. We find that glass, indium tin oxide (ITO), and conjugated polymer active-layer materials are the main contributors to materials cost for the conventional bottom-emitting device, accounting for 70 %, 12 %, and 14 % of the materials cost, respectively. This is a result of the large glass layer thickness (greater than1000 µm) compared to other device layers (less than 142 nm) and the high cost to fabricate both ITO and the active-layer materials. Approaches to increase the total life cost savings are: implementation of device designs that utilize thinner glass substrates that can be re-used following a device lift-off process; elimination of indium tin oxide; and increasing device operating lifetime and efficiency. We will show that the conventional bottom-emitting device has the lowest total life cost savings, approximately 3 times that of its top-emitting counterpart, while the inverted top-emitting device has the lowest life-cycle power cost and operating energy consumption per unit area due to its approximately 1.5 times longer operational lifetime and its factor of 2 reduction in power consumption. In addition, electromagnetic simulations of light extraction efficiency and the percentage of light energy trapped or absorbed in each layer of the devices will be presented and considered alongside the other metrics to select the optimal device architecture in terms of efficiency, cost and environmental factors.

The availability of drinking water and water reuse for agriculture or industrial purposes has been increasingly facilitated by membrane technology. Well-established processes like reverse osmosis dominates the market for water desalination. Other emerging processes are being implemented with the development of membranes with a diverse set of properties. Examples are nanofiltration for partial desalination of seawater for agriculture, forward osmosis for hybrid water reuse systems, microbial fuel cell and pressure-retarded osmosis for water-energy recovery. Our group has been dedicated to the synthesis of new polymers, their functionalization and morphology control aiming at the application to water-based separations. We focus on the development of porous membranes, which depending on hydrophobicity can be applied membrane distillation (MD) and ultrafiltration, as well as support for multilayer nanofiltration or forward osmosis membranes. We have been working for instance with fluorinated polyoxadiazoles and polytriazoles for MD. Analogous polymers with different chemical functionalizations have been used to manufacture solvent resistant membranes (hollow fiber and flat-sheet) for ultrafiltration and as support for forward osmosis. Besides chemical functionality, morphology control is a challenging task. Most of the available membranes have a broad range of pore size distribution. We have been exploring special techniques based on block copolymers to enable the manufacture of membranes with exceptional high and regular porosity. Recent advances and strategies for membrane manufacture for water-based separations will be summarized.

A paradigm shift towards renewable fuels like biodiesel comes with the adverse aspect of excess raw glycerol byproduct, fermentation of which to 1,3 propanediol provides a sustainable recourse to waste utilization. However, the downstream enrichment of such polar organics, typically produced in dilute mixtures, constitutes a major process efficiency bottleneck. Although membrane separation processes offer cheap and energy efficient alternatives of upgrading the concentration, high water affinity of 1,3 propanediol compounds the difficulty in pervaporative enrichment prompting the need to develop novel materials. The synthesis of a novel hydrophobic imidazolium ionic liquid salt monomer and its polymerization and copolymerization is presented. The monomer chemically anchors a hydrophobic high boiling solvent via a Menshutkin like pathway. The polymers are characterized by spectroscopy, thermal analysis, thin film water contact angle and mass uptake. A plug membrane is fabricated from these polymers and evaluated for batch pervaporation with a separation factor of ~ 100. These values are bettered only by high boiling hydrophobic cyanoborate ionic liquid based supported liquid membranes. Incorporation of a small molar percentage of Divinyl benzene and butyl acrylate causes a reduction in separation performance but is seen to maintain mechanical integrity for a longer period of time, thus allowing for structural membrane engineering and industrial scale up.

Our rapidly developing modern society challenges to scientific and engineering organizations in that many of the currently used technologies and prospective engineering innovations need to be directed in a more sustainable way. Therefore, materials science and sustainable engineering will continue to have important roles in five key thematic areas such as energy, transportation, housing, materials resources and health [1]. In parallel with the experimental efforts, computer-aided materials design is also an important factor in the fabrication of novel materials, to be applied in driving engineering innovations and urgent technological needs for achieving a sustainable society. The recent advent of metal-organic framework materials (MOFs), as new functional adsorbents has attracted the attention due to scientific interest in the creation of unprecedented regular nano-sized spaces and in the finding of novel phenomena, as well as commercial interest in their application for storage and separation. For MOFs the structural versatility of molecular chemistry has allowed the rational design and assembly of materials having novel topologies and exceptional host-guest properties that are important for urgent sustainable applications. Due to the regularity of MOF structures, in a computer simulation we are easily able to build structural models of MOFs that are very helpful to find new materials with desired characteristics.
The aim of this study is detailed theoretical analysis the adsorption of targeted molecules into selected nanoporous materials in order to accelerate the realization of novel materials, hand-in-hand with experiment. Here, our recent achievements have been reported. The high sorption ability for acetylene on specific MOF material was determined [2], using both different experimental measurements and first-principles calculations which ascribe to the double hydrogen bond support between the acidic acetylene proton and its acceptor basic site on the channel surface. The absorption of several chiral sulfoxides, which constitute an important class of biologically active compounds and therapeutic drugs, into the homochiral porous coordination polymer has been also investigated [3]. In collaboration with experimentalists the specific nanoporous material that selectively adsorbs CO with adaptable pores has been studied using first-principles calculations. The high selectivity of CO has been achieved from a mixture with nitrogen by both the local interaction between CO and accessible open metal sites and the modification of nanopore size [4].
REFERENCES
[1] D. Apelian, MRS Bulletin2012, 37, 318.
[2] R. Matsuda et al. Nature 436 (2005) 238.
[3] D. N. Dybtsev et al. Chem.-Euro. J. 16 (2010) 10348.
[4] H. Sato et al. Science 343 (2014) 167.

Water scarcity affects one in three people globally. Membranes are a key technology for water sustainability, for example wastewater reclamation and reuse. They also use less energy and no added chemicals, which makes their use more “green” compared to distillation and other separation methods. But current commercial membranes are susceptible to fouling, which manifests as a loss in permeability due to macromolecular adhesion on the membrane surface. Fouling lowers productivity and increases energy consumption and cost. We need membrane materials that offer excellent fouling resistance, along with high flux and selectivity. Here we report a new class of membrane materials using self-assembling zwitterion-containing polymers. Zwitterionic groups strongly resist biomacromolecular fouling due to their high affinity with water, which makes them favorable for membrane applications. Zwitterions are known to self-assemble into channel-type clusters of 0.6-2 nm in size. We have shown that within certain composition ranges, random copolymers of zwitterionic and hydrophobic monomers self-assemble to form bicontinuous networks of nanochannels. We have synthesized such copolymers and formed thin film composite membranes by coating them onto commercial ultrafiltration membrane supports. These membranes exhibit permeabilities as high as 21 L/m².h.bar, which can be further improved by better membrane manufacturing and processing methods. Based on the rejection of anionic dyes of varying sizes, they show size-based selectivity with a size cut-off around 1 nm. This pore size closely matches the size of the zwitterionic nanochannels, measured to be ~1.1-1.4 nm in diameter by transmission electron microscopy (TEM). We have also demonstrated the excellent fouling resistance performance of these membranes in parallel to a commercial membrane of comparable pore size. We expect these membranes to be promising candidates for various membrane and sustainable water applications.

Nanofiltration technology is being investigated as a cost-e#64256;ective and environmentally acceptable mechanism of sustaining industrial and public water systems. Nanofiber membranes are part of the family of filtration devices being used to remove inorganics and organics from water systems. This study investigates the use of the natural material, Opuntia ficus-indica (Ofi) cactus mucilage, as a tool for nanofiber membrane filtration. Mucilage is a natural, non-toxic, bio-compatible, biodegradable, inexpensive and abundant material. Mucilage is a clear colorless substance comprised of proteins, mono-saccharides, and polysaccharides. It also contains organic species which give it the capacity to interact with metals, cations and biological substances promoting flocculation for removing arsenic, bacteria, E. coli, and other particulates from drinking water. This natural material has the potential to be used as a sustainable method for water filtration and contaminant sensing. Therefore, mucilage nanofiber membranes were electrospun with volume ratios of polyvinyl alcohol (PVA) and polystyrene (PS) to mucilage comparing the interaction of non-polar solvents. Atomic Fluorescence Spectrometry (AFS) from PSAnalytical was used to evaluate electrospun nanofiber membranes made from volume ratios ranging from 30:70 to 70:30 of mucilage: polyvinyl alcohol, mucilage: polystyrene-D-limonene, and mucilage: polystyrene-toluene in different proportions. The mucilage nanofiber membranes were used as filtration devices for 50 ppb arsenic solutions. Arsenic, being a toxic substance, acts as a deadly poison in water systems and has plagued societal preservation for centuries. The total arsenic content in the samples were measured before and after treatment. Comparative tests were also performed using 1) coated and non-coated GVWP 0.22 µm and 0.45 µm filters from Millipore and 2) columnar flow through Pasteur glass pipets filled with 0.5 g of pre-washed sand from Fisher Scientific and 0.01 g of mucilage nanofibers. Results show mucilage: polystyrene nanofiber membrane filters were capable of removing arsenic from test solutions, in terms of the percentage of arsenic removed. These data elucidate that mucilage nanofiber membranes have the potential to serve as the basis for the next generation of economically sustainable filtration devices that make use of a natural non-toxic material for sustainable water systems.

Civilization on our planet took a sharp turn about 250 years ago, at the beginning of the industrial revolution, and has accelerated on that highway ever since. Arguably, its impact on humankind is equivalent to that of the invention of fire. The enormous consequences of industrial activity, positive and negative, could not have been anticipated then, but the bottom line today is that
per capita global consumption of energy is higher than ever, and demand for materials (relative to the year 1900) has increased by factors of 3 to 6000, depending on the element. Total population as well as those segments of the population doing the consuming, is also increasing. Now we speak (informally, thus far) of the Anthropocene, the first geological epoch in which human activity is deemed to have had an effect on the Earth&’s ecosystem. For how much longer can economic growth and demand for goods be sustained, and can the same human ingenuity that started the industrial revolution mitigate its effects?
In this talk I will address the meaning and definition of sustainable development, and explore the space at its intersection with materials science. Every human endeavor should be informed by sustainable development, because none of our material resources are in#64257;nite and only a few sources of energy are sustainable. The most common definition of sustainable development comes from the 1987 Brundtland report, “Our Common Future”, and states that “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” However, this is not a scientific definition, and essentially refers to economic development. Further, it requires that we know, or at least accurately estimate, what the needs of future generations will be. The immediate and direct connections between sustainable development and materials science include ef#64257;cient use of materials, materials life cycle assessment, replacement materials, energy-related materials, and water puri#64257;cation. I will highlight what MRS as a scientific society has been doing in the field of sustainable development, and suggest what future materials scientists should know about this field. From MRS&’s activities in sustainable development thus far, we have learned that there is nothing we do as humans to ensure our survival (food, water, materials, shelter, economy, health) that lies outside of its boundaries.

The National Science Foundation has a crosscutting initiative, Science, Engineering and Education for Sustainability, which supports research through a portfolio of programs. One of these programs, Sustainable Chemistry, Engineering and Materials (SusChEM), is particularly relevant to the materials community. This talk will provide an overview of sustainability and its significance to society and materials research. Topics covered in SusChEM and other NSF programs will be described in detail. These include, but are not limited to, utilization of earth-abundant elements; materials for food, water and energy sustainability; and designing products and devices for zero-waste.

Public outreach is often framed as a process of developing lesson plans with an aim of convincing the public to believe a series of facts and/or accept a specific viewpoint. These one-way patterns of communication, however, frequently fall short in at least two important ways. First, the public has many sources of information so getting the attention of a number of people is difficult. And second, the organizations that put together such programs are missing a major source of information that could help them to achieve their goals. Over the past several years museum professionals with the Nanoscale Informal Science Education Network (NISE Net) and scholars at Arizona State University&’s Center for Nanotechnology in Society have been developing techniques that go beyond this “linear model.” These techniques enable two way conversations in which members of the public learn about scientific achievements in a specific area and then build their own ideas of what they think a better future would like with them. What we have found is that the visitors to science museums in the United States are not only able to participate in constructive conversations, but that they are hungry for them. This talk will outline some of the lessons learned through this partnership and offer suggestions for how they can be implemented in other spheres.

Corporations are the greatest threat to the sustainability of our planet, and yet also promise to be the most effective means of resolving sustainability challenges. What shapes whether they do harm or do good? In this presentation, I focus on the role of a firm's stakeholders in influencing the firm's behaviors. In particular, I outline the role of firm-stakeholder relations in the business case for corporate social responsiblity, and I discuss several studies I've conducted that shed light on the limits of the business case for conditioning firms to engage in socially responsiblity practices.

In the last decades many efforts have been directed towards the development of efficient energy conversion systems using renewable energy resources. In the scenario, particular for automotive applications, the development of low temperature fuel cells plays a critical role towards the development of a sustainable hydrogen-based-economy. Alkaline fuel cells (AFCs) were the first low temperature fuel cells developed in the 1960s and mainly used for space program applications. Afterwards, mostly due to the electrolyte deterioration when in contact with CO₂, the interest in these systems has been shelved for many years. In parallel, the higher efficiencies and the advantage of using a polymer electrolyte membrane have driven the main research efforts towards the development of polymer electrolyte fuel cells (PEFCs). The main performance drops in PEFCs are caused by the cathodic electrode where the oxygen reduction reaction (ORR) takes place. For the development of competitive PEFCs the discovery of durable and cost-effective catalysts for the ORR is one of the most urgent requirements. State-of-the-art PEFC cathodes are based on Pt nanoparticles supported on high surface area carbons.¹ Despite the relatively good performance as cathode catalyst, Pt-supported on carbon suffers from corrosion stability, particularly due to carbon oxidation. Therefore, a growing interest is raising toward alternative, more stable support materials. In the present contribution alternative oxide-based supports have been investigated^2-5 and an insight into Pt/oxide novel catalysts will be presented.
In the last decade the development of alkaline conductive membrane has raised again R&D interest towards AFCs. Compared to PEFCs, AFCs make use of an electrolyte medium which is less corrosive with respect to a wider range of compounds, thus significantly broadening the range of possible stable and inexpensive electrode materials. Due to the above mentioned reasons, a broad range of materials has been investigated in recent years as alternative catalysts to noble metals. Particularly, perovskite oxides have shown the potentials of high electrocatalytic activity towards ORR in alkaline media. In this contribution the performance of different perovskites as ORR catalysts will be presented, unraveling the oxygen reduction mechanism for this novel class of materials.^6,7
The authors gratefully acknowledge: Swiss National Science Foundation (Ambizione Program), Swiss Competence Center for Energy Research (SCCER) Heat & Electricity Storage, and Umicore GmbH.
[1] E. Fabbri et al. ChemCatChem 6 (2014)1410-1418.
[2] A. Rabis et al. Phys. Chem.C 118 (2014) 11292-11302.
[3] E. Fabbri et al. Phys.Chem.Chem.Phys. (2014) DOI:10.1039/C4CP00238E.
[4] E. Fabbri et al. Chimia 68 (2014) 217-220.
[5] T. Binninger et al. J. Electrochem. Soc. 161 (2014) H121-H128.
[6] E. Fabbri et al. ChemElectroChem 1 (2014) 338-342.
[7] E. Fabbri et al. ACS Catalysis 4 (2014) 1061-1070.

Sustainable electricity generation technologies are highly variable, and energy storage has an important role in integrating them into the grid at large scale. Building this energy storage capacity has an energy cost, as with any manufacturing process. However, different energy storage technologies have different energy costs for manufacturing the same kilowatt-hour of storage capacity. Net energy analysis, a type of life cycle analysis, systematically examines the life-cycle energy costs of technologies such as energy storage. In this work, we apply net energy analysis to evaluate a regenerative hydrogen fuel cell (RHFC) as an energy storage system. To compare RHFC's to other storage technologies, we use the energy stored on invested (ESOI) ratio: the ratio of energy stored in the device over its lifetime to the energy required to build and operate the device. A device with a higher ESOI ratio provides the same service while consuming less energy during manufacture and operation, leaving the difference available for other productive uses. We present a model to determine the ESOI ratio of a RHFC system as a function of system properties such as storage capacity and fuel cell efficiency.
The ESOI ratio of our hypothetical RHFC system is similar to that of the best battery technology (Li-ion, ESOI = 10; Energy Env. Sci., 2013, 6, 1083), though still lower than those of pumped hydro (ESOI = 240) and compressed air (ESOI = 210). A sensitivity analysis highlights priorities for catalysis research in order to optimize the system's net energy performance: The most important technology advance for increasing the system's ESOI ratio is increasing the fuel cell lifetime to at least 20,000 h, and the electrolyzer lifetime to at least 50,000 h. In contrast, the ESOI ratio is only modestly sensitive to the efficiency of the electrolyzer and fuel cell, and to the embodied energy requirements for manufacturing these components. The system's energy-to-power ratio is also an important parameter. Although there is substantial uncertainty in the embodied energy values, uncertainty analysis indicates that on a net energy basis, a RHFC system can be competitive with Li-ion batteries even with higher-than-estimated embodied energy values. Finally, we illustrate the opportunities for further technology development to improve the net energy balance of RHFC's. For instance, in an RHFC system with an extended-life fuel cell (50,000 h) and electrolyzer (150,000 h) and an energy-to-power ratio of 10, the ESOI ratio would approach 80, well above that of any battery technology.

Core-shell ferrite materials can be utilized for thermochemical water-splitting process to achieve relatively stable hydrogen volume generation in multiple thermochemical cycles. Sol-gel derived ferrite nanoparticles can be further utilized for the preparation of core-shell nanoparticle morphologies. During sol-gel synthesis of core-shell morphology achieving monodispersion of ferrite nanoparticles pose significant technical challenge. As ferrite nanoparticles are magnetic by nature, while preparing the dispersion their agglomeration is unavoidable. To address this issue, we attempted to prepare monoparticulate dispersion of ferrite (e.g. NiFe₂O₄) nanoparticles, which were later subjected to in-situ zirconia coating following the sol-gel chemistries. Monoparticulate dispersion of ferrite nanoparticles were investigated in presence of non-ionic and ionic surfactants such as Pluronic P123, sodium dodecyl sulfate (SDS) and cetyltriammonium bromide (CTAB) whereas the effects of these surfactants on particle morphology were studied during controlled hydrolysis and condensation reactions of zirconium isopropoxide with water. The obtained ferrite/zirconia gels were aged and calcined at 600^oC. Transmission electron microscopy (TEM) revealed core-shell nanoparticle morphology whereas x-ray diffraction showed desired phase composition. These core-shell nanoparticles were loaded inside Inconel tubular reactor where multiple water-splitting and regeneration steps were performed at 900^o-1100^oC. These results indicated relatively stable H₂ volume generation during 10 consecutive thermochemical cycles. The thickness and porosity of ZrO₂ shell was found to depend on the type of surfactant used and optimum concentration of the surfactant and reactants employed. H₂ volume generation ability of the monoparticulate core-shell ferrite nanoparticles was further correlated with the thickness and porosity of ZrO₂ shell. Specific surface area (SSA) and porosity of core-shell nanoparticles were analyzed by BET surface area analyzer whereas grain growth was characterized by scanning electron microscopy (SEM) and TEM after thermochemical water-splitting reaction. Characterization of core-shell nanoparticles and the results obtained on H₂ volume generation with core-shell ferrite nanoparticles will be presented.

This talk will provide an overview of recent progress in the development of sustainable photocatalytic materials for solar-driven production of hydrogen from water. The emphasis will be recent realization of disorder-engineered titanium dioxide, starting with an introduction of the electronic band structure resulted from disorder incorporation. The method of making disorder-engineered titanium dioxide nanocrystals will be presented, followed by measurements of their structural, electronic, and optical properties. Photocatalysis experiments based on solar-driven hydrogen production using disorder-engineered titanium dioxide nanocrystals, that can absorb solar energy in both visible and infrared wavelength regions, will be summarized, followed by an analysis of the fundamental physics underlying increased photocatalytic efficiency of disorder-engineered titanium dioxide nanocrystals.

A Redox Flow Battery (RFB) possesses several key advantages that make this technology potentially well suited for large scale energy-storage applications. This is especially true of applications that require high energy-to-power requirements (i.e., multiple-hour discharge times at rated power) since the energy capacity can be increased by simply adding reactant solution without necessarily requiring (or negatively impacting) the power-delivery components. Despite this inherent scaling-factor advantage relative to conventional battery systems, the initial capital cost of flow batteries has been the major barrier to commercialization of RFB technology. Capital-cost targets for grid-scale energy storage are challenging; battery systems for major grid-scale applications must cost less ($/kWh) than those currently used for most portable or transportation applications. One attractive path to cost reduction is the development of RFB cells with substantially higher power densities than conventional RFB cells. United Technologies Research Center (UTRC) has developed and demonstrated high performance flow-battery cell stacks operating in complete Prototype RFB Systems. A summary of these results has been presented previously. Therefore, the focus of this talk will be on new materials that can potentially enable additional RFB-system cost reductions. This includes both advanced cell materials (e.g., electrodes, separators/membranes, bipolar plates) that can further improve the performance RFB cells, as well advanced reactant solutions. Key system-performance indices provide the basis for the formulation of key property requirements for these advanced materials. A brief review of the state-of-the-art of each these major materials will be included, along with their key properties. The major goal of this presentation is to help material developers identify potential opportunities to substantially improve RFB technology.
Acknowledgements
The author would like to thank his multiple colleagues at UTRC who have been an essential part of UTRC&’s advanced flow-battery team.

Sn₂Fe has been regarded as a promising candidate to replace presently dominating graphite anodes due to its low cost, environmental benignity and high theoretical capacity (804 mAh/g)¹. However, the electrochemical reaction mechanism of Sn₂Fe is not fully elucidated yet. It has been widely reported that Li-Sn alloys could be formed during lithiation of Sn₂Fe while Fe being extruded, whereas Fe is difficult to be detected^2,3. But there is a debate for the delithiation process, during which some researchers claimed that the “liberated” Fe particles would remain inert so that Sn₂Fe could not be re-created⁴, while others argued contrarily that Sn₂Fe could be reproduced upon delithiation². To have a comprehensive understanding of the reaction mechanism of this material, pure Sn₂Fe was prepared solvothermally by reducing SnCl₂ and FeCl₃ with NaBH₄; the reaction mechanism during the first two cycles has been thoroughly investigated through a variety of in-situ and ex-situ characterization techniques such as X-ray absorption spectroscopy (XAS), powder X-ray diffraction (XRD), pair-distribution function (PDF) analysis, etc. Our results confirmed that the Li-Sn alloys were formed during the lithiation process, so was the Fe phase; such a reaction is reversible upon delithiation and most of Sn₂Fe could be re-formed (but with a small portion of discrete Fe and Li-Sn alloys being inactive). During this reaction, the formation and dissolution of Fe were successfully identified by a combined analysis of synchrotron-based XRD, XAS and PDF techniques. This research is supported by DOE-EERE-BATT, DE-AC02-05CH11231 under Award Number 6807148, and by NYSERDA.
(1) Zhang, R.; Upreti, S.; Stanley Whittingham, M. Journal of The Electrochemical Society2011, 158, A1498.
(2) Yoon, S.; Lee, J.-M.; Kim, H.; Im, D.; Doo, S.-G.; Sohn, H.-J. Electrochimica Acta2009, 54, 2699.
(3) Chamas, M.; Sougrati, M.-T.; Reibel, C.; Lippens, P.-E. Chemistry of Materials2013, 25, 2410.
(4) Nwokeke, U. G.; Alcántara, R.; Tirado, J. L.; Stoyanova, R.; Yoncheva, M.; Zhecheva, E. Chemistry of Materials2010, 22, 2268.

Platinum-group metals supported and dispersed on highly reducible oxide surfaces are active catalysts for several reactions of industrial interest, including water-gas shift, selective CO oxidation, hydrocarbon reforming, low-temperature hydrogen/methanol oxidation, and oxygen reduction. Due to their high cost, there is an ongoing effort for reducing the amount of precious metal without affecting the device efficiency. In the context of polymer-electrolyte-membrane fuel cell electrodes, ultra-low loading Pt-ceria (CeO₂) systems are investigated as potential candidates for meeting the new national and international targets [1].
Density functional theory calculations are used to rationalise the enhanced reactivity displayed by these Pt-ceria systems and to characterise the active sites of new materials that minimise the Pt load by means of solid solutions. In particular, I will first focus on supported sub-nm Pt clusters and establish the role of cluster morphology in the thermodynamics and kinetics of surface processes relevant for reactivity: cluster mobility, charge transfers at the metal-oxide interface, reverse oxygen spillover, and oxygen vacancy formation [2,3]. I will then present a thermodynamics analysis that predicts the stability of specific Pt²⁺ and Pt⁴⁺ species in realistic reaction conditions, emphasising the key role played by O vacancies, surface steps and solid solutions [4]. The results will be discussed in the context of recent STM images and XPS data. The different reactivity of these sites towards hydrogen and methanol oxidation will be established and rationalised in terms of local electronic and morphological properties.
The calculated results allow for rationalising the available experimental data and identify correlations among the mechanism of reaction, thermodynamic efficiency, and local structure of the active sites, thus shedding light on the origins of the reactivity and stability of novel Pt/CeO2 materials for fuel-cell electrodes.
[1] A. Bruix et al., Angew. Chem. Int. Ed., in press.
[2] P. Ghosh, M. Farnesi Camellone, and S. Fabris, J. Phys. Chem. Letters (2013)
[3] F. R. Negreiros and S. Fabris, submitted (2014)
[4] M. Farnesi Camellone, F. R. Negreiros, and S. Fabris, submitted (2014)

Tungsten Oxide is still considered a promising candidate as photoanode for both, water splitting and CO₂ reduction. However, photocurrent densities obtained up to now are far away from the theoretical values according to its band gap (2.7 eV). The short diffusion length of the charge carriers limits the thickness of the WO₃ films and consequently its light absorbance. In this work, we present high crystal quality WO₃ films deposited by Pulse Laser Deposition (PLD) which reduces bulk recombinations through grain boundaries and increase diffusion lengths. Finally, a Al₂O₃ surface passivation was applied using Atomic Layer Deposition in order to diminish recombination at surface states and also the formation of peroxo-species.