Nanomaterials for Energy Conversion and Storage

Guest Editors Jang Wook Choi, Donghai Wang, and Dunwei Wang introduce the topics covered in this special issue on nanomaterials for energy conversion and storage. We are living in a unique time, the Anthropocene. Never has this lonely planet seen a single species dominate the biosphere the way we do now. Humans directly impact over 60% of the land surface and 41% of marine environments. We consume 40% of the plants grown in a given year. Most significant of all, we are digging out and burning fossil fuels at an alarmingly fast pace, emitting 36 gigatons of CO2 and 160 tons of SO2 a year, which alters global weather patterns for the worse. The mounting evidence compels us to take actions to curb and, ultimately, to reverse this current trend. A critical step toward this goal is to free ourselves from our reliance on fossil fuels by switching to renewable energy sources. Technologies that can enable us to better adapt to a new, renewables-based energy infrastructure would need to take the front seat in such a pursuit. Within this framework, we present this special issue to report the latest research on energy conversion and storage by leading experts around the globe. There are at least two important reasons for the development of energy conversion and storage technologies. First, highly efficient and inexpensive energy conversion and storage is key to addressing the issues connected to the intermittent nature of renewable energy sources, be it wind, tidal or solar. For more convenient, sustainable adoption in our everyday life, renewable energy sources should be converted to different energy forms, such as chemical energy in batteries that can be extracted as electricity whenever needed. Second, an on-demand energy supply is central to meeting societal needs, which are increasingly mobile. In response to such needs, a diverse range of chemistries have been studied and are included here, such as capacitors and supercapacitors (see Zhang, Yan et al., Wei, Zhou et al., Lu et al., Xia, Xie et al., and Yao et al.), Li-ion batteries (see Cao et al. and Zhu et al.), Na-ion batteries (see Yu et al.), Li-S batteries (see Cong, Yu et al. and Kaskel et al.), and Li-O2 batteries (see Lu, Ji et al.). There is also a need for direct solar-to-chemical energy conversion, such as solar water splitting (see Shen et al., Valenti, Schmidt-Ott, Smith et al., Maeda et al. and Yang et al.). In addition, Wang et al. report a new synthesis of metal dichalcogenides, an emerging class of materials with intriguing properties in the area of catalysis and photocatalysis. Photocatalysis by an organic/inorganic hybrid system is also discussed in Li et al.’s report. As is true in many other fields, the development of energy conversion and storage technologies hinges on the availability of suitable materials. The dependence may be particularly strong for the topics discussed here as the issues that limit the performance of energy conversion and storage devices are by and large materials-related ones. The emergence of new materials, such as 2D materials (see review by Yan et al.), always inspires new ideas and applications. Parameters which define the desired materials for energy conversion and storage are diverse, but they often share a conspicuous commonality: the characteristic length scale of charge behaviors. This length scale is the nanoscale. As such, great efforts have been devoted to synthesizing, characterizing and utilizing nanomaterials. It is safe to guess that controls over materials’ features at the nanoscale will be pivotal to any inroads toward a future powered by renewable energy sources. It is our sincere hope that reports compiled in this special issue will serve as catalysts for broader discussion of energy conversion and storage. Jang Wook Choi is currently an Associate Professor in the Graduate School of Energy, Environment, Water, and Sustainability (EEWS) at Korea Advanced Institute of Science and Technology (KAIST) in the Republic of Korea. Prof. Choi received a B.S. from the Department of Chemical Engineering at Seoul National University in 2002 and a Ph.D. from the Division of Chemistry and Chemical Engineering at Caltech in 2007 under the supervision of Prof. James R. Heath. Since then, Prof. Choi carried out Postdoctoral research in the Department of Materials Science and Engineering at Stanford University under the supervision of Prof. Yi Cui. He was appointed as an Assistant Professor at KAIST in 2010. His research interest lies in materials design and system development targeting rechargeable batteries, supercapacitors, and CO2 capture. Dr. Donghai Wang is currently an Associate Professor at the Department of Mechanical Engineering and Department of Chemical Engineering at The Pennsylvania State University. Before joining Penn State in 2009, he was a postdoc and subsequently became a staff scientist at Pacific Northwest National Laboratories where he developed functional materials for catalysis and energy storage techniques. He received a B.S. and Ph.D. degree in Chemical Engineering from Tsinghua University and Tulane University in 1997 and 2006, respectively. Dr. Donghai Wang's research interests have been related to the design and synthesis of materials for a variety of applications. His recent research efforts focus on material development for energy conversion and storage technologies such as batteries, fuel cells and solar fuels. Dunwei Wang graduated from the University of Science and Technology of China in 2000 with a B.S. in Chemistry. He then continued his study at Stanford University under the guidance of Prof. Hongjie Dai, graduating in 2005 with a Ph.D. in Chemistry. After two years of postdoctoral research with Prof. James R. Heath at California Institute of Technology, he joined Boston College as an Assistant Professor in 2007 and was promoted to Associate Professor with tenure in 2012. His research centers on solar energy conversion and storage. He is a recipient of the Prize for Young Chemist by IUPAC (2006), an NSF CAREER Award (2011), a CATALYSIS award from Massachusetts Clean Energy Center (2011), a Sloan Fellowship (2012), and a Japan Society for the Promotion of Science Fellowship (2016).