Advances in Cathode Materials for Solid Oxide Fuel Cells: Complex Oxides without Alkaline Earth Metal Elements

Solid oxide fuel cells (SOFCs) represent one of the cleanest and most efficient options for the direct conversion of a wide variety of fuels to electricity. For example, SOFCs powered by natural gas are ideally suited for distributed power generation. However, the commercialization of SOFC technologies hinges on breakthroughs in materials development to dramatically reduce the cost while enhancing performance and durability. One of the critical obstacles to achieving high‐performance SOFC systems is the cathodes for oxygen reduction reaction (ORR), which perform poorly at low temperatures and degrade over time under operating conditions. Here a comprehensive review of the latest advances in the development of SOFC cathodes is presented: complex oxides without alkaline earth metal elements (because these elements could be vulnerable to phase segregation and contaminant poisoning). Various strategies are discussed for enhancing ORR activity while minimizing the effect of contaminant on electrode durability. Furthermore, some of the critical challenges are briefly highlighted and the prospects for future‐generation SOFC cathodes are discussed. A good understanding of the latest advances and remaining challenges in searching for highly active SOFC cathodes with robust tolerance to contaminants may provide useful guidance for the rational design of new materials and structures for commercially viable SOFC technologies.     

Recent progress in electrodes for microbial fuel cells

The performance and cost of electrodes are the most important aspects in the design of microbial fuel cell (MFC) reactors. A wide range of electrode materials and configurations have been tested and developed in recent years to improve MFC performance and lower material cost. As well, anodic electrode surface modifications have been widely used to improve bacterial adhesion and electron transfer from bacteria to the electrode surface. In this paper, a review of recent advances in electrode material and a configuration of both the anode and cathode in MFCs are provided. The advantages and drawbacks of these electrodes, in terms of their conductivity, surface properties, biocompatibility, and cost are analyzed, and the modification methods for the anodic electrode are summarized. Finally, to achieve improvements and the commercial use of MFCs, the challenges and prospects of future electrode development are briefly discussed.     

Electron transfer mechanisms, new applications, and performance of biocathode microbial fuel cells

Broad application of microbial fuel cells (MFCs) requires low cost and high operational sustainability. Microbial-cathode MFCs, or cathodes using only bacterial catalysts (biocathodes), can satisfy these demands and have gained considerable attention in recent years. Achievements with biocathodes over the past 3-4 years have been particularly impressive not only with respect to the biological aspects but also the system-wide considerations related to electrode materials and solution chemistry. The versatility of biocathodes enables us to use not only oxygen but also contaminants as possible electron acceptors, allowing nutrient removal and bioremediation in conjunction with electricity generation. Moreover, biocathodes create opportunities to convert electrical current into microbially generated reduced products. While many new experimental results with biocathodes have been reported, we are still in the infancy of their engineering development. This review highlights the opportunities, limits, and challenges of biocathodes.     

Recent Advances in Perovskite Oxides as Electrode Materials for Nonaqueous Lithium–Oxygen Batteries

Lithium–oxygen batteries are considered the next‐generation power sources for many applications. The commercialization of this technology, however, is hindered by a variety of technical hurdles, including low obtainable capacity, poor energy efficiency, and limited cycle life of the electrodes, especially the cathode (or oxygen) electrode. During the last decade, tremendous efforts have been devoted to the development of new cathode materials. Among them, perovskite oxides have attracted much attention due to the extraordinary tunability of their compositions, structures, and functionalities (e.g., high electrical conductivities and catalytic activities), demonstrating the potential to achieve superior battery performance. This article focuses on the recent advances of perovskite oxides as the electrode materials in nonaqueous lithium–oxygen batteries. The electrochemical mechanisms of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the surface of perovskite oxides are first summarized. Then, the effect of nanostructure and morphology on ORR and OER activities is reviewed, from nanoparticles to hierarchical porous structures. Moreover, perovskite‐oxide‐based composite electrodes are discussed, highlighting the enhancement in electrical conductivities, catalytic activities, and durability under realistic operating conditions. Finally, the remaining challenges and new directions for achieving rational design of perovskite oxides for nonaqueous lithium–oxygen batteries are outlined and discussed.     

Prospect and Reality of Ni‐Rich Cathode for Commercialization

The layered nickel‐rich cathode materials are considered as promising cathode materials for lithium‐ion batteries (LIBs) due to their high reversible capacity and low cost. However, several significant challenges, such as the unstable powder properties and limited electrode density, hindered the practical application of the nickel‐rich cathode materials with the nickel content over 80%. Herein, important stability issues and in‐depth understanding of the nickel‐rich cathode materials on the basis of the industrial electrode fabrication condition for the commercialization of the nickel‐rich cathode materials are reviewed. A variety of factors threatening the battery safety such as the powder properties, thermal/structural stability are systemically investigated from a material point of view. Furthermore, recent efforts for enhancing the electrochemical stability of the nickel‐rich cathode materials are summarized. More importantly, critical key parameters that should be considered for the high energy LIBs at an electrode level are intensively addressed for the first time. Current electrode fabrication condition has a difficulty in increasing the energy density of the battery. Finally, light is shed on the perspectives for the future research direction of the nickel‐rich cathode materials with its technical challenges in current state by the practical aspect.     

Recent Progress in Biomass‐Derived Electrode Materials for High Volumetric Performance Supercapacitors

Tremendous efforts have been spent on the development of electrical energy storage (EES) systems with high volumetric performance in the past few years due to the evergrowing demand of miniaturized, portable electronic devices, and electric vehicles. Among all the EES devices, supercapacitors with electrode materials derived from biosources have attracted special attention due to their eco‐friendliness, natural abundance, their intrinsic porous structures as well as their renewable and sustainable features. However, the relatively low packing densities make their specific volumetric capacitance intrinsically low, which has largely limited their further application in the supercapacitors. To address these issues, various promising approaches ranging from structural manufacture to compositional design are applied and significant breakthroughs are witnessed in recent years. In this progress report, key factors influencing the volumetric performance of biomass‐derived electrode materials are systematically discussed with a particular focus spanning from fundamental to operational aspects. This work provides insights into the development of high‐volumetric‐performance biomass‐derived supercapacitors by comprehensively summarizing recent advances in the rational structural design and fabrication. Perspectives regarding the future challenges and promising research directions on the design of next‐generation EES devices are also provided.     

Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities

In recent years, tremendous research effort has been aimed at increasing the energy density of supercapacitors without sacrificing high power capability so that they reach the levels achieved in batteries and at lowering fabrication costs. For this purpose, two important problems have to be solved: first, it is critical to develop ways to design high performance electrode materials for supercapacitors; second, it is necessary to achieve controllably assembled supercapacitor types (such as symmetric capacitors including double‐layer and pseudo‐capacitors, asymmetric capacitors, and Li‐ion capacitors). The explosive growth of research in this field makes this review timely. Recent progress in the research and development of high performance electrode materials and high‐energy supercapacitors is summarized. Several key issues for improving the energy densities of supercapacitors and some mutual relationships among various effecting parameters are reviewed, and challenges and perspectives in this exciting field are also discussed. This provides fundamental insight into supercapacitors and offers an important guideline for future design of advanced next‐generation supercapacitors for industrial and consumer applications.     

Recent advances in the separators for microbial fuel cells

Separator plays an important role in microbial fuel cells (MFCs). Despite of the rapid development of separators in recent years, there are remaining barriers such as proton transfer limitation and oxygen leakage, which increase the internal resistance and decrease the MFC performance, and thus limit the practical application of MFCs. In this review, various separator materials, including cation exchange membrane, anion exchange membrane, bipolar membrane, microfiltration membrane, ultrafiltration membranes, porous fabrics, glass fibers, J-Cloth and salt bridge, are systematically compared. In addition, recent progresses in separator configuration, especially the development of separator electrode assemblies, are summarized. The advances in separator materials and configurations have opened up new promises to overcome these limitations, but challenges remain for the practical application. Here, an outlook for future development and scaling-up of MFC separators is presented and some suggestions are highlighted.     

Recent Progress in Electrode Materials for Sodium‐Ion Batteries

Grid‐scale energy storage systems (ESSs) that can connect to sustainable energy resources have received great attention in an effort to satisfy ever‐growing energy demands. Although recent advances in Li‐ion battery (LIB) technology have increased the energy density to a level applicable to grid‐scale ESSs, the high cost of Li and transition metals have led to a search for lower‐cost battery system alternatives. Based on the abundance and accessibility of Na and its similar electrochemistry to the well‐established LIB technology, Na‐ion batteries (NIBs) have attracted significant attention as an ideal candidate for grid‐scale ESSs. Since research on NIB chemistry resurged in 2010, various positive and negative electrode materials have been synthesized and evaluated for NIBs. Nonetheless, studies on NIB chemistry are still in their infancy compared with LIB technology, and further improvements are required in terms of energy, power density, and electrochemical stability for commercialization. Most recent progress on electrode materials for NIBs, including the discovery of new electrode materials and their Na storage mechanisms, is briefly reviewed. In addition, efforts to enhance the electrochemical properties of NIB electrode materials as well as the challenges and perspectives involving these materials are discussed.     

Trans‐species synthetic gene design allows resistance pyramiding and broad‐spectrum engineering of virus resistance in plants

To infect plants, viruses rely heavily on their host's machinery. Plant genetic resistances based on host factor modifications can be found among existing natural variability and are widely used for some but not all crops. While biotechnology can supply for the lack of natural resistance alleles, new strategies need to be developed to increase resistance spectra and durability without impairing plant development. Here, we assess how the targeted allele modification of the Arabidopsis thaliana translation initiation factor eIF4E1 can lead to broad and efficient resistance to the major group of potyviruses. A synthetic Arabidopsis thaliana eIF4E1 allele was designed by introducing multiple amino acid changes associated with resistance to potyvirus in naturally occurring Pisum sativum alleles. This new allele encodes a functional protein while maintaining plant resistance to a potyvirus isolate that usually hijacks eIF4E1. Due to its biological functionality, this synthetic allele allows, at no developmental cost, the pyramiding of resistances to potyviruses that selectively use the two major translation initiation factors, eIF4E1 or its isoform eIFiso4E. Moreover, this combination extends the resistance spectrum to potyvirus isolates for which no efficient resistance has so far been found, including resistance‐breaking isolates and an unrelated virus belonging to the Luteoviridae family. This study is a proof‐of‐concept for the efficiency of gene engineering combined with knowledge of natural variation to generate trans‐species virus resistance at no developmental cost to the plant. This has implications for breeding of crops with broad‐spectrum and high durability resistance using recent genome editing techniques.     

Thick Electrode Batteries: Principles,Opportunities, and Challenges

The ever‐growing portable electronics and electric vehicle markets heavily influence the technological revolution of lithium batteries (LBs) toward higher energy densities for longer standby times or driving range. Thick electrode designs can substantially improve the electrode active material loading by minimizing the inactive component ratio at the device level, providing a great platform for enhancing the overall energy density of LBs. However, extensive efforts are still needed to address the challenges that accompany the increase in electrode thickness, not limited to sluggish charge kinetics and electrode mechanical instability. In this review, the principles and the recent developments in the fabrication of thick electrodes that focus on low‐tortuosity structural designs for rapid charge transport and integrated cell configuration for improved energy density, cell stability, and durability are summarized. Advanced thick electrode designs for application in emerging battery chemistries such as lithium metal electrodes, solid state electrolytes, and lithium–air batteries are also discussed with a perspective on their future opportunities and challenges. Finally, suggestions on the future directions of thick electrode battery development and research are suggested.     

Looking Ahead in Rice Disease Research and Management

Rice production is subject to increasing environmental and social constraints. Agricultural labor and water, which are key resources for rice production, illustrate this point. Nearly all rice-producing countries face reduced availability of agricultural water and shortage of farm labor. Plant pathologists should be concerned with such large-scale evolutions because these global drivers have an impact on not only the rice production system but also on the individual field and single-rice-plant levels. These concerns are closely associated with the long-term sustainability and environmental consequences of the intensification of agricultural systems brought about by problems of feeding a rapidly growing human population. Furthermore, genetic diversity in rice production has been reduced, thus inducing frequent disease epidemics and pest outbreaks. Looking ahead, we need to realize the need to maintain the diversity and yet retain the high productivity of the system. Natural resources, including genetic resources, are not infinitely abundant. We have to be efficient in utilizing genetic resources to develop durable resistance to rice diseases. Developing resistance is an important first step in tackling the disease problem, but it is not the only step available to achieve durability. Deployment of resistance must be considered in conjunction with development of host plant resistance. To attain durability, we need a better understanding of the coevolution process between the pathogen and the host resistance gene. Our target is an integrated gene management approach for better disease control and more effective utilization of genetic resources. Plant pathology, as an applied science, derives its strengths from various disciplines. To do the job right, we need a better understanding of the pathosystems, the epidemiology, and the coevolution process between the pathogen and the host resistance gene. The challenge, as pointed out by pioneers in our profession, is to prove the usefulness and the relevance of our research. Thus, we need to strike a balance between mission-oriented and fundamental research and make sure that our profession is (still) useful in the information technology and genomic era. We believe that a gene-based and a resource-based disease management approach should allow us to incorporate these new scientific developments. However, we do need to incorporate the new science for fundamental research to solve practical problems of rice production.     

Miniaturizing microbial fuel cells

Microbial fuel cells (MFCs) represent an emerging technology for electricity generation from renewable biomass. Given the demand for a better understanding of the bio/inorganic interface that plays a key role in MFC energy production, small-scale MFCs are receiving considerable attention owing to their intrinsic advantages in both fundamental studies and applications as high-throughput platforms. Here, we present a brief review centered on the development of miniature MFCs at the milliliter to microliter scale. The principles, design motifs and experimental demonstrations of representative miniature MFC devices and systems are introduced, followed by a discussion of the key challenges and opportunities for realizing the exciting potentials of miniaturized MFCs.     

Approaches to the discovery of new antibacterial agents based on bacteriocins.

The development of antibiotic resistance in pathogenic bacteria has led to a search for novel classes of antimicrobial drugs. Bacteriocins are peptides that are naturally produced by bacteria and have considerable potential to fulfill the need for more effective bacteriocidal agents. In this mini-review, we describe research aimed at generating analogues of bacteriocins from lactic acid bacteria, with the goal of gaining a better understanding of structure-activity relationships in these peptides. In particular, we report recent findings on synthetic analogues of leucocin A, pediocin PA1, and lacticin 3147 A2, as well as on the significance of these results for the design and production of new antibiotics.     

A Common View of the Opportunities, Challenges, and Research Actions for Pongamia in Australia

Interest in biofuels is increasing in Australia due to volatile and rising oil prices, the need to reduce GHG emissions, and the recent introduction of a price on carbon. The seeds of Pongamia (Millettia pinnata) contain oils rich in C18:1 fatty acid, making it useful for the manufacture of biodiesel and other liquid fuels. Preliminary assessments of growth and seed yield in Australia have been promising. However, there is a pressing need to synthesise practical experience and existing fragmented research and to use this to underpin a well-founded and co-ordinated research strategy to support industry development, including better management of the risks associated with investment. This comprehensive review identifies opportunities for Pongamia in Australia and provides a snapshot of what is already known and the risks, uncertainties, and challenges based on published research, expert knowledge, and industry experience. We conclude that whilst there are major gaps in fundamental understanding of the limitations to growth of Pongamia in Australia, there is sufficient evidence indicating the potential of Pongamia as a feedstock for production of biofuel to warrant investment into a structured research and development program over the next decade. We identify ten critical research elements and propose a comprehensive research approach that links molecular level genetic research, paddock scale agronomic studies, landscape scale investigations, and new production systems and value chains into a range of aspects of sustainability.     

Polymer Design Strategies for Radiation‐Grafted Fuel Cell Membranes

In the past decade, fuel cell technology has been moving steadily towards commercialization, with prospects of high production volumes, in particular in electric vehicle applications. However, the cost and durability of the currently‐used materials and components fall short of the requirements for large‐scale industrialization. The development of alternative, more cost‐effective materials with competitive performance and durability attributes is therefore ongoing. Radiation‐induced graft copolymerization (“radiation grafting”) is a versatile method to modify pre‐existing polymers to introduce a variety of desired functionalities, such as ion‐exchange capacity. Here, an overview of fundamentals and recent developments in the area of radiation grafted ion‐conducting polymers for application in polymer electrolyte fuel cells (PEFCs) is provided. Key aspects of polymer design are discussed, taking into consideration the radiation chemistry of base polymer materials and the adequate choice of grafting monomers for different PEFC types. Furthermore, the current status of applications in fuel cells is highlighted.     

Potential synergies and challenges in refining cellulosic biomass to fuels,chemicals, and power

Lignocellulosic biomass such as agricultural and forestry residues and dedicated crops provides a low-cost and uniquely sustainable resource for production of many organic fuels and chemicals that can reduce greenhouse gas emissions, enhance energy security, improve the economy, dispose of problematic solid wastes, and improve air quality. A technoeconomic analysis of biologically processing lignocellulosics to ethanol is adapted to project the cost of making sugar intermediates for producing a range of such products, and sugar costs are predicted to drop with plant size as a result of economies of scale that outweigh increased biomass transport costs for facilities processing less than about 10,000 dry tons per day. Criteria are then reviewed for identifying promising chemicals in addition to fuel ethanol to make from these low cost cellulosic sugars. It is found that the large market for ethanol makes it possible to achieve economies of scale that reduce sugar costs, and coproducing chemicals promises greater profit margins or lower production costs for a given return on investment. Additionally, power can be sold at low prices without a significant impact on the selling price of sugars. However, manufacture of multiple products introduces additional technical, marketing, risk, scale-up, and other challenges that must be considered in refining of lignocellulosics.     

Progress and Prospects in Symmetrical Solid Oxide Fuel Cells with Two Identical Electrodes

Symmetrical solid oxide fuel cells (SOFCs) have attracted increasing attention due to their potential for improved thermomechanical compatibility of the electrolyte and the electrodes, reduced fabrication cost, and enhanced immunity to coking and sulfur poisoning. While the electrode materials of symmetrical SOFCs are initially limited to those with stable phase structures under both reducing and oxidizing atmospheres, many novel electrode materials are currently being developed and investigated that may undergo a beneficial phase transition or reduction in a reducing atmosphere, although the same material may be used initially for the construction of both anode and cathode. Here, the advances made in the development of electrode materials and structures for symmetrical SOFCs are summarized, including single‐phase electrodes, multi‐phase (composite) electrodes, and those that are reducible upon exposure to a reducing atmosphere. The electrical conductivity, thermomechanical properties, and redox behavior of these electrode materials, together with their performance and stability in different SOFCs, are discussed and analyzed. The problems associated with different types of symmetrical SOFCs are outlined and the materials that show promise as symmetrical electrodes are highlighted, offering critical insights and useful guidelines for knowledge‐based rational design of better electrodes for commercially viable symmetrical SOFCs.     

利用木质纤维素生产丁醇的研究进展

随着化石燃料的逐年减少,以生物质为原料的生物能源研究近年来成为能源领域的研究热点,充分利用可再生生物质为发展经济的生物燃料生产工艺提供了一个极好的机会。与燃料乙醇和生物柴油相比,生物丁醇更具有优越性,以可再生木质纤维素生物质为原料进行发酵生产丁醇在近年来被广泛的研究。对于利用可再生生物质为原料生产丁醇,需要解决原料的选择、产品收率低、抑制物对生产菌株毒性等问题。本文对以木质纤维素生物质为原料进行生物丁醇发酵过程中的原料预处理、抑制物对丁醇生产菌的影响,以及水解液的脱毒和耐抑制物菌株的选育等方面进行综述,并对以木质纤维素生产燃料丁醇所面临的机遇与问题进行了简要评述。     

Efficient Oxygen Reduction Catalysts of Porous Carbon Nanostructures Decorated with Transition Metal Species

Developing substitutes of noble metal catalysts toward oxygen reduction reaction (ORR) at the cathode is of vital importance for promoting low‐temperature polymer electrolyte membrane fuel cells. Transition metal species have been one of the hot areas of interest due to their low cost, high activity, and long‐term stability. The design of porous carbon nanostructures decorated with transition metal species plays a vital role in enhancing ORR catalytic performance. Here, the recent breakthroughs in porous carbon nanostructures decorated with transition metal species (including nanoparticles and atomically dispersed supported metal) are discussed. The porous nanostructures can provide large surface area as well as abundant pore channels, leading to sufficient exposure of active sites and efficient mass transfer. These nanostructures can be synthesized by several approaches, including the templated method, the self‐templated method, the impregnation process, and so on. Furthermore, the ORR performance and the exploration of active sites are also discussed for further enhancement of the ORR catalysts. Finally, the challenges and prospects are discussed, which would push forward the development of ORR catalysts in the near future.