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ACS Editor’s Choice 2018: Significant Advances in Energy Research ver the course of 2018, ACS Energy Letters received and published many outstanding articles communicating the most urgent and interesting developments in fundamental and applied energy research of the year, with the aim of appealing to specialist and generalist audiences alike. While we stand behind the work of our authors and reviewers in ensuring the novelty and high quality of all articles published, a short-list have been recognized by our Editors and ACS as being particularly notable in their significance. These articles have been recognized as ACS Editors’ Choice and made available free of charge to all readers. The ACS Editors’ Choice articles comprise Letters, Perspectives, and a Review and describe the latest developments in topics including materials science and heterogeneous catalysis as they apply to improving the collection, generation, and/or storage of energy. We hope that you will take a look at these articles if you have not already done so, and stay tuned for more notable developments to be published in 2019! The operation of a device, whether it be for energy capture, generation, or storage, is dependent upon the design and production of materials that can efficiently support this function. As such, ACS Energy Letters authors have made important advancements in materials science for energy applications. In their Letter, Wu et al. (DOI: 10.1021/ acsenergylett.8b01025) address a major challenge in the production of three primary color displays through pursuing the development of higher photoluminescence quantum yields (QYs) for blue-emitting perovskite nanocrystals. While redand green-emitting nanocrystals have been reported to achieve near 100% QY, blue-emitting materials typically exhibit lower QY due to the propensity of these materials to form surface defects that result in nonradiative recombination. The authors develop an in situ passivation strategy by adding additional Br ions to drive the ionic equilibrium and thereby reduce Br vacancies in the Pb−Br octahedra during production of CsPbBr3 nanoplatelets (Figure 1). In situ passivation techniques are challenging to design but more convenient to undertake than complex post-treatment strategies used to reduce lattice defects. A 96% QY with 12 nm line width blue emission was achieved using the CsPbBr3 nanoplatelets generated in this manner, and the materials were subsequently used in the fabrication of blue light-emitting diodes that demonstrated a high external quantum efficiency of 0.124%. Christians et al. (DOI: 10.1021/acsenergylett.8b00914) set out an action plan for overcoming the practical challenge of durability in order to make halide perovskite photovoltaicbased solar cell technologies commercially viable in their ACS Energy Letters Perspective. In order to advance the status of degradation science, they view stability as a three-part system of materials, cell, and module; each component requires a distinct strategy to address its challenges. Stability is the final major hurdle to be addressed in widespread application as
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Figure 1. Wu et al. develop an in situ passivation method for the production of high quantum yield blue-emitting CsPbBr3 nanoplatelets with application to the production of light-emitting diodes. Reprinted from ACS Energy Lett., 2018, 3(9), pp 2030− 2037. Copyright 2018 American Chemical Society.
major milestones in performance consistency and device scalability are being met. The authors propose increased standardization throughout the research community in the definition of stability for perovskite photovoltaics and in the goals, methodology, and best practices used to evaluate materials and device structural stability. In order to obtain high performance in thermoelectric materials, low lattice thermal conductivity must be achieved. In their ACS Energy Letters Perspective, Jana and Biswas (DOI: 10.1021/acsenergylett.8b00435) explore the current status of the field in production of materials with low lattice thermal conductivity. The benefits to intrinsic versus extrinsic approaches for tailoring lattice thermal conductivity are discussed, and concepts important to the design of new thermoelectric materials (including lattice anharmonicity, lonepair effect, resonant bonding, intrinsic rattling, part-liquid states, and order−disorder transitions) are described. The authors identify that understanding the mechanisms of how low thermal conductivity can be achieved is key to future directions and the rational design of solid-state materials such that phonon transport can be engineered to direct the development of novel intrinsically low thermoconductive materials. Furthermore, they identify the future challenge of balancing the inherent susceptibility of low thermoelectric materials to structural degradation with the need for favorable device performance in order to bring promise for commercial application. Singlet exciton fission (SEF)-active materials bring promise for overcoming the Shockley−Queisser fundamental maximum Received: December 12, 2018 Accepted: December 17, 2018
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DOI: 10.1021/acsenergylett.8b02432 ACS Energy Lett. 2019, 4, 325−327
Energy Focus
Cite This: ACS Energy Lett. 2019, 4, 325−327
Energy Focus
ACS Energy Letters
Figure 2. Krishnapriya et al. sought to develop design principles for novel, efficient intramolecular singlet exciton fission-capable molecules. This is an important advancement in the production of solar cells that overcome the Shockley−Queisser limit of efficiency. Reprinted from ACS Energy Lett., 2019, 4(1), pp 192−202. Copyright 2019 American Chemical Society.
Figure 3. Roy et al. review the current status and future challenges of technologies for capture and thermochemical conversion of CO2 into single carbon products. Reprinted from ACS Energy Lett., 2018, 3(8), pp 1938−1966. Copyright 2018 American Chemical Society.
design principles for new molecules capable of efficient intramolecular SEF (Figure 2). The authors evaluated several series of multichromophoric and polymeric SEF materials from which they extracted proposed strategies for molecular design. The elucidation of complex catalytic mechanisms, catalyst design, and novel application of catalysts to address challenges in energy generation and storage has been a very active area of recent research. Impactful advancements to the field have been reported in ACS Energy Letters in 2018 and selected as ACS Editors’ Choice. In their Review, Roy et al. (DOI: 10.1021/ acsenergylett.8b00740) cover the current status and future
theoretical efficiency limit for solar cells and thereby bring promise for improving the efficiency of light-harvesting devices. Their rational design of SEF-active materials is limited by the fact that the current understanding of their properties is determined on the basis of thermodynamics methods which do not easily translate to rational molecular design. In order to address this challenge, Krishnapriya et al. (DOI: 10.1021/ acsenergylett.8b01833) adopted an interesting approach in their ACS Energy Letters Perspective whereby they compiled successful reports of the production of SEF-active materials and sought to identify commonalities that could serve as 326
DOI: 10.1021/acsenergylett.8b02432 ACS Energy Lett. 2019, 4, 325−327
Energy Focus
ACS Energy Letters outlook of thermochemical carbon capture and conversion, as well as the practical challenges currently faced in the development of these technologies (Figure 3). Thermochemical hydrogenation of CO2 into useful products offers a potentially commercially viable approach to reduce carbonbased emissions while generating industrially useful single carbon products such as those with potential for use as fuel substituents. The authors provide mechanistic insight into catalytic materials design while seeking out efficient, selective single carbon product catalysts. While this technology is not yet sufficiently mature for commercial viability, the authors point out that innovation in all facets of the approach ranging from CO2 hydrogenation technologies, design of the catalysts and reactors, methodology used for carbon capture, and finally to the development of renewable energy to power the thermochemical hydrogenation of CO2 are required in order for the technology to advance to widespread industrial adoption. Catalytic conversion of nitrogen to ammonia is a highly technically challenging process, and two 2018 ACS Editors’ Choice selections from ACS Energy Letters have sought to address the need for new approaches. In their Letter, Suryanto et al. (DOI: 10.1021/acsenergylett.8b00487) address the need for the development of a process for direct conversion of dinitrogen to ammonia that uses electricity from renewable sources; a goal that is noted as being of critical significance to policy makers and industry. If the production of NH3 can be accomplished in an efficient manner, NH3 is considered to be an ideal energy storage alternative for renewable energy. The efficiency of this catalytic ammonia production tends to be low (
