National Nanotechnology Infrastructure Network Research Articles

Accessible Surface Area in Porous Carbon Electrodes and Its Impact on Redox Flow Battery Performance

Carbon-fiber electrodes exhibit many desirable material properties including conductivity, porosity, and chemical stability, and, accordingly, are employed in a range of electrochemical technologies.1 Such electrodes are particularly important in redox flow battery (RFB) systems, as they serve multiple critical functions including providing surface area for electrochemical reactions, distributing liquid electrolytes, and conducting electrons and heat. While commercially available materials possess suitable permeability and conductivity, the performance of pristine substrates is limited, thus oxidative treatment prior to use is common practice.2,3 Partial oxidation of the electrode surface has been shown to add a range of oxygen functional groups, which improve hydrophilicity and, in some cases, catalyze redox reactions, as well as to increase available surface area for the electrochemical reactions.4,5 Both effects are posited to improve electrode performance but their relative importance and effectiveness remains unclear.6 Here, we critically assess the nature of the surface area generated by thermal pretreatment in air and its role on RFB electrode performance. Using binder-free Freundenberg H23 as a model substrate, we systematically vary pretreatment time and temperature to create different surface morphologies and develop structure-function relations. First, we use Brauner Emmanuel Teller gas adsorption (e.g., N2, Kr, Ar/CO2) and mercury porosimetry to estimate physical surface area and pore size distribution. In parallel, we use voltammetry and impedance spectroscopy to determine electrochemically active surface area with different electrolyte compositions. In general, we find that only a fraction of the physical surface area is accessible for electrochemical redox reactions due, in large part, to the nanoscopic dimensions of the added surface area. Second, we develop a simple mathematical model to assess the effectiveness of the available surface area of carbon fibers for Faradaic reactions. We find that, under typical RFB operating conditions, external mass transfer limitations govern performance, limiting the utilization of recessed areas generated during pretreatment. Ultimately, these results highlight the potential limits of performance improvement strategies based on increasing surface area of fibrous substrates and motivate new approaches for electrode development. Acknowledgements The authors acknowledge the financial support of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the United States Department of Energy. K.V.G acknowledges additional funding from the National Science Foundation Graduate Research Fellowship. The authors acknowledge the Center for Nanoscale Systems and the NSF’s National Nanotechnology Infrastructure Network (NNIN) for the use of Nanoscale Analysis facility for electrode property characterization. References M. H. Chakrabarti et al., Journal of Power Sources, 253, 150–166 (2014).T. J. Rabbow, M. Trampert, P. Pokorny, P. Binder, and A. H. Whitehead, Electrochimica Acta, 173, 17–23 (2015).N. Pour et al., The Journal of Physical Chemistry C, 119, 5311–5318 (2015).B. Sun and M. Skyllas-Kazacos, Electrochim. Acta, 37, 8 (1992).T. J. Rabbow and A. H. Whitehead, Carbon, 111, 782–788 (2017).K. V. Greco, A. Forner-Cuenca, A. Mularczyk, J. Eller, and F. R. Brushett, ACS Applied Materials & Interfaces, 10, 44430–44442 (2018).

Deconvoluting the Effects of Surface Area, Functionalization, and Wetting on the Performance of Porous Carbon Electrodes in Aqueous Redox Flow Batteries

Redox flow batteries (RFBs) are a promising electrochemical technology for grid-scale energy storage, but further cost reductions are needed for ubiquitous adoption.1 Of particular importance are porous electrodes which are responsible for multiple critical functions in the flow cell including providing surfaces for electrochemical reactions, distributing liquid electrolytes, and conducting electrons and heat. However, there is limited knowledge on how to systematically design and implement these materials in emerging RFB applications, forcing the repurposing of available materials that are not tailored for this electrochemical system. Currently, high performance RFB reactors employ porous electrodes based on the fibrous carbon backing layers of fuel cell gas diffusion layers. While functional, these materials are not designed to meet all RFB requirements and are typically pretreated prior to use.2,3 Arguably the most widely-reported pretreatment strategy, thermal oxidation in air provides a means of introducing redox-enhancing oxygen functional groups to the electrode surface and improving hydrophilicity, albeit often at the expense of electrochemically active surface area (ECSA).4,5 Consequently, optimal performance is achieved by a balance of electrode properties rather than a maximization of each. Unfortunately, the potential- and temperature-dependence of underlying structure-property relationships remain poorly understood and, thus, electrode optimizations are typically performed via trial-and-error approaches. In this presentation, we will investigate the interplay between surface functionalization, wetting, and surface area on the performance of porous carbon electrodes in aqueous RFBs. Specifically, we systematically vary pretreatment conditions (e.g., temperature, time, atmosphere) for select porous carbon electrodes, characterize their wettability, surface chemistry, and ECSA, and correlate these properties to electrochemical performance. To this end, we leverage model surface-sensitivity redox couples over a range of potentials in combination with diagnostic flow cell configurations to disaggregate coupled effects and identify dominant sensitivities. Overall, we seek to determine generalizable performance descriptors that can guide the design of next-generation electrodes specifically for RFB applications. Acknowledgements The authors acknowledge the financial support of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the United States Department of Energy. K.V.G acknowledges additional funding from the National Science Foundation Graduate Research Fellowship. The authors acknowledge the Center for Nanoscale Systems and the NSF’s National Nanotechnology Infrastructure Network (NNIN) for the use of Nanoscale Analysis facility for electrode property characterization. References M. Skyllas-Kazacos, M. H. Chakrabarti, S. A. Hajimolana, F. S. Mjalli, and M. Saleem, J. Electrochem. Soc., 158, R55 (2011).T. J. Rabbow, M. Trampert, P. Pokorny, P. Binder, and A. H. Whitehead, Electrochimica Acta, 173, 17–23 (2015).N. Pour et al., J. Phys. Chem. C, 119, 5311–5318 (2015).B. Sun and M. Skyllas-Kazacos, Electrochimica Acta, 37, 8. (1992).K. V. Greco, A. Forner-Cuenca, A. Mularczyk, J. Eller, and F. R. Brushett, ACS Appl. Mater. Interfaces, 10, 44430–44442 (2018).

Development and Pilot Testing of an Evidence-Based Training Module for Integrating Social and Ethical Implications into the Lab

In this project, we (1) explore perceptions of the social and ethical implications (SEI) of nanotechnology among US scientists who work at the nanoscale, and (2) develop and pilot test an online training module to foster consideration of social and ethical implications in the lab. To meet our first goal, we drew qualitative insights from open-ended survey data collected from scientists affiliated with the National Nanotechnology Infrastructure Network. Our data suggest that while the survey participants responded positively to the idea that consideration of SEI should be a part of the work they do, there was confusion about whether SEI refers to lab safety, research integrity, or something more. This is something we sought to address in the online training module that we developed based on that qualitative data and on feedback collected from experts in nanoethics and lab management. We then pilot tested the module with undergraduate students studying nanotechnology in the National Science Foundation’s Research Experiences for Undergraduates (REU) program and with scientists registered to use a National Nanotechnology Coordinated Infrastructure-funded microelectronics research lab. The undergraduate data suggested that students appreciated the SEI training but wished professors and scientists would begin integrating the ideas therein into coursework and mentoring. The scientist data suggested that the module increased understanding of “social and ethical implications,” increased the perceived need to implement SEI into workplace routines, and, interestingly, heightened perceptions of risk associated with the scientists’ own work. The practical and theoretical implications of this work are discussed.

Exploring the Influence of Thermal Pretreatment on Carbon Paper Electrodes for Vanadium Redox Flow Batteries

Grid-scale energy storage is anticipated to play a critical role in the decarbonization of the electric power sector by enabling the reliable integration of intermittent renewable sources and increasing the efficiency of non-renewable energy processes.1 Redox flow batteries (RFBs) are a promising electrochemical device for such applications due to their independent energy and power scaling and long operational lifetime.2 Aqueous vanadium RFBs (VRBs) have been the most successful chemistry, due to their high power density and recoverable capacity from crossover, but further cost reductions are needed for ubiquitous adoption. Vanadium redox reactions have sluggish kinetics on the carbon electrodes typically employed in VRBs which motivates the implementation of pretreatment strategies to increase electrochemically active surface area and introduce catalytically active functional groups onto the electrode surface.3 While many pretreatments have been successfully demonstrated most studies are empirically-driven.4 Few have focused on systematically correlating changes in electrode structure and surface chemistry to shifts in electrochemical performance. To this end, we utilize a suite of ex-situ characterization techniques, coupled with flow cell testing, to explore structure-performance relations of thermally pretreated carbon paper electrodes. Specifically, we vary thermal pretreatment temperature from 400 °C, a commonly used temperature for VRB electrode treatments3,4, to 500 °C, to quantify changes in the physicochemical properties of the electrode, and link these changes to shifts in VRB performance. We leverage microscopic, spectroscopic, and analytical techniques to determine how microstructural, morphological, and chemical properties of electrodes are impacted by thermal pretreatment. We then evaluate the effect of these properties on flow cell performance using polarization, electrochemical impedance spectroscopy, and cell cycling. We find that many factors contribute to the observed electrode performance, including hydrophilicity, electrochemical surface area, and surface chemistry, and that not all of these factors improve with increasing temperature. Consequently, while the best overall performance is achieved with pretreatment at 475 °C, a 26% increase in maximum power density over the base case of pretreatment at 400 °C, this enhancement is based on a balance of critical properties rather than a maximization of all. Acknowledgements The authors acknowledge the financial support of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the United States Department of Energy. K.V.G acknowledges additional funding from the National Science Foundation Graduate Research Fellowship. A.F.C. acknowledges financial support from the Swiss National Science Foundation (P2EZP2_172183). The authors acknowledge the Center for Nanoscale Systems and the NSF’s National Nanotechnology Infrastructure Network (NNIN) for the use of Nanoscale Analysis facility to collect X-ray photoelectron spectroscopy data. We thank Michael L. Perry and Robert M. Darling for guidance in experimental conditions and critical evaluation of results. References Z. Yang, J. Zhang, M. Kintner-Meyer, X. Lu, D. Choi, J. P. Lemmon, J. Liu, Chem. Rev., 111, 3577–3613 (2011).M. Skyllas-Kazacos, M. H. Chakrabarti, S. A. Hajimolana, F. S. Mjalli, and M. Saleem, J. Electrochem. Soc., 158, R55 (2011).B. Sun and M. Skyllas-Kazacos, Electrochim. Acta, 37, 1253–1260 (1992).M. H. Chakrabarti et al., J. Power Sources, 253, 150–166 (2014). Figure 1

Aware, Yet Ignorant: Exploring the Views of Early Career Researchers About Funding and Conflicts of Interests in Science.

This study investigates the level of awareness about funding influences and potential conflicts of interests (COI) among early career researchers. The sample for this study included users of one or more of the 14 U.S. laboratories associated with the National Nanotechnology Infrastructure Network. To be eligible, respondents must have been either still completing graduate work or <5years since graduation. In total, 713 early career researchers completed the web survey, with about half still in graduate school. Results indicate that although respondents were aware of potential funding and COI influences on their work, they remained largely ignorant of their role in addressing or managing these issues. Respondents often attributed the responsibility of addressing these issues to their supervisors. Respondents who had received some training around these issues, however, were more likely to assume more personal responsibility. Overall, this study points out that ignorance among early career researchers is less about awareness of funding and COI issues and more about taking personal responsibility for addressing these issues.

Caring for nanotechnology? Being an integrated social scientist.

One of the most significant shifts in science policy of the past three decades is a concern with extending scientific practice to include a role for 'society'. Recently, this has led to legislative calls for the integration of the social sciences and humanities in publicly funded research and development initiatives. In nanotechnology--integration's primary field site--this policy has institutionalized the practice of hiring social scientists in technical facilities. Increasingly mainstream, the workings and results of this integration mechanism remain understudied. In this article, I build upon my three-year experience as the in-house social scientist at the Cornell NanoScale Facility and the United States' National Nanotechnology Infrastructure Network to engage empirically and conceptually with this mode of governance in nanotechnology. From the vantage point of the integrated social scientist, I argue that in its current enactment, integration emerges as a particular kind of care work, with social scientists being fashioned as the main caretakers. Examining integration as a type of care practice and as a 'matter of care' allows me to highlight the often invisible, existential, epistemic, and affective costs of care as governance. Illuminating a framework where social scientists are called upon to observe but not disturb, to reify boundaries rather than blur them, this article serves as a word of caution against integration as a novel mode of governance that seemingly privileges situatedness, care, and entanglement, moving us toward an analytically skeptical (but not dismissive) perspective on integration.

An analysis of nanoscientists as public communicators

The American public remains unfamiliar with nanotechnology despite more than a decade of investment and development. Nanoscientists have an opportunity to contribute to public conversations about their work, and its potential implications, through their engagement with lay audiences and media professionals. Indeed, the leaderships of many professional scientific organizations have placed a renewed focus on the public communication of science, particularly in the light of drastic changes in the information landscape and the increasing politicization of many technological and scientific issues. However, we have a limited understanding of nanoscientists' perceptions and behaviours regarding their participation in public communication. Here, we report survey results that provide an examination of the public communication behaviours of nanoscientists affiliated with the National Science Foundation's (NSF) National Nanotechnology Infrastructure Network (NNIN), an integrated partnership of US research institutions designed to facilitate nanoscale research and development. Our results suggest that nanoscientists are relatively frequent public communicators who commonly associate their communication efforts with positive impacts on their professional success. We also identify a handful of characteristics that drive nanoscientists' intentions to communicate with the public about nanotechnology.

Exploring Societal and Ethical Views of Nanotechnology REUs

Little previous research has examined attitudes about societal and ethical issues (SEI) among interns participating in research experience for undergraduate programs (REUs) in nanotechnology, thus neglecting an important population for understanding the burgeoning views of the next generation of nanotechnology researchers. This study surveyed a sample of interns (N = 85) participating in the National Nanotechnology Infrastructure Network’s (NNIN) REU program during the summer of 2012. Our questions focused on interns’ experiences with education on ethical issues, as well as their attribution of responsibility for considering ethical issues, motivations to talk about ethical issues, and comfort level of discussing ethical issues with faculty, mentors, lab staff, and other REU students. Among key findings was that lab culture related to the extent to which REU interns felt comfortable discussing ethical issues. In addition, those who reported more discussions about ethical issues with their mentors were more likely to consider themselves as responsible for considering ethical issues. We conclude with recommendations and future research directions.

Managing Nanotechnology Risks in Vulnerable Populations: A Case for Gender Diversity

AbstractFunded by the National Science Foundation and the National Nanotechnology Infrastructure Network (NNIN), this study asks qualitatively analyzes interviews with 48 nanoscientist users at four NNIN facilities. The main research questions were: (1) Do nanotechnologies pose unique social and ethical concerns?; (2) how are the risks associated with nanotechnology distributed among different human populations?; (3) what are specific policy steps that can be used to manage such risks? This study purposefully oversampled female scientists to correct for the historical underrepresentation of women in the nanotechnology workforce. By amplifying the voice of this science, technology, engineering, and mathematics (STEM) workforce minority, the policy discussion contained herein better reflects the concerns of the general population. The results, analyzed with the aid of qualitative data analysis software, yield interesting differences in risk characterization among the scientists and innovative policy suggestions for the nanoscience community and regulators alike.

The National Nanotechnology Infrastructure Network's Education and Outreach Programs - Helping student understand the tools of nanotechnology

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

From Materials Science to Nanotechnology: Interdisciplinary Center Programs at Cornell University, 1960–2000

During the last several decades, interdisciplinary research centers have emerged as a standard, powerful tool for federal funding of university research. This paper contends that this organizational model can be traced to the “Interdisciplinary Laboratories” program funded by the Advanced Research Projects Agency in 1960. The novelty of the IDL program was that it created a peer group of university laboratories with sustained funding to ensure their institutional stability. The Cornell Materials Science Center, one of the first three Interdisciplinary Laboratories, served as a breeding ground for a new community of engineering faculty members, who subsequently helped establish a series of interdisciplinary research centers at Cornell, including the National Research and Resource Facility for Submicron Structures (or National Submicron Facility) in 1977. The Materials Science Center and National Submicron Facility provided explicit models for the expansion and coordination of networks of interdisciplinary centers, both within single universities (such as Cornell) and across multiple campuses (through programs such as the National Nanotechnology Infrastructure Network and the Nanoscale Science and Engineering Centers). The center model has proved both flexible and durable in the face of changing demands on universities. By examining the Materials Science Center and the National Submicron Facility, we show that recent institutional developments perceived as entirely novel have their roots in the high Cold War years.

Responsible Development of Nanoscience and Nanotechnology: Contextualizing Socio-Technical Integration into the Nanofabrication Laboratories in the USA

There have been several conscious efforts made by different stakeholders in the area of nanoscience and nanotechnology to increase the awareness of social and ethical issues (SEI) among its practitioners. But so far, little has been done at the laboratory level to integrate a SEI component into the laboratory orientation schedule of practitioners. Since the laboratory serves as the locus of activities of the scientific community, it is important to introduce SEI there to stimulate thinking and discussion of SEI among practitioners, which would eventually contribute toward the responsible development of this technology. In this article, through an example (at the Cornell NanoScale Science and Technology Facility (CNF), practitioners of which represent a section of the nano researchers’ community in the USA), it is shown how a SEI component can be incorporated into the laboratory orientation schedule of the practitioners from diverse disciplinary and institutional backgrounds. Results show that, at CNF, the practitioners enjoyed the discussion since most of them learned about SEI for the first time in their professional career. At the same time, some of them were also knowledgeable about SEI and contributed to the debates. Moreover, the SEI orientation had significant positive impact on the scientific community enabling them to self-reflect upon their own research and its implications for the wider society. This article also describes the efforts that were undertaken to disseminate this form of SEI orientation to other 13 USA universities within the National Nanotechnology Infrastructure Network (NNIN, one of the biggest networks funded from National Science Foundation for Nanotechnology research, of which CNF is a part). As a result of this effort, most of the NNIN sites have already started or were in the process of integrating a SEI component into their nanofabrication laboratories to make their users aware of SEI, ensuring eventual robust socio-technical integration in the NNIN laboratories. In the future, this form of SEI orientation can also be disseminated to other nanofabrication laboratories in the USA.

Optical 4x4 hitless Silicon router for optical Networks-on-Chip (NoC): erratum

An erratum is presented to add the proper acknowledgements for this work. ©2008 Society of America OCIS codes: (060.4250) Fiber optics and optical communications: Networks; (130.4815) Integrated optics: switching devices; (230.3990) devices: Micro-optical devices. References and links 1. N. Sherwood-Droz, H. Wang, L. Chen, B. G. Lee, A. Biberman, K. Bergman, and M. Lipson, Optical 4x4 hitless slicon router for optical networks-on-chip (NoC), Opt. Express 16, 15915-15922 (2008). Acknowledgments This work was performed in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation. This work is also partly funded by the Center for Nanoscale Systems, supported by the NSF and the New York State Office of Science, Technology and Academic Research. The authors also thank the Interconnect Focus Center Research Program (IFC) which is supported in part by the Microelectronics Advanced ResearchCorporation (MARCO), and its participating companies, for the partial support of this work. [1] (C) 2008 OSA 10 November 2008 / Vol. 16, No. 23 / OPTICS EXPRESS 19395 #103706 $15.00 USD Received 5 Nov 2008; published 7 Nov 2008

Potential risks of nanomaterials and how to safely handle materials of uncertain toxicity

In the last few years, the number of research studies on the toxicity of different types of nanomaterials has increased dramatically. These studies have suggested effects at the cellular level and in short-term animal tests. The effects seen depend on the base material of the nanoparticle, its size and structure, and its substituents and coatings. Additional toxicology testing is being funded or planned by the National Nanotechnology Infrastructure Network and other research organizations in the US and in Europe. Nanomaterials of uncertain toxicity can be handled using the same precautions currently used at universities to handle other materials of unknown toxicity: use of exhaust ventilation (such as fume hoods and vented enclosures) to prevent inhalation exposure during procedures that may release aerosols or fibers and use of gloves to prevent dermal exposure. This article presents an overview of some of the major questions in nanotoxicology and also discusses the best practices that universities such as MIT and others are currently using to prevent exposure.

The highlights in the nano world

In this highlight paper, the key structures and devices in nanoelectronics and spintronics are described. The successful realization of magnetic RAM (MRAM) by using nanotechnology has been demonstrated through the integration of 1-Mb chip. In this design, the pseudo spin valve (PSV) technology has been applied. Key quantum devices like quantum dot surface emitting lasers, quantum dot intersubband detectors, and molecular electronics are presented. In the emergent nanobiotechnology, nanodevices fabricated by using biotechnology and nanobiomedical applications using nanoparticles have been addressed. Since universities play important roles in both research and education, innovative nanotechnology education efforts in universities such as the National Nanotechnology Infrastructure Network have been described. Finally, the leading role of the IEEE in promoting worldwide nanotechnology research and education is addressed and future advances in nanotechnology are expected.