Virtual Special Issue on Catalysis at the U.S. Department of Energy's

National Laboratories are home to many DOE Office of Science national scientific user ..... Current program interests include catalyst systems for con...
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Virtual Special Issue on Catalysis at the U.S. Department of Energy’s National Laboratories

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atalysis research at the U.S. Department of Energy’s (DOE’s) National Laboratories covers a wide range of research topics in heterogeneous catalysis, homogeneous/ molecular catalysis, biocatalysis, electrocatalysis, and surface science. Since much of the work at National Laboratories is funded by DOE, the research is largely focused on addressing DOE’s mission to ensure America’s security and prosperity by addressing its energy, environmental, and nuclear challenges through transformative science and technology solutions. The catalysis research carried out at the DOE National Laboratories ranges from very fundamental catalysis science, funded by DOE’s Office of Basic Energy Sciences (BES), to applied research and development (R&D) in areas such as biomass conversion to fuels and chemicals, fuel cells, and vehicle emission control with primary funding from DOE’s Office of Energy Efficiency and Renewable Energy. National Laboratories are home to many DOE Office of Science national scientific user facilities that provide researchers with the most advanced tools of modern science, including accelerators, colliders, supercomputers, light sources, and neutron sources, as well as facilities for studying the nanoworld and the terrestrial environment. National Laboratory research programs typically feature teams of researchers working closely together, often joining scientists from different disciplines to tackle scientific and technical problems using a variety of tools and techniques available at the DOE national scientific user facilities. Along with collaboration between National Laboratory scientists, interactions with university colleagues are common in National Laboratory catalysis R&D. In some cases, scientists have joint appointments at a university and a National Laboratory. This ACS Catalysis Virtual Special Issue {http://pubs.acs. org/page/accacs/vi/doe-national-labs} was motivated by Christopher Jones and Rhea Williams, who sent out the invitations to all of DOE’s National Laboratories where catalysis research is conducted. All manuscripts submitted went through the standard rigorous peer review required for publication in ACS Catalysis. A total of 29 papers are published in this virtual special issue, which features some of the recent catalysis research at 11 of DOE’s National Laboratories: Ames Laboratory (Ames), Argonne National Laboratory (ANL), Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL), Lawrence Livermore National Laboratory (LLNL), National Energy Technology Laboratory (NETL), National Renewable Energy Laboratory (NREL), Oak Ridge National Laboratory (ORNL), Pacific Northwest National Laboratory (PNNL), Sandia National Laboratory (SNL), and SLAC National Accelerator Laboratory (SLAC). In this preface, we briefly discuss the history and impact of catalysis research at these particular DOE National Laboratories, where the majority of catalysis research continues to be conducted. © XXXX American Chemical Society

AMES LABORATORY

The Ames Laboratory’s catalysis program has a tradition of research in homogeneous and heterogeneous catalysis that spans over four decades. Initially, investigations included the structure and performance of supported bimetallic catalysts by experimental and theoretical approaches,1 mechanisms of hydrodesulfurization of thiophenes and thiophene-related organometallic compounds over Mo/γ-Al2O3 and Re/γ-Al2O3 catalysts,2 and kinetics as well as mechanisms of oxidations by transition-metal catalysts, including those based on nonprecious metals such as iron.3,4 Over a decade ago, the program initiated a sustained effort in interfacial catalysis, toward bringing the best features of homogeneous and heterogeneous catalysis together by utilizing new possibilities for heterogenization of homogeneous catalysts onto solid supports. To this end, singlesite, multifunctionalized mesoporous catalysts with adjustable morphology and catalytic properties were constructed.5 Their importance lies in nanostructured three-dimensional (3D) topology, which can be characterized and rationally iterated to achieve the desired catalytic performance. These efforts led to the development of bifunctional mesoporous calcium silicate mixed oxide catalysts for the conversion of bio-based free fatty acid feedstocks into biodiesel, and subsequent founding of a startup company, Catilin, that brought this technology to the market. As demonstrated by the contributions to this issue, interfacial catalysis in 3D controlled environments continues to be the focus of the program, which, at present, consists of experts on the development of mesoporous and nanoporous materials,6 mechanistic and kinetic studies of organometallic asymmetric catalysis,7 and spectroscopic characterization by solid-state NMR.8 Ames Laboratory researchers use synthetic, spectroscopic, and theoretical tools to systematically study the fundamental interfacial interactions between selected active sites, mesoporous supports, reactants, and reaction media. This understanding is needed to create catalysts with the best selectivity and properties for efficient reductive transformations of energy-relevant molecules and biorenewable compounds under less forcing conditions. Signature areas of the program include the introduction of cooperativity via modification of support surfaces with organic moieties and the design of singlepot tandem multicatalytic systems. Targeted reactions include selective reductions of carbonyls (ketones, esters, acids, and amides) and phenolics through hydrogenation or hydroboration. Important insights are also provided by extensive collaboration with theorists and computational chemists in the Computational and Theoretical Chemistry Program in Ames Laboratory.

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ARGONNE NATIONAL LABORATORY Catalysis research at ANL started in the late 1970s on hydroformylation, highlighting the use of high pressure, in situ NMR for determining the reaction pathways for cobalt carbonyl catalysts.9−11 Successful use of high pressure NMR is now a routine tool in the catalysis community. At approximately the same time, there was also work on the use of zeolites that improved our understanding of methane conversion catalysis.12,13 In the early 1990s, the ANL heterogeneous catalysis effort concentrated on improvements in selectivity of refining and chemical production catalysts with the development of many of the early techniques employing in situ X-ray absorption spectroscopy at Argonne’s Advanced Photon Source (APS).14,15 Since the mid 2000s, ANL’s work has expanded to the use of in situ Raman spectroscopy and Atomic Layer Deposition (ALD) as a synthesis tool16,17 to better understand many new core−shell and alloy materials, primarily for oxidative dehydrogenation reactions systems. In parallel, in situ characterization of catalysts using the APS has been enhanced,18,19 starting out primarily in one APS sector and expanding to a suite of sectors17−20 dedicated primarily to catalysis. In 2009, a DOE Energy Frontier Research Center, the Institute for Atom-Efficient Chemical Transformations (IACT), was funded bringing together key researchers from ANL, Northwestern University, Purdue University, the University of Wisconsin-Madison and BNL. IACT worked on numerous projects aimed at understanding the fundamental principles for the conversion of biomass feedstocks to fuels in a group of 20 principal investigators and collaborators in advanced material synthesis, in situ characterization, computational modeling and reaction mechanisms. Equal weighting was given to all four key research components, resulting in an integrated approach to catalysis research uncommon within many programs at the time. The interactive IACT team mentored over 100 graduate students and post docs.20−22 IACT mapped out the kinetics and mechanisms of complex biomass conversion pathways by integrated collaborations between theory and experiment. IACT coupled the synthesis of new catalytic materials with an experimental and theoretical understanding of how these sites efficiently affected chemical transformations at both the atomic and electronic level. These insights provided evidence for the utility of catalyst design and synthesis guided by theoretically predicted high-performance structures, rather than empirical discovery methods.

for fuel cell electrocatalysts with reduced noble metal content using active platinum monolayers as shells supported on lower cost cores. BNL scientists developed practical, low-precious metal group (PGM) content core−shell catalysts with high stability and efficiency for both cathode (oxygen reduction) and anode (hydrogen oxidation) reactions.29,30 BNL catalysis research efforts in heterogeneous catalysis and electrocatalysis have exploited unique on-site capabilities for in situ characterization of catalytic materials at the National Synchrotron Light Source (NSLS). In the 1990s, time-resolved X-ray diffraction (XRD) was developed to study the growth of zeolites and the evolution of catalysts under a wide range of temperatures (from 50 °C to 900 °C) and pressures (≤50 atm).31 Facilities have been developed for a range of in situ techniques: X-ray absorption fine structure (XAFS), pair-distribution function (PDF), and combined methods such as XAFS with XRD and XAFS with infrared spectroscopy (XAFS/IR). Scientists from BNL, Columbia and Yeshiva Universities have sponsored the Synchrotron Catalysis Consortium (SCC), a unique initiative to enhance the catalysis community’s use of synchrotron methods.32 Scientists are currently transitioning BNL capabilities for advanced catalytic research from NSLS to NSLS II a recently operational synchrotron with world-leading brightnessand exploiting new in situ nanoscale imaging capabilities at the Center for Functional Nanomaterials (CFN).

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LAWRENCE BERKELEY NATIONAL LABORATORY In the early 1970s, catalysis research at LBNL started with Alex Bell and Gabor Somorjai. Following his retirement from Mobil Oil, Heinz Heinemann joined LBNL, and research expanded to technologically important catalysis,33 in addition to the development of instrumentation in the fields of spectroscopy and low-energy electron diffraction of model single-crystal catalysts, and the development of other spectroscopic techniques such as X-ray photoelectron spectroscopy and sum frequency generation vibrational spectroscopy.34 The scope was later expanded to include the following: the synthesis of organic, organometallic, and inorganic compounds;35,36 the study of new chemical reactions and the reactive intermediates involved in homogeneous catalysis, supramolecular chemistry, and organic synthesis;37 development of novel instrumentation to study catalysts under reaction conditions on atomic and molecular scales;38 and detailed structural and mechanistic characterization and modeling of kinetic and transport processes in catalytic processes relevant to oil refining and petrochemical synthesis.39 In the 1990s, the research further expanded to include synthesis and catalyst characterization under reaction conditions with new instruments developed at LBNL, including various reactors that could study surfaces at low pressures and carry out reactions at high pressures and solid/liquid interfaces. With the rise of nanomaterial science, the catalysis research expanded to include nanomaterials, synthesis of nanoparticles of transition metals, bimetallics, oxides, mesoporous, microporous, and oxide/metal interfaces as important areas to the control of catalytic selectivity and resistance to deactivation. Recent new research areas include metal−organic frameworks,40 propane dehydrogenation, tandem catalysis and synthesis of core−shell and multicomponent nanocatalysts41 and enzyme catalysis.42 Currently, there are ∼75 people working in the catalysis program, mostly supported by DOE. This group represents the core of the chemical engineering approach to catalysis research in heterogeneous catalysis,43,44 the synthesis of nanoparticles

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BROOKHAVEN NATIONAL LABORATORY Since the early 1990s, BNL chemists have actively pursued research in heterogeneous catalysis and electrocatalysis, with a focus on energy conversion, particularly catalysis for alternative pathways in fuel synthesis and use. In heterogeneous catalysis, studies have demonstrated the important role that metal-oxide and metal-carbide interfaces play in the water−gas shift reaction, CO oxidation and in the conversion of CO2 to methanol.23−25 This work has led to novel designs of model and powder catalysts.26,27 Size-selected deposition has been employed to prepare supported catalysts that can be used to explore fundamental aspects of catalyst size-effects, clustersupport interactions, and reaction mechanisms of cluster materials, for instance for dissociation and reduction/oxidation reactions.28 In electrocatalysis, basic research in the 1990s on the structure and activity of metal surface layers led to concepts 3228

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biological catalysis research at NREL over the last 20 years has spanned from atomistic-scale modeling to pilot-scale operation and has been focused in three major areas: biomass conversion, solar water splitting, and electrochemical hydrogen production and conversion. The National Bioenergy Center at NREL is dedicated to developing bioenergy technologies that transform the marketplace by targeting both fuels and valuable co-products, and catalysis plays a central role in achieving this goal. For the thermochemical conversion of biomass, initial research efforts targeted the production of ethanol via biomass gasification, followed by mixed alcohol synthesis over K-CoMoSx catalysts. This work resulted in a modified K-CoMoSx synthetic method that improved activity and alcohol selectivity, while decreasing synthetic rigor, and elucidated the deactivation pathway for sulfided CoMo catalysts.58 In addition, in order to improve the carbon efficiency to finished fuel products, NREL developed a fluidizable, nickel-based steam reforming catalyst (Ni/Mg/K/αAl2O3) to convert tars and hydrocarbons formed during biomass gasification into additional syngas, and fundamentally investigated the kinetics, deactivation mechanisms, and regeneration of this catalyst.59 In 2012, these catalytic materials were utilized in an integrated pilot-scale system to demonstrate the conversion of biomass to ethanol. After 2012, attention shifted from ethanol to drop-in hydrocarbon fuels, produced via either gasification or pyrolysis. For the gasification pathway, recent NREL work has demonstrated that a copper-modified BEA zeolite can catalyze the low-temperature homologation of dimethyl ether, forming primarily branched C4−C8 hydrocarbons with minimal selectivity to aromatics due to activation and incorporation of cofed H2,60 and the olefins from this process can be coupled to produce jet fuel range products. For pyrolysis, vapor-phase upgrading catalyst development has been focused on both zeolite61 and nonzeolite materials (including supported noble metals,62 metal carbides,63 and metal phosphides), with specific emphasis on understanding how different biomass functionalities interact with the catalytic surfaces, so that catalytic materials with improved carbon efficiency and control over product distribution can be designed. Significant research has been conducted in the biocatalysis space, with a specific emphasis on understanding the catalytic mechanisms of cellulase and hemicellulase enzymes.64 In addition, whole-cell ethanologenic biocatalysts have been engineered to rapidly convert the broad range of pentose and hexose sugars found in lignocellulosic hydrolysate, and these strains are now being licensed for large-scale ethanol manufacturing. More recently, both enzyme and whole-cell biocatalysts are being pursued actively at NREL to produce drop-in replacement hydrocarbon fuels from sugars and to convert lignin-derived compounds to value-added chemicals.65 In the chemical catalysis space, multiple efforts have been pursued at NREL for several decades to depolymerize lignin to low-molecular-weight aromatic compounds, with emphasis on homogeneous alkaline catalysis and, as exemplified in this issue, with novel heterogeneous catalysts based on hydrotalcites.66 For future biorefinery applications, substantial efforts at NREL are now being placed on designing highly active and robust catalysts for upgrading biologically derived products to fuels and value-added chemicals. NREL is known for high-efficiency semiconductor-based solar water splitting,67 which requires minimizing kinetic overpotential losses by incorporating active water reduction

and model catalysts in the Molecular Foundry (which utilizes characterization techniques under reaction conditions), the LBNL’s Advanced Light Source (ALS) and Electron Microscope Center facilities for research of catalytic materials and catalytic processes, and catalysis study in electrochemistry for energy storage (including lithium batteries).

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LAWRENCE LIVERMORE NATIONAL LABORATORY The Lawrence Livermore National Laboratory has developed a unique nanoporous bulk materials library, mainly driven by the needs of its high-energy-density physics program. Historic milestones include the discovery of polymer-derived carbon aerogels in the 1980s,45 the recent development of monolithic graphene and carbon nanotube macro assemblies,46 and the development of various bulk nanoporous metals47 and metal oxides.48−50 Many of these materials have great potential in the field of catalysis. For example, carbon aerogels and their nanocarbon relatives have become a mainstream materials platform for electrocatalysis, and LLNL’s contributions in the field of nanoporous dilute alloy catalysts based on gold51 have culminated in a new DOE Energy Frontier Research Center, Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC), led by Harvard University. The center’s mission is to develop a fundamental understanding of how to design and use novel mesoporous catalyst architectures for sustainable conversion and production of chemicals. As we achieve a better understanding of the active sites in these materials, design principles can be developed for other dilute alloy catalysts. LLNL is leading the materials development and characterization focus area pillar, and future developments will be driven by LLNL’s expertise in surface functionalization and additive micromanufacturing techniques,53 which enable realization of engineered hierarchical porous architectures for applications that currently are limited by mass transport.

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NATIONAL ENERGY TECHNOLOGY LABORATORY NETL was designated as a DOE National Laboratory in 1999, but has been a federal research and development center since the establishment of the Pittsburgh Experiment Station in 1910 by the U.S. Bureau of Mines.54 Catalysis research on synthetic fuels production was initiated at the Pittsburgh campus in the mid-1920s55 and continues today. Fuels-related catalysis at the Morgantown facility started in the mid-1940s with the establishment of the Synthesis Gas Production Laboratory.54 Over the past 90 years, catalysis research at these two sites has focused on synthesis gas chemistry, fuel processing, mechanistic chemistry, and catalyst characterization.56 Recent catalyst efforts at NETL focus on the use of atomistic-scale computation in conjunction with experiments, as well as the development of multiscale models to predict catalyst performance in large-scale chemical processes. Current program interests include catalyst systems for converting CO2 emissions to fuels and chemicals, photocatalysts for water remediation, fuel production in catalytic membrane reactors, and catalytically active oxygen carriers for converting fuel to power and heat.57

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NATIONAL RENEWABLE ENERGY LABORATORY The mission of the National Renewable Energy Laboratory is the development of clean energy and energy efficiency technologies, with special emphasis on bringing them to the cusp of commercialization by bridging the gap between fundamental and applied science. Accordingly, chemical and 3229

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The NNI also led to the creation of the Center for Nanophase Materials Sciences (CNMS) at ORNL, which included research on catalysis by functionalized carbon materials.80 Researchers at ORNL are involved in two catalysis-related Energy Frontier Research Centers, namely, the Fluid Interface Reactions, Structures and Transport (FIRST) Center, which includes electrocatalysis at a fluid/ solid interface and investigating proton coupled reactions such as oxygen and CO2 reduction, and also the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME) led by Georgia Tech. The Critical Materials Institute included development of new catalysts based on cerium oxide as a route to mitigate production costs of the scarcer rare-earth elements. ORNL has a strong history of applied research targeted at emissions control catalysis and the development of techniques to study catalysts under conditions relevant to their in-use environments. This includes focused investigations on the surface chemistry of a Pt/K/Al2O3 catalyst under simulated exhaust conditions,81 probing studies of the intracatalytic reactions,82 identifying the influence of ceria for NOx storagereduction catalysis,83 and, more recently, transferring knowledge from the fundamental side of ORNL research to application-based studies. Recent work from ORNL shows that single Pt atoms, supported on inert alumina, are remarkable catalysts for both CO and NO oxidation while single supported Pd atoms do not catalyze NO oxidation. Based on density functional theory (DFT) modeling and spectroscopic studies, ORNL has shown that these reactions occur via carbonate (or nitrate) intermediates.84 In addition to emission related activities, ORNL has been active in catalytic conversion of biomass to commodity chemicals and fuels. Catalytic conversion of ethanol to hydrocarbon blend-stock has been shown to proceed via hydrocarbon pool type pathway and an endothermic dehydration to ethylene (which is believed to be the first step) is not necessary. Catalysis research at ORNL and in the larger catalysis community have benefited from many facilities and instrumentation available at ORNL. Research in emission controls, which dates back to the 1990s, is primarily performed in an ORNL user center: the Fuels, Engines and Emissions Research Center (FEERC). The CNMS has hosted more than 200 external users from some 50 institutions around the United States, who have performed experiments specifically related to catalysis and utilized a suite of capabilities available at the CNMS. ORNL is home to high-resolution, aberrationcorrected microscopes that permit atomically resolved images of catalysts at variable temperatures and under simulated reaction environments. Collaborative efforts with external users, for example, have led to imaging of single Pt atoms anchored to FeOx catalysts with extremely high atom efficiency85 and to unraveling the structures of nonprecious metal catalysts for oxygen reduction reactions. ORNL’s Spallation Neutron Source is now in operation with several beamlines available for general user research, some of which are capable of in situ neutron scattering experiments. The newly commissioned VISION instrument for inelastic neutron (vibrational) scattering has been used to demonstrate the chemical reaction of CO2 with a catalyst. A combination of neutron powder diffraction and pair distribution function presents a powerful tool for catalyst structure that has been used, for example, to differentiate transition-metal nitride structural polytypes and determine the

and oxidation catalysts. Traditionally, noble-metal catalysts are used to accelerate these gas-evolving half-reactions, which can limit scalability of such technologies. Replacing heterogeneous noble-metal catalysts with homogeneous molecular catalysts is ideal for terawatt-scale systems, with regard to both cost and resource availability, and NREL has been actively investigating Earth-abundant molecular catalysts.68 Recently, NREL successfully coupled an Earth-abundant metal-based molecular catalyst with p-GaInP2,69 which is a Group III−V semiconductor that is the interfacial component in high solar-to-hydrogen efficiency photoelectrochemical water-splitting systems. Furthermore, NREL has been developing Earth-abundant semiconductor photoanodes as alternatives to Group III−V materials for the challenging water oxidation reaction. Since 2010, NREL has been active in electrocatalysis research, with contributions including the development of ex situ and device testing protocols, and the structural and performance characterizations of nanostructured catalysts.70 Extended surfaces have improved the site-specific activities of platinum, notably Pt−Ni and Pt−Co in fuel cell applications,71 and iridium (Ir−Ni and Ir−Co) in renewable electrolysis. Investigations initially focused on galvanic displacement as a synthesis approach to improve catalyst surface areas; these efforts have more recently shifted to atomic layer deposition and device implementation.

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OAK RIDGE NATIONAL LABORATORY ORNL has a long history of catalysis and surface chemistry research. Current research funded by DOE ranges from fundamental to targeted research. Fundamental research started in the 1980s with the initial focus on surface chemistry and the use of low energy ion scattering as a probe of surface structure, which eventually led to the development of the ability to image the surface unit cell.72 Later on, the effort was expanded to include the surface chemistry of mercaptans and sulfur heterocyclic compounds on single-crystal metal surfaces and surface chemistry of CeO2 surfaces.73 An award from the National Nanoscience Initiative (NNI) expanded the effort into research in high-surface-area catalysis by gold, including support effects and experimental and theoretical work on well-defined gold clusters.74 This effort brought a strong component in catalyst synthesis, leading to new catalysts and synthetic methods. Today, the focus is on the investigation of catalysis by oxides including the role of surface structure on catalytic selectivity by faceted CeO2 and perovskite catalysts such as those discussed in the article by Dai et al. in the current virtual issue. The focus is on identifying the basis for selectivity in reactions of oxygenates, including small alcohols and organic acids.75 Computation is integrated with experimental spectroscopies to identify bonding structures and reaction pathways.76 Researchers at ORNL also investigated fundamental aspects of hydrogen transfer reactions related to coal liquefaction and upgrading. Specifically, the impact of restricted mass transport and pore confinement on hydrogen transfer reactions77 and the role of oxygen functional groups in cross-linking reactions of model compounds representative of low-rank coals.78 Solidstate NMR was used to determine the chemical nature of reactive sites and to quantitatively count reactive sites in coal through a novel 13C/14C labeling experiment. The fundamental studies on oxygen functional groups were expanded to the role of oxygen functional groups in the thermochemical conversion of lignin.79 New insights were gained into the reaction pathways for lignin degradation under fast pyrolysis conditions. 3230

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began to focus on the problem of lean-NOx emission control. This R&D, with much of it sponsored by the Department of Energy’s Vehicle Technology Program, has played a central role in the very recent successful commercialization of two new nanomaterials-based catalytic emission control technologies for diesel-powered vehicles: the NOx storage/reduction (NSR) catalysts,94 and the selective catalytic reduction (SCR) with ammonia using metal-exchanged zeolites. The NSR was first used in the United States on the 2007 Dodge Ram pickup. PNNL R&D on the zeolite-based catalysts for ammonia SCR (including the first open-literature publication on the nowcommercial Cu/SSZ-13 catalysts)95 included some studies of the hydrothermal stability and sensitivity to sulfur of the catalysts used on GM Duromax and Ford pick-up trucks. Research in molecular catalysis at PNNL has focused on the role of hydrogen and metal hydrides in catalytic reactions. Early efforts in the 1980s and 1990s focused on fundamental studies of organic and metal-mediated reactions that are important in coal chemistry. Much of that work involved detailed studies of the kinetics of hydrogen atom transfer reactions to or from organic compounds, including studies of hydrogen atom transfer reactions from metal hydrides.96 Those studies provided an understanding of the factors influencing the rates of M−H bond homolytic cleavage. Later studies investigated the factors that influence S−H bond cleavage in molecular molybdenum sulfur complexes that are pertinent to hydrodesulfurization reactions.97 Fundamental studies on the thermodynamic hydricity of metal hydride complexes provided insights that led to a molecular cobalt hydride complex that hydrogenates CO2, producing formate at exceptionally fast rates, rivaling the reactivity of precious metals.98 Recent efforts at PNNL on sustainable energy led to a focus on design of molecular electrocatalysts for conversions between electrical and chemical energy in the Center for Molecular Electrocatalysis, an Energy Frontier Research Center. Multiproton, multielectron reactions that are critical for energy storage and delivery require precise delivery or removal of protons. Using pendant amines as proton relays,99 a concept introduced by DuBois, accelerates the rates of hydrogen production by proton reduction,100 as well as the oxidation of hydrogen.101 Nickel electrocatalysts for production of H2 have shown turnover frequencies (TOFs) higher than those of the [FeFe]-hydrogenase in nature,102 and recent improvements have led to catalysts with TOFs in the range of 107 s−1.103 The fast rates are accompanied in many cases by high overpotentials, and lowering the overpotential is the focus of current efforts. In recognition of the extensive critical mass of catalysis R&D at PNNL, the Institute for Interfacial Catalysis (IIC) was formed in 2005, with Prof. J.M. “Mike” White as its first director. In May 2011, Prof. Johannes Lercher became the second Director of the IIC, and it was renamed the Institute for Integrated Catalysis, reflecting the merging of different subfields of catalysis science and engineering. The IIC has become the largest nonindustrial catalysis R&D organization in the United States, with >100 scientists carrying out catalysis studies that span from basic to applied research.

Co and Mo content of octahedral and trigonal sites of Co−Mo nitrides.86

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PACIFIC NORTHWEST NATIONAL LABORATORY Catalysis research at PNNL was initiated in the mid-1970s for the development and application of novel thermal, chemical, and biological processes that convert biomass to industrial and consumer products, fuels, and energy. A distinctive feature of PNNL’s research in these areas has been the development of novel catalyst materials and catalytic processes that convert sugars and organic acids to much higher value commodity and specialty chemicals. These products typically have a higher market value than biomass-derived fuel or energy, and the current worldwide marketplace is very promising. Among the achievements are the development of the Thermochemical Environmental Energy System (TEES) that converts wet organic residues to medium-BTU fuel gas (methane and carbon dioxide);87 groundbreaking work in developing a patented catalytic process that upgrades levulinic acid to methyltetrahydrofuran;88 and process development for the synthesis of propylene glycol from renewable sources (PGRS). PGRS is a catalytic process that offers an environmentally friendly, commercially viable method for converting plantbased, seed-oil-derived glycerol, sugars, or sugar alcohols to propylene glycol. Furthermore, PGRS is economically competitive with petroleum-based methods and results in up to a 61% reduction in greenhouse gas emissions. In 2006, the technology was licensed to ADM, which designed, engineered, and commissioned a new 100 000 metric-ton-per-year production facility in Decatur, IL. Catalysis research at PNNL expanded in the early 1990s as part of the establishment of the Environmental Molecular Science Laboratory (EMSL), which is a DOE user facility. EMSL was opened in 1997 to provide integrated experimental and computational resources for discovery and technological innovation. Catalysis research and related tools were built into EMSL’s foundation. State-of-the-art experimental and theoretical facilities include nuclear magnetic resonance (NMR) spectroscopy, a variety of microscopy techniques such as ultrahigh-resolution (aberration-corrected) transmission electron microscopy, and computational tools (NWChem) specially designed for high-performance computational chemistry on EMSL’s multiprocessor supercomputers. Highlights from the catalysis science carried out in EMSL include the following: science discoveries that provide the insights necessary for the development of a particularly effective method to convert glucose, which is nature’s abundant sugar, to hydroxymethylfurfural, which is a chemical that can be used as a feedstock for products currently made from petroleum;89 identification of Al atoms with 5-fold bonding coordination, which provided a molecular-level view of bonding interactions of Pt in alumina-supported Pt catalysts and, correspondingly, to strategies for improving Pt dispersion and stability;90 and development of a suite of advanced surface science tools to investigate catalysis on model surfaces.91 In the mid-1990s, research in process intensification (e.g., catalysis carried out in microchannel reactors)92,93 was pioneered at PNNL, ultimately leading to the formation of the start-up company Velocys, which is now traded in the London stock market and continues to focus on the commercialization of microchannel reactors for the smallscale conversion of biomass and fossil feedstocks to fuels. Around this same time, considerable new R&D focus at PNNL

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SANDIA NATIONAL LABORATORY Catalysis research at Sandia National Laboratories encompasses many chemistries and strategies to address a broad spectrum of energy-related topics. Heterogeneous catalysis has historically been prominent, with projects on catalytic combustion, leanburn NOx catalysis, and photocatalytic water purification. An 3231

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Center for Artificial Photosynthesis (JCAP) solar fuels hub, significant activity is being established with the goal of searching for electrochemical CO/CO2 reduction catalysts.

important development was an elementary reaction mechanism of catalytic hydrogen combustion that predicted the ignition and time-dependent reaction of H2/O2 mixtures on Pt surfaces.104 This work was later extended to partial oxidation of hydrocarbons to produce syngas.105 Sandia researchers also made important contributions to the development of catalysts and additives for reversible hydrogen storage in metal hydrides. These render the solid-state reaction reversible and increases the rate of H2 release and uptake, as demonstrated for bulk and nanoscale Ti-doped NaAlH4106−108 A new direction in heterogeneous catalysts was recently established when catalysts based on nanoporous metal−organic frameworks were found to catalyze the hydrogenolysis of aryl−ether bonds, which are relevant to lignin degradation (featured in this issue).109 Catalysts for fuel cells and electrolyzers are another focus of research. Several cost-effective nanoscale electrocatalysts for mechanistically complex reactions have been developed. These include electrodeposited MnOx/PEDOT composites that outperform the more-expensive Pt/C benchmark catalysts in alkaline electrolyte. This is due to their synergistic charge transfer capabilities, attained by coelectrodepositing MnOx with a conductive polymer while simultaneously achieving intimate substrate contact.110 The first organometallic Zn complex to facilitate the electrochemical conversion of CO2 to CO was also developed. This homogeneous catalyst lowers the overpotential required for CO2 reduction by ∼0.6 V.111 This transformation is achieved at a glassy carbon electrode (GCE), which is decidedly more desirable than the expensive Pt or Pd alternatives commonly used to accomplish electrocatalysis of this nature.

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SUMMARY Overall, this Virtual Special Issue of ACS Catalysis touches on the wide range of research topics in heterogeneous catalysis, homogeneous/molecular catalysis, electrocatalysis, and surface science being carried out at the U.S. Department of Energy’s National Laboratories. Marek Pruski Aaron D. Sadow Igor I. Slowing Ames Laboratory Christopher L. Marshall Peter Stair Argonne National Laboratory Jose Rodriguez Alex Harris Brookhaven National Laboratory Gabor A. Somorjai Lawrence Berkeley National Laboratory Juergen Biener Lawrence Livermore National Laboratory Christopher Matranga Congjun Wang National Energy Technology Laboratory Joshua A. Schaidle Gregg T. Beckham Daniel A. Ruddy Todd Deutsch Shaun M. Alia National Renewable Energy Laboratory Chaitanya Narula Steve Overbury Todd Toops Oak Ridge National Laboratory R. Morris Bullock Charles H. F. Peden Yong Wang* Pacific Northwest National Laboratory Mark D. Allendorf Sandia National Laboratory Jens Nørskov Thomas Bligaard SLAC National Accelerator Laboratory

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SLAC NATIONAL ACCELERATOR LABORATORY Catalysis research has deep roots at the SLAC National Accelerator Laboratory. The Stanford Synchrotron Radiation Lightsource user facility has over the past decades attracted a large number of catalysis researchers. Studies were often focusing on the characterization of catalytic materials, the development of surface-sensitive X-ray characterization techniques, and the investigation of ultrafast phenomena in molecular catalysts. In 2010, the SUNCAT Center for Interface Science and Catalysis was inaugurated as a partnership between Stanford University and SLAC National Accelerator Laboratory with Professor Jens Nørskov as director. The Center integrates the heterogeneous catalysis effort that occurs in the laboratory today. The research focuses on exploring the challenges associated with the atomic-scale design of catalysts for chemical transformations relevant for energy conversion and storage. This exploration is carried out in a theory-driven effort, which is closely integrated with experimental characterization, atomically controlled synthesis, and testing of catalyst materials. By combining experimental and theoretical methods, the objective is to develop a quantitative description of chemical processes at the solid/gas and solid/liquid interface. The goal is to identify the factors controlling the catalytic properties of solid surfaces and use these to tailor new catalysts.112−114 The approach is to integrate electronic structure theory and kinetic modeling115 with X-ray free electron laser studies,116,117 operando118 and in situ characterization techniques,119 atomic-scale controlled synthesis of catalysts,120 compounds,121 and functional nanostructures,122,123 and finally testing under realistic process conditions.124−127 The reactions studied vary from syngas utilization to electrochemical HER, OER, ORR, and ammonia synthesis. With SUNCAT’s continued participation in the Joint

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

Views expressed in this editorial are those of the authors and are not necessarily the views of the ACS.

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ACKNOWLEDGMENTS The authors are grateful to the U.S. Department of Energy’s Office of Basic Energy Sciences and the Office of Energy 3232

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