bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Analysis of Relative Graphene Layer Orientations Around FeN2+2 Sites for ORR
Authors: Gallenkamp Charlotte , Ni Lingmei , Krewald Vera , Kramm Ulrike Ingrid
Published: February 2020

Proton exchange fuel cells (PEFCs) are a promising technology for energy conversion, but are not yet commercialized due to highly expensive platinum as state-of-the-art catalyst for the cathodic oxygen reduction reaction (ORR). As low-cost materials with earth abundant metals, non-precious metal and nitrogen doped carbon catalysts (Me-N-C) have become a viable alternative for platinum. Encouraging results were especially achieved with the use of iron as the metal center.[1]

Me-N-C catalysts are obtained from pyrolysis of different metal, nitrogen and carbon precursors, which results in highly amorphous structures. The latter causes difficulties for the spectroscopic characterization of the active sites. Thus the exact chemical nature of the active center and the oxygen reduction reaction (ORR) mechanism are still being debated. [2]

So far, three sites were proposed as possible contributors to the ORR activity. In Mössbauer spectroscopy they give rise to the D1, D2 and D3 doublets. They are all assigned to some type of FeN4 centers that are either integrated in graphene layers (D1: FeN4) or situated between two graphene layers (D2 and D3: FeN2+2). [3] While in the case of the D1 doublet, FeN4 macrocycles seem to work well as a model system, in the case of the FeN2+2 sites it is difficult to find suitable molecular model systems as references for the interpretation of the Mössbauer data. Furthermore, in the literature this site is often displayed as a flat structure. However, it remains unclear to what extent the graphene layers could possibly be tilted against each other.

In this contribution, we will use density functional theory calculations to determine structure-property relationships of FeN2+2 site models with different Fe coordination environments – in particular the angle between adjacent graphene layers – with respect to relative energy, preferred spin state, Mössbauer spectroscopic parameters, and likely reaction intermediates for ORR.

[1] Szakacs, C.E. et al., Phys. Chem. Chem. Phys., 2014, 16, 13654.

[2] Kramm, U.I. et al., Adv. Mater., 2019, 1805623.

[3] Kramm, U.I. et al., Phys. Chem. Chem. Phys., 2012, 14, 11673–11688.
Highly Active Pd-CeO2-NR/C (cerium oxide nanorods) Bifunctional Nanocatalysts with Remarkable Stability for the Ethanol Oxidation and Oxygen Reduction Reactions in Alkaline Media
Authors: Meléndez-González P.C. , Sánchez-Castro Maria Esther , Alonso-Lemus Ivonne Liliana , Pérez-Hernández R. , Escobar-Morales Beatriz , Garay-Tapia A.M. , Rodríguez-Varela F.J.
Published: February 2020

The electrochemical stability and catalytic activity of 20 wt. % Pd-CeO2-NR/C (Pd:CeO2-NR 1:1 atomic ratio) and 20 wt. % Pd/C nanocatalysts for the Oxygen Reduction Reaction (ORR) and the Ethanol Oxidation Reaction (EOR) in 0.5 mol L-1 KOH is evaluated in this work. The nanocatalysts have been synthesized by the polyol method. The morphology and chemical composition of the synthesized Pd-CeO2-NR/C and Pd/C have been determined in a Field Emission Scanning Electron Microscope (FESEM) with an energy dispersive X-Ray detector. The results show a chemical composition close to the nominally expected. Meanwhile, the XRD analysis demonstrates the crystalline nature of the nanocatalysts with crystallite size of Pd-CeO2-NR/C and Pd/C of 11.8 and 7.9 nm, respectively. XPS analysis indicates mainly the presence of Pd0, Pd2+, and Pd4+ species on both electrocatalyst, as well as Ce3+ and Ce4+ in Pd-CeO2-NR/C. It has been determined that after accelerated degradation test (ADT, 3000 cycles between 0.6 and 1.0 V/RHE), the ECSA loss of Pd-CeO2-NR/C is of around 3 %, clearly smaller compared to 80 % in the case of Pd/C, which suggests a synergic effect between CeO2-NR and Pd that stabilizes the metallic nanoparticles. Evaluation by RRDE shows that Pd-CeO2-NR/C has a catalytic activity for the ORR similar to Pd/C in terms of onset potential of the ORR (0.98 and 0.94 V/RHE before ADT, respectively; 0.91 and 0.92 V/RHE after ADT, respectively). Nevertheless, Pd-CeO2-NR/C delivers higher mass and specific activities than Pd/C, with both nanocatalysts producing about the same amount of H2O2 (around 3 - 4.5 %). Meanwhile, the polarization curves of the EOR before ADT show a peak mass current density of 697.70 mA mgPd
-1 generated by Pd-CeO2-NR/C (at 0.86 V/RHE), higher than 665.66 mA mgPd
-1 obtained from Pd/C (at 0.92 V/RHE). After ADT, the mass current density increased by 1.6 and 1.4 times at Pd-CeO2-NR/C and Pd/C, respectively. The results show that Pd-CeO2-NR/C is a highly electrochemically stable bifunctional nanocatalysts with high catalytic activity for the ORR and the EOR in alkaline media, which make it a promising candidate for A-DEFCs applications.
Sulphur-Doped Ordered Mesoporous Carbon Hollow Spheres with High Catalytic Activity for the Oxygen Reduction Reaction and Exceptional Electrochemical Stability
Authors: Carrillo-Rodríguez J.C. , Alonso-Lemus Ivonne Liliana , de la Torre Saenz Luis , Escobar-Morales Beatriz , Garay-Tapia A.M. , Rodríguez-Varela F.J.
Published: February 2020

We reported the synthesis and characterization of the novel and less explored methanol-functionalized Sulphur-Doped Ordered Mesoporous Carbon Hollow Spheres (S-HWf) as metal-free electrocatalyst for the Oxygen Reduction Reaction (ORR) in alkaline media. The S-HWf was synthetized by the silica template-based method, using resorcinol and formaldehyde as carbon source. The doping was made in situ using 2-thiophenemethanol as sulphur source. The functionalization was carried out with methanol solution (0.5 mol L-1) with the aid of intermittent microwave heating. The catalytic activity of S-HWf was compared with that of non-doped Ordered Mesoporous Carbon Hollow Spheres (HW) synthetized by the same method.

The morphology of S-HWf and HW analyzed in a Field Emission-Scanning Electron Microscope (FE-SEM) resulted in rough hollow spheres. The diameter and wall thickness were ~304 and ~90 nm for HW, while for S-HWf were ~248 and ~50 nm, respectively. The use of 2-thiophenemethanol as dopant, had an important effect in the morphology. The chemical surface composition determined by X-ray Photoelectron Spectroscopy (XPS) included the presence of C, O, and Si for HW. In addition to these elements, S was also detected at S-HWf (0.4 at. %). The textural properties were determined by N2 adsorption/desorption measurements. S-HWf and HW showed a surface area of 1007 and 505 m2 g-1, respectively, with micro-mesoporosity. Analysis of the electrocatalysts by X-Ray Diffraction (XRD) showed their amorphous structure with low-intensity crystalline phases. Meanwhile, from Raman spectroscopy S-HWf exhibited better ordering in its structure due to a lower value in ID/IG the intensity ratio compared to HW. The catalytic activity of the electrocatalysts for the ORR was evaluated by Rotating-Ring Disc Electrode (RRDE) technique. S-HWf showed a higher performance than HW, with an onset potential of 0.88 V half-wave potential 0.81 V and a current density (j) of -1.49 mA cm-2 at 0.8 V (all potentials vs. RHE). Moreover, its electron transfer number was n= 3.9 with a H2O2 production of ~3%. Furthermore, after accelerated degradation tests (3000 cycles, between 0.6 and 1.0 V), S-HWf showed an improvement in catalytic activity with onset potential of 0.88 V, half-wave potential of 0.82 V and j= -1.69 mA cm-2 at 0.8 V. Also, its n was 3.9 with a production of H2O2 of ~2%.

In this study it was found that doping with sulphur and functionalizing with methanol have a positive effect on the catalytic activity for the ORR and the electrochemical stability of Ordered Mesoporous Carbon Hollow Spheres. The electrochemical behavior of the S-HWf electrocatalyst indicated that it is a potential candidate for Anion Exchange Membrane Fuel Cells (AEMFC) cathode applications.
Highly Active Binder Free Plasma Sprayed Non-Noble Metal Electrodes for Anion Exchange Membrane Electrolysis at Different Reduced KOH Concentrations
Authors: Razmjooei Fatemeh , Reißner Regine , Gago Aldo Saul , Ansar Asif
Published: February 2020

The production of hydrogen by the water electrolysis technique to provide a fossil fuel alternative energy source has attracted a plethora of attention among the other different methods in the context of sustainability, renewable energy source utilization and green technology.[1] Conventional alkaline water electrolyzer (AWE) offers many advantages compared with other systems. One of the major advantages of AWE over proton exchange membrane water electrolyser (PEMWE) is the replacement of conventional noble metal electrocatalysts with active, stable and relatively low-cost transition metal catalysts. However, AWE electrolyzers suffer from lower operational current density compared with their PEMWE counterpart. Like AWE, anion exchange membrane (AEM) electrolyzer does not require noble metal catalysts, which makes this technology much less expensive than PEMWE, while possessing the advantage of PEMWE. However, the electrochemical water splitting performance of AEM water electrolysis is still much lower than that of PEMWE. Focusing on this issue, the presented work aims at improving the performance of AWE and AEM electrolysers by developing cost effective non-noble electrodes on macro-porous transport layer (MPL) using the air plasma spray deposition method.[2] MPLs were fabricated by depositing Ni-graphite on porous substrates. Graphite was removed during particle in-flight forming a controlled porous layer. Electrodes were developed by plasma spraying of NiMoAl for cathode and NiAl for anode on top of the MPL followed by activation in which Al was partially leached out from layers of both electrodes using an alkaline solution. Electrochemical tests were conducted on half-cell in 6M KOH solution and then in the full cells for AWE and AEM in 6M and 0.3M KOH, respectively. The electrochemical performance is recorded via over-potential measurements, electrochemical impedance spectroscopy (EIS), cyclic voltammetery and polarization curve. With optimal combination of MPL and electrodes, current density of 0.5 Acm-2 at 1.80 V was recorded as the initial performance in 6M solutions for AWE using Zirfon separator and the current density of 0.31 Acm-2 at 1.80 V was recorded for AEM electrolyzer with more dilute KOH solution (0.3M) using an anion exchange membrane. 64 days of abusive testing was conducted for the AWE without measurable degradation in the performance in 6M KOH. The catalysts developed in this work will be promising in supporting the pursuit of cheap, affordable and ideal eco-friendly hydrogen fuel.

[1] F. Razmjooei, K.P. Singh, D.S. Yang, et al., Acs Catalysis, 2017, 7, 2381-2391.

[2] A.S. Gago, S.A. Ansar, B. Saruhan, et al., J Power Sources, 2016, 307, 815-825.
Ethanol/Formic Acid Blend As an Alternative Fuel for the Pd-Based Direct Formic Acid Fuel Cells
Authors: Ahmed Nashaat , Zahran Mohamed , Alnajjar Taher , El Sawy Ehab N
Published: February 2020

Sustainable energy production is necessary for the next generation. Therefore, it is important to develop/improve a new series of energy technologies that are clean and efficient. A major interest is given to low-temperature fuel cells as an energy conversion device for different applications such as portable devices and electric vehicles. Formic acid is being analyzed and considered to be one of the most promising fuels that could replace methanol in direct liquid fuel cells for portable power applications. The electro-oxidation of formic acid takes place through a dual reaction pathway, dehydrogenation (direct pathway) and dehydration (indirect pathway). In the indirect pathway, a strongly adsorbed CO is produced which blocks the surface, while in the direct pathway CO2 is directly produced. As the direct pathway requires fewer surface atoms than the indirect pathway,1 one of the strategies to enhance the catalytic activity and stability of the catalyst is to modify its surface with ad-atmos2 or adsorbed species, making the direct pathway more favorable (third body or ensemble effect).3

References:

M. Neurock, M. Janik, and A. Wieckowski, Faraday Discuss., 140, 363–378 (2008).

A. Ferre-Vilaplana, J. V. Perales-Rondon, J. M. Feliu, and E. Herrero, Acs Catal., 5, 645–654 (2015).

E. Leiva, T. Iwasita, E. Herrero, and J. M. Feliu, Langmuir, 13, 6287–6293 (2002).

In this work, the influence of using a blend of ethanol (EtOH) and formic acid (FA) on the catalytic activity of Pd towards the formic acid oxidation is explored in 0.1 M H2SO4 at room temperature, using a commercial 40% Pd/C catalyst. It is known that Pd is inactive towards EtOH oxidation and very active towards FA oxidation, and hence the ethanol oxidation contribution in the case of the blend is neglected. It was found that with increasing the ethanol concentration the direct pathway becomes more favorable as indicated by the ratio between peak currents of the direct and indirect pathways in the forward scan.
Quantifying the Effect of Ruthenium Contamination on the ORR Activity of DMFC Cathode Catalyst
Authors: Olewsky Chen , Ripenbein Tania , Keinan Liz , Ben Yehuda Ohad , Shviro Meital , Kaplan Dmitri , Peled Emanuel
Published: February 2020

Direct methanol fuel cell (DMFC) technology is a promising energy source for portable, stationary and light transportation applications in the range of several watts and up to a few kW. Currently, one of the main drawbacks preventing widespread commercialization of DMFCs is their relatively short lifetime, up to a few thousands of hours at best. Usually a DMFC lifetime is not defined by a complete failure of the cell but by a slow and continuous degradation of the performance, up to the point when the delivered power is too low for the intended application. Several different degradation mechanisms contribute to this degradation [i], one of them is ruthenium contamination of the cathode catalyst [ii] following ruthenium dissolution from the anode PtRu catalyst and its cross-over to the cathode [iii].

The aim of our research is to quantitatively measure the effect of ruthenium contamination on the ORR performance of the cathode catalyst. For this purpose, different amounts of ruthenium (equivalent of 0.15-3 monolayers) were deposited on commercial Pt/C nanopowder to simulate ruthenium deposition on the cathode during a DMFC operation. The ruthenium-contaminated Pt/C powders were prepared using electroless polyol reduction method with methanol as the reducing agent. Johnson Matthey HiSPEC 8000 50%Pt/C was chosen to simulate a DMFC cathode catalyst. The composition, particles size and structure of these RuPt/C powders were verified by TGA, SEM-EDS, XPS, HR-TEM and STEM-EDS. Electrochemical characterization was performed with the use of cyclic-voltammetry and rotating–disk–electrode (RDE) techniques and compared to that of HiSPEC 8000. It was found that already at 0.25 equivalent monolayer of ruthenium (EDS %At Pt92Ru8, XPS %At Pt90Ru10) there is a massive, more that 25%, decrease in ORR specific activity of the commercial Pt/C catalyst. This decrease grows rapidly up to a complete inhibition of ORR at approximately 1 equivalent monolayer of ruthenium (EDS %At Pt64Ru36, XPS %At Pt50Ru50). The obtained results quantitatively show that ruthenium contamination indeed has a major role in the performance degradation of DMFCs.

[i] A. Mehmood, M. A. Scibioh, J. Prabhuram, M. G. An, H.Y. Ha, Journal of Power Sources, 2015, 297,224–241

[ii] L. Gancs, B. N. Hult, N. Hakim, S. Mukerjee, Electrochem. Solid-State Lett., 2007, 10, 9, B150

[iii] P. Piela, C. Eickes, E. Brosha, F. Garzon, P. Zelenay, Journal of The Electrochemical Society, 2004, 151 (12), A2053–A2059
Making Copper and Alloyed Single Crystal Beads By Oxygen-Hydrogen Flame in Air and Boosting the Electrocatalytic Activity Toward Formaldehyde Oxidation By the Factor of 12 with 1.5 % of Ni
Authors: Liao Weicheng , Chen Yi-wei , Yau Shuehlin , Shyue Jing-Jong
Published: February 2020

This work shows that it is feasible to prepare chemically pure or bimetallic, non-precious metal (Cu, Ni, Co) single crystal electrodes by melting the end of a polycrystalline metal wire in the air by a tactfully designed oxygen-hydrogen torch. The structures and chemical compositions of the as-prepared Cu and CuNi beads were characterized by X-ray photoelectron spectroscopy (XPS). Obtained results show that Cu and the CuNi single crystal beads are free of oxide in the bulk and Cu to Ni molar ratio is 98.5:1.5 in the CuNi bead. After flame annealing, the thickness of cuprous oxide on the (111) surface is less than 10 Å. The (111) planes of Cu and Cu/Ni electrodes are exposed to study their electrocatalysis toward the oxidation of formaldehyde (HCHO) in 0.1 M KOH, which is relevant to the development of fuel cells, hydrogen carrier and the removal of HCHO in waste water. The HCHO fuel cell employs Cu/Ni anode can have multiple advantages. First, the cell potential for HCHO/CuNi anode is ~ 0.5V more greater than a typical CH3OH/Pt anode if the same cathode is used. Second, Cu and Ni metals are the inexpensive and abundant. Third, the aqueous HCHO has a relatively lower vapor pressure than methanol. Fourth, paraformaldehyde, the source of HCHO, is a solid at room temperature, which makes it easy to be transported and stored. Although bulk Ni is inactive toward HCHO oxidation, a tiny Ni in the Cu electrode increases the exchange current density, due to HCHO oxidation, by 12 times. The durability of Cu(111) and Cu98.5Ni1.5(111) electrode in catalyzing HCHO oxidation is researched by stepping the potential from their OCP (-0.9 and -1V vs. Ag/AgCl) to -0.4 and -0.54V. For Cu(111), the current surges after the switch of potential, followed by an exponential drop from 0.9 to 0.06 mA/cm2 within 100 s. For Cu98.5Ni1.5, the current decrease to 1/4 (1mA/cm2) of its original value in 300 sec and then fluctuates between 0.8 and 0.7 mA/cm2. The activity is restored after the interface is refreshed by removing and re-immersing the electrode in the electrolyte. The kinetics of HCHO oxidation at Cu98.5Ni1.5 and Cu(111) electrodes are scrutinized by conducting voltammetry in 0.1 M KOD/KOH + 0.1 M HCHO. The current observed at Cu98.5Ni1.5 in KOD is markedly lower than that recorded in KOH; whereas no effect is seen with Cu(111). This contrast implies that a cleavage of a O-D bond is involved in the rate-determining step of HCHO oxidation at Cu98.5Ni1.5, but not at the Cu(111) electrode.

Figure 1
Molecular Dynamics Simulation on Quaternized Ammonium Poly (ether ether ketone) for Anion-Exchange Membrane Fuel Cells
Authors: Chen Sian , Wang Haining , Zhang Jin , Lu Shanfu , Xiang Yan
Published: February 2020

Poly (ether ether ketone) (PEEK) is a robust engineering plastic with good thermal and chemical stability. The quaternized ammonium (QA) functionalized PEEK provides anion transfer capacity for anion-exchange membrane fuel cells (AEMFC), because the introduction of hydrophilic QA groups or QA-based side chains. QA-PEEK membrane has been a promising solution for AEMFC in recent years thanks to the improvement of synthesis method1-3 and the abundance of grafting groups4,5. The divergence of hydrophilicity between backbones and side chains of QA-PEEK could result in microphase separation due to the spontaneous aggregation. In our previous work5, we reported the ions conductivity of two QA groups functionalized PEEK (GQ-PEEK, Fig.(a)) is higher than that of one QA groups (SQ-PEEK, Fig.(a)) under same grafting degree (GD). However, the mechanism of the improved conductivity still needs more investigation because various parameters could affect the ions conductivity, for example, ion exchange capacity (IEC), micro-phase separation, as well as effective ions diffusion coefficient.

Generally, the micro-structure of the membrane and ions transportation process could be effectively investigated by molecular dynamics simulations6,7. In the present work, we carried out molecular dynamics simulation to investigate the microphase separation and transportation process (H2O and OH-) of SQ-PEEK and GQ-PEEK respectively. The calculated structure factor (Fig.(b)) reveals the possible microphase separation in both membrane. The cluster size of GQ-PEEK (~3.69 nm) is slightly larger than that of SQ-PEEK (~3.24 nm), which is in consistent with the TEM results (Fig.(c)). Meanwhile, the self-diffusion coefficients (Fig.(d)) of both H2O and OH- in GQ-PEEK have no obvious difference than those in SQ-PEEK. Therefore, the increased conductivity of GQ-PEEK should attribute to the increased IEC in comparison to SQ-PEEK. This work provides a deeper understanding of anion-exchange membrane for fuel cells.

Reference

(1) Jasti, A.; Prakash, S.; Shahi, V. K. Journal of Membrane Science
2013, 428, 470.

(2) Han, J.; Peng, H.; Pan, J.; Wei, L.; Li, G.; Chen, C.; Xiao, L.; Lu, J.; Zhuang, L. Acs Applied Materials & Interfaces
2013, 5, 13405.

(3) Yan, X.; He, G.; Gu, S.; Wu, X.; Du, L.; Zhang, H. Journal of Membrane Science
2011, 375, 204.

(4) Si, J.; Wang, H.; Lu, S.; Xu, X.; Peng, S.; Xiang, Y. Journal of Materials Chemistry A
2017, 5, 4003.

(5) Si, J.; Lu, S.; Xu, X.; Peng, S.; Xiu, R.; Xiang, Y. Chemsuschem
2014, 7, 3389.

(6) Pan, J.; Chen, C.; Li, Y.; Wang, L.; Tan, L. S.; Li, G. W.; Tang, X.; Xiao, L.; Lu, J. T.; Zhuang, L. Energy & Environmental Science
2014, 7, 354.

(7) Lyu, K.; Peng, Y.; Xiao, L.; Lu, J.; Zhuang, L. Journal of Energy Chemistry
2018.

Figure 1
Hydroxide and Carbon Dioxide Transport Properties in High Performance Poly(norbornene) Anion Exchange Membranes
Authors: Huang Garrett , Mandal Mrinmay , Kohl Paul A
Published: February 2020

Alkaline exchange membrane (AEM) fuel cells are an alternative to more conventional proton exchange membrane (PEM) fuel cells and electrolyzers. In recent years, anion conducting polymer membranes have achieved stability and ionic conductivity competitive with Nafion. Lightly cross-linked AEMs based on vinyl addition polymerized norbornene have record-high hydroxide conductivity (212 mS/cm) with <1% performance degradation over 1,200 hours in 1 M NaOH at 80 °C. Composite versions of these AEMs have also been used to construct membrane electrode assemblies for alkaline fuel cells with a peak power density of 3.4 W/cm2, 70% higher than the previous record for this type of system to date.

The presence of carbon dioxide in air, or carbonate in the electrolyzer water feed impacts device performance because of the high pH of the membrane. Carbon dioxide in the fuel cell air stream poses a practical limitation for large scale deployment of alkaline fuel cells. AEM fuel cell tests are often operated with oxygen or CO2-free air to avoid the complications of carbonate formation, which inherently lowers conductivity and the overall fuel cell performance. The focus of this talk is on the transport of hydroxide, bicarbonate and carbonate in poly(norbornene) membranes. The transport properties of CO2 have been characterized and relationships between the diffusivity and solubility of CO2­ in the polymer membrane in parallel with the in situ flux of carbonate ions through the AEM have been studied.

Financial support provided by the ARPA-E IONICS program for G.H. and M.M. is gratefully acknowledged.
Alkaline Exchange Fuel Cell Membrane Ionomers Containing Spirocyclic Repeat Units in an All Carbon Backbone for Enhanced Durability
Authors: Strasser Derek , Meek Kelly M , Neyerlin Ami , Antunes Christopher M , Pivovar Bryan S.
Published: February 2020

Alkaline exchange membrane fuel cells (AEMFC)s continue to gain interest as a potential lower cost alternative to the commercially available proton exchange membrane fuel cells (PEMFC)s. Recently there have been significant advances in the performance of AEMFC systems achieving greater than 1 1-2, albeit with PGM catalysts. However, the incorporation of non PGM catalyst materials will significantly reduce costs. One of the more significant challenges to the commercialization of AEMFCs is demonstrating long term durability under operating conditions and over startup/shutdown cycles. Improving the durability of the ionomers employed in alkaline exchange membranes and catalyst ink formulations will enhance the long term durability of AEMFCs.

Enhancing the durability of alkaline ionomers has focused on the installation of more stable cationic head groups3. Previous research has demonstrated the incorporation of spirocyclic repeat units into multiblock copolymers of polysulfone4. The research presented demonstrates the incorporation of the spirocyclic polymer poly(diallylpiperidinium hydroxide) into an all carbon backbone of hydrophobic/hydrophilic block copolymers. The synthesis, characterization and performance is pesented.

Omasta, T. J.; Peng, X.; Miller, H. A.; Vizza, F.; Wang, L.; Varcoe, J. R.; Dekel, D. R.; Mustain, W. E., Beyond 1.0 W cm-2 performance without platinum: the beginning of a new era in anion exchange membrane fuel cells. J. Electrochem. Soc. 2018, 165 (15), J3039-J3044.

Omasta, T. J.; Zhang, Y.; Park, A. M.; Peng, X.; Pivovar, B.; Varcoe, J. R.; Mustain, W. E., Strategies for Reducing the PGM Loading in High Power AEMFC Anodes. J. Electrochem. Soc. 2018, 165 (9), F710-F717.

Marino, M. G.; Kreuer, K. D., Alkaline Stability of Quaternary Ammonium Cations for Alkaline Fuel Cell Membranes and Ionic Liquids. ChemSusChem 2015, 8 (3), 513-523.

Strasser, D. J.; Graziano, B. J.; Knauss, D. M., Base stable poly(diallylpiperidinium hydroxide) multiblock copolymers for anion exchange membranes. J. Mater. Chem. A 2017, 5 (20), 9627-9640.
(Invited) Enabling Cost Effective Hydrogen at Low Temperatures
Authors: Mukerjee Sanjeev , Kolla Praveen , Jia Qingying , Kendrick Ian , Yan Yushan
Published: February 2020

This presentation will focus on durable, high-performance materials and interfaces for advanced water splitting, enabling a clear pathway for achieving <$2/KgH2 (on scale) with efficiency of 43 KWh/Kg using anion exchange membrane interface. Advances via fundamental understanding of both hydrogen and oxygen evolution reactions (HER/OER) leading to novel materials will be in conjunction with critical improvements in membrane and ionomers and gas evolution electrodes with corresponding characterization and testing. Progress towards these goals under a three-year multifaceted and comprehensive effort will be described wherein Northeastern University (NEU) will present catalyst development and characterization (both in situ and ex situ). University of Delaware (UD) will showcase improvements in ionomer and membrane materials. In addition, close collaboration with National Laboratory partners with Lawrence Berkeley National Lab (LBNL) participating in multiscale modeling and computation in close concert with Sandia National Laboratory (SNL) providing MD simulations of the membrane catalyst interface and National Renewable Energy Laboratory (NREL) providing advanced ionomers, durability protocols and validation will be described.

Anion exchange membrane electrolyzers (AEMELs) are ideally suited with a low-cost profile enabled by platinum group metal (PGM)-free catalysts, low fluorine content membranes, and a less corrosive environment for cell separators. This presentation will showcase state of the art stable, high-conductivity, and high-strength AEMs, stable and active PGM-free catalysts for hydrogen and oxygen evolution reaction (HER/OER), and high performance electrode architectures that together can unlock the cost advantages of AEMELs. If successful, the developed technology can meet FCTO efficiency targets, delivering carbon-neutral hydrogen at $2/kg while simultaneously enabling higher penetrations of wind and PV electricity on the grid.

The overall goal is cell level performance of 1.62 V at 1 A/cm2, which meets the FCTO efficiency target of 43 kWh/kg. Component performance targets have been established using a porous electrode model to support the overall cell performance target. This is at the modeled scale of 50,000 kg/day and operating at 1 A/cm2 resulting in hydrogen cost at $2.15, $1.82, or $1.76/kg, respectively (2, 20, 200 plants). In the low-volume manufacturing case, it is still possible to meet the cost target by operating near 2 A/cm2, sacrificing some efficiency.
(Invited) The Key Processing Issues and Their Solutions for High-Quality Perovskite Solar Cells
Authors: Sarvari Hojjat , Nasseri Mohsen , Park So Min , Kamali Poorya , Strachan Douglas , Graham Kenneth , Singh Vijay , Chen Zhi David
Published: February 2020

We report the fabrication of cesium-doped mixed cation perovskite solar cells (PSCs) (FTO/c-TiO2/mp-TiO2/Perovskite/spiro-OMeTAD/Au). A few key processing issues and their solutions are introduced. The smooth, shiny, and dark perovskite film is deposited by using the anti-solvent method through spin-coating. First, the deposition of a pinhole-free c-TiO2 layer with a smooth surface is critical. Here, we introduce a new TiO2 solution using titanium isopropoxide (TiO2 99.99%) to tackle the issue the issues related to the conventional TiO2 solutions. Compared to the conventional one, the spin-coating of the new solution provides a pinhole-free, efficient hole-blocking layer without cracks and still cheaper and quicker than the latter one. Highly reproducible PSCs with an average power conversion efficiency (PCE) of 15.4% are fabricated using this solution compared to the conventional solution utilizing both spin-coating and spray pyrolysis with average PCEs of 10.6% and 13.78%, respectively. The anti-solvent method was usually used with chlorobenzene (CBZ), but CBZ cannot dissolve the Li-TFSI particles which may be present on the surface of mp-TiO2 right after Li-doping process. In this case, we should use a solvent that can dissolve the Li-TFSI particles completely. Both diethyl ether (DEE) and the mixed of CBZ and DEE (volume ratio of 4:1) can dissolve the Li-TFSI particles easily. It improves the size of perovskite particles which leads to lower density of defects in the film compared to the one with smaller particles. The overall PCE is enhanced to 15.9% for samples with CBZ:DEE compared to the PCE of 14.76% for samples with CBZ in the same processing conditions. Moreover, a thin layer of silver (Ag) is introduced as the interlayer between the hole transport layer (HTL) and the Au. We deposited a 2-5nm of Ag on top of the HTL followed by 80 nm of Au. By this, the adhesion of the Au layer to the device is improved according to the simple tweezer tool test. A pure Au film can easily come off from the surface of the HTL, however, the Au films with 2-5nm of silver buffer layer show strong adhesion to the device. Interestingly, the employment of 2nm silver film improved the current density and, finally the PCE of the devices by both improving the adhesion of the back electrode onto the device and increasing the light reflection in the PSC. Finally, a reproducible fabrication procedure of PSCs with an average PCE of 16.5%, and a maximum PCE of 17.43% for an active area of 0.08 cm2 is achieved.
Rapid Fabrication of Thin Films for Perovskite Solar Cells
Authors: Ghahremani Amir Hossein , Druffel Thad
Published: February 2020

Thin film organic-inorganic perovskite photovoltaics have undergone rapid performance improvement and has therefore provided the researchers a great tendency towards large scale manufacturing through cost-effective automated manufacturing. The automotive techniques include three main processes of prior preparation processing, the main deposition step, and a post process thermal annealing to provide the final product with superior quality. Successful fabrication of supreme thin film photovoltaics requires the application of instruments and techniques which can provide rapid manufacturing to meet the demanding market needs, and the use of cheap and versatile fabrication methods to provide the lowest final product price with respect to maximum device quality. In this manuscript we address the quality of the deposited thin films, particularly for thin film perovskite solar cells (PSCs), after being deposited and annealed through the favorable roll to roll automotive steps. These techniques include the use of ultrasonic spray and slot-die mechanisms to coat the thin films, followed by rapid annealing of the thin film materials through rapid photonic annealing. The morphology and phase purity of the deposited films will be illustrated through characterization techniques of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) patterns. This study can provide researchers with better understanding of thin film fabrication through automated manufacturing, particularly through roll to roll, and provide them an opportunity for better selection of the methods towards optimal thin film manufacturing.
Adhesion Force Degradation in Degraded Single Junction Amorphous Silicon Module (a-Si:H)
Authors: Osayemwenre Gilbert
Published: February 2020

The adhesion force between two interface layers in amorphous silicon solar (a-Si:H) module plays a crucial role in its carrier transport across the various interfaces. The quality of each interface layer depends on its mechanical properties. In other words, its mechanical property influences the performance of a-Si:H module. In this study, two mechanical properties of a PV module which include interfacial adhesion, and deformation across layers were studied. The binding force between interfaces is susceptible to defects as a PV module begins to degrade. Therefore, the changes that occur in the adhesion force of a degraded a-Si:H is a proper tool for degradation analysis. Thus, this paper deals with the microstructure, defects, and mechanical properties of a-Si:H module. The aim of the study was to cross examine which region of the degraded module was more prone to mechanical degradation. The degradation of adhesive strength results to mechanical defects, which can be observed as microstructural defects when mapped with Scanning Probe Microscope (SPM). The dearth of information on the correlation between these microstructural defects, and adhesive degradation is the motivations for this study. SPM was used to measure the adhesion force between interface layers, at a rate of 0.701Hz. In order to achieve uniformity in the results, each scanning was 512 lines for a retraced direction and the mapping was captured in an upward direction. The study shows that adhesion force exhibits a higher decay in the intrinsic layer interface p/i than in other regions. In addition, the sample from the affected region demonstrated a higher decrease in its adhesion force and a higher deformation. Mechanical degradation at nanoscale level enhance interfacial delamination, which can potentially result to premature failure. Thus, an in-depth comprehension of adhesive degradation is essential in degradation analysis.
Spray-Deposited Al2O3 for Rear Passivation and Optical Trapping in Silicon Solar Cells
Authors: Shin Woo Jung , Huang Wen-Hsi , Tao Meng
Published: February 2020

Si passivated emitter rear contact (PERC) are expected to become the dominant cell technology in the near future [1]. In PERC cells, a thin layer of Al2O3 is deposited on the rear of the Si cell to reduce rear surface recombination on p-type Si by chemical and field-effect passivation [2]. Optically the Al2O3 film is supported by a thicker SiNx layer stacked on Al2O3, and the low refractive index of SiNx improves light trapping in the Si cell by rear reflection [3]. In commercial production, the Al2O3 film is prepared by atomic layer deposition (ALD). ALD is a slow process and the precursor for Al2O3, Al2(CH3)6, is expansive and pyrophoric. For these reasons the thickness of the Al2O3 film in PERC cells is limited to ~10 nm and the 80-nm SiNx layer is deposited on Al2O3 by plasma-enhanced chemical vapor deposition (PECVD). It is noted that the refractive index of Al2O3 is lower than that of SiNx, 1.6 vs. 2.0 [4,5], so a thicker Al2O3 film on the rear of the PERC cell should provide better rear passivation and optical trapping than an Al2O3/SiNx stack. This requires a low-cost process to deposit thicker Al2O3 on Si.

In this talk, we report the suitability of spray-deposited Al2O3 for rear passivation and optical trapping in Si PERC cells. Electrical, optical and structural properties of spray-deposited Al2O3 are investigated and compared to the industrial standard ALD Al2O3/PECVD SiNx stack. It was found that spray-deposited Al2O3 has a negative charge density of 3.19×1012 cm–2 for an 80-nm film, indicating that spray-deposited Al2O3 can serve as the passivation layer. Optical properties of spray-deposited Al2O3 are identical to the ALD Al2O3/PECVD SiNx stack, suggesting that spray-deposited Al2O3 can also serve as the optical trapping layer. It was also found that spray-deposited Al2O3 is crack and pore free, and its surface roughness has a root-mean-square value of 0.42 nm for an 80-nm film. Spray-deposited Al2O3 is amorphous and its composition is slightly Al rich. The resistivity and breakdown field of 80-nm spray-deposited Al2O3 are ~1014 Ω-cm and 3.28 MV/cm, respectively. These properties suggest that spray-deposited Al2O3 is a promising candidate to replace the ALD Al2O3/PECVD SiNx stack in Si PERC cells.

[1] C. Roselund, International Technology Roadmap for Photovoltaic (ITRPV), 7, 21, (2016).

[2] N. Batra, J. Gope, R. Singh, J. Panigrahi, S. Tyagi, P. Pathi, S. K. Srivastava, C. M. S. Rauthan, P. K. Singh, Phys. Chem. Chem. Phys., 16(39), 21804 (2014).

[3] B. Vermang, H. Goverde, L. Tous, A. Lorenz, P. Choulat, J. Horzel, J. John, J. Poortmans, R. Mertens, Prog. Photovolt. Res. Appl., 20(3), 269 (2012).

[4] M. D. Groner, F. H. Fabreguette, J. W. Elam, and S. M. George, Chem. Mater., 16(4), 639 (2004).

[5] J. Schmidt and M. Kerr, Sol. Energy Mater. Sol. Cells, 65(1-4), 585 (2001).
(Invited) Advances in Coating Technology for Improving Electrode Manufacturing
Authors: Hellring Stuart D.
Published: February 2020

Although current electrode manufacturing technology produces reliable cells for lithium ion batteries, formulation composition and process engineering limit the electrode cost and performance range. These manufacturing limits can manifest in several ways including safety issues, toxic material exposure, slurry inventory management, low production rates, as well as costly downstream and support processes. Performance can suffer from energy and power density limits, short cycle life, and costly material components, among others. By improving electrode coating technology, advances are centered on many of the core issues that limit the growth of lithium ion batteries into less traditional applications such as transportation and grid storage. Formulation chemistry and process improvements for cathode electrode production will be presented with a focus on commercialization targets for emerging energy storage markets for lithium ion batteries.
Characterizing Lithiation/Delithiation of Thick Electrodes without Binders and Conductive Additives Using Neutron Imaging
Authors: Koenig Gary , Nie Ziyang , Ghosh Dipankar , Parai Rohan
Published: February 2020

The advantages of thick electrodes in improving energy density at the cell level has been reported in many lithium-ion battery papers. Thick electrodes increase energy density by reducing the fraction of the cell dedicated to inactive components, in particular current collectors and separators. However, thick electrodes increase electron and ion transport path lengths through the electrode which increases cell resistance and can result in limited current densities of battery operation.

In this presentation the fabrication and characterization of cells with thick electrodes will be described. These electrodes are produced via hydraulic pressing and mild thermal treatment of active material powders as opposed to conventional casting of composite slurries. These electrodes thus have no binders or conductive additives, which would be expected to increase the diffusion of ions through the electrolyte-impregnated void regions within the electrode. However, these all active material electrodes can now have multiple processes that might limit their rate of charge/discharge, including transport of ions through the electrode microstructure, transport of ions through the solid active material particles, and transport of electrons through the all active material electrode matrix to the current collector. To provide insights into the processes that are limiting the current density in the high energy electrodes, we will describe the use of neutron imaging. Neutron imaging is highly sensitive to the lithium concentration within the battery cell, and thus regions undergoing lithiation/delithiation can be interrogated in operando during charge/discharge of the cell. The lithiation/delithiation profiles provide insights into what process limits the cell and opportunities to improve the performance of these thick electrodes fabricated with less common processing routes.
(Invited) Primary Electrodeposition of Lithium Metal for Secondary Batteries
Authors: Steingart Daniel , Chang Wesley , Park Jeung Hun
Published: February 2020

The secondary lithium metal system is the ultimate negative electrode given its phase, redox potential and mass. To maximize the energy density of a cell the lithium metal should be in coulombic balance with the cathode of choice, but the large scale manufacturing of thin lithium foils remains a challenge. In this presentation we will review the programmers and challenges of primary production of lithium foil directly from lithium salt and oxides, and compare the efficacy of these films to thermal and chemical processing routes.
(Invited) Structure Design and Property Enhancement of Electrode Materials of Lithium-ion Battery
Authors: Sun Shi-Gang
Published: February 2020

is communication will report our recent progresses made on the design and synthesis of electrode nanomaterials of lithium ion battery for efficient energy storage.

Lithium-ion batteries (LIB) are widely used today. The fast development of high-technologies (such as 5G and artificial intelligence (AI)) and electric vehicles demands increasing as much as possible energy and power density of LIBs. The key issue is to develop electrode nanomaterials with high capacity and high rate property, as the property of both anode and cathode nanomaterials is determined by their structure, especially the surface structure which relates to the energy barrier of surface reaction and the density of lithium ion transportation. Based on a thorough analysis of structure-functionality, we have achieved to design and tune the structure and property of electrode nanomaterials, including anode of metal oxides (such as Co3O4, MnO) and cathode of lithium rich oxide, NCM and Layered/Spinel heterostructure nanomaterials. All the designed and well-controlled electrode materials were tested in LIB cells, and superior capacity, high rate property and excellent cycleability were confirmed.

Acknowledgements: The study was supported by NSFC (21621091) and the MOST (2016YFB0100202).

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How Transition Metals Facilitate Charge-Transfer through the SEI in Li-Ion Batteries
Authors: Harris Oliver Clyde , Tang Maureen H
Published: February 2020

Transition metal dissolution from a high-voltage Li-ion battery cathode accelerates capacity fade leading to unacceptably short battery lifetimes. After dissolution, metals like Mn, Ni, and Co deposit at the carbon anode and disrupt the formation and performance of the solid-electrolyte interphase (SEI), a vital battery interface responsible for protecting the electrolyte from the highly reductive anode. SEI contamination by metals results in continual Li loss and uncontrolled SEI growth, culminating in severe capacity decay. Fundamental understanding of the role of each metal in undermining SEI passivation is necessary to mitigate this degradation and to enable commercialization of high-voltage Li-ion cathodes.

In this work we interrogate the effects of three transition metals (Mn, Ni, and Co) on charge-transfer through the SEI via in-situ electrochemical characterization. Our approach is to grow an SEI in metal-contaminated electrolyte and then characterize the film via rotating disk electrode voltammetry. Redox mediators deconvolute through-film transport and reaction kinetics to determine physical charge-transfer mechanisms. We find that each metal disrupts the electronic properties of the SEI far more than the morphological properties, and that Mn-contamination is the most detrimental of the three metals. We compare charge-transfer mechanisms based on electron tunneling across the SEI and electrocatalytic metal cycling between redox states and compare experiments to microkinetic models of each mechanism. Our results indicate that reaction thermodynamics and kinetics do not fully capture why Mn facilitates faster through-film charge-transfer than Ni or Co. This suggests that differences in coordination environment between transition metals embedded in the SEI are responsible for the more aggressive disruption by Mn, offering insight into mitigation approaches to inhibit accelerated capacity fade.
Structure and Electrochemistry of SiOx Made By Reactive Gas Milling
Authors: Cao Yidan , Bennett J. Craig , Dunlap R. A. , Obrovac Mark N
Published: February 2020

SiO
x
is a promising Li-ion battery negative electrode material because of its high capacity and unique microstructure that leads to good cycle life. However, SiO is typically made by high temperature methods that are expensive and difficult to realize, especially at lab scale. Here, SiO
x
negative electrode materials were synthesized by ball milling Si in air. This method allows efficient control of oxygen content, as shown in Figure 1a and results in a similar microstructure as a commercially purchased SiO.

XRD and TEM results show that the SiOx prepared by ball milling in air are composed of nanocrystalline Si embedded in an amorphous silicon oxide matrix (Figure 1b). The very low initial coulombic efficiency (ICE) of conventionally made SiO (measured here to be ~55% for Aldrich SiO) is one of its major drawbacks. In contrast, reactive gas milled SiO
x
have much higher reversible capacities (>1500 mAh/g) and higher ICE values (>70%). Reactive gas milled SiO
x
has a number of attractive features: an inexpensive and simple synthesis process, high capacity, high ICE, high thermal stability (stable microstructure at 800 °C, Figure 1c), and a special microstructure that protects Si from reaction with electrolyte, resulting in excellent cycling performance (Figure 1d).

Here a detailed study will be presented describing SiO
x
synthesis by reactive gas milling, thermal properties, and its electrochemical performance in relation to its composition and microstructure.

Figure 1