bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Insights of the pH Effect on Hydrogen Evolution and Oxidation Reactions Mechanisms in Alkaline Solutions
Authors: Liu Ershuai , Mukerjee Sanjeev , Jia Qingying 
Published: May 2020

The sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions than in acid remains elusive. Elucidation of the mechanisms of the HER/HOR in alkaline can not only deepen our understandings of alkaline electrochemistry, but also help to rationalize the design of highly active catalysts for alkaline fuel cells and electrolyzers. Herein, we investigate the HER/HOR kinetics of a variety of catalysts including monometallic catalysts (Ni, Pt, Ru, Au) and bimetallic catalysts (NiMo, Pt-M) by comparing their HER/HOR performance in 0.1 M KOH and 1 M KOH. We found that the HER/HOR kinetics of these systems are not always slower in 1 M KOH (pH =14) than in 0.1 M KOH (pH = 13). These observations do not follow the general trend that the HER/HOR kinetics of a wide range of elements slows down with increasing pH1. We propose to resolve this inconsistency by pointing out that the pH is only one of the factors that affect the transport of the HER/HOR intermediates (hydroxyl for HER, Had for HOR) throughout the double layer region, among other factors such as the oxophicility of the surface sites, the cation environment, etc. These factors co-determine the HER/HOR kinetics of catalysts (such as Pt/C) that is limited by the transport of reactions throughout the double layer region. As the electrolyte changes from 0.1 M KOH to 1 M KOH, the pH shifts from 13 to 14, slowing down the HER/HOR kinetics. Meanwhile, the K+ concentration increases one order of magnitude, which promotes the transport of OHad according to the hard-soft acid-base (HSAB) mechanism we proposed recently2, thereby improving the HER but not the HOR until the K+ saturates. The change of the HER/HOR kinetics of a catalyst as the electrolyte changes from 0.1 M KOH to 1 M KOH is a counterbalance between these two effects, and thus varies case by case.

Acknowledgements.
This work was supported by the Department of Energy (DOE) under award number DE-EE0008082, Office of Naval Research (ONR) under award number N00014-18-1-2155 and the Graduate Thesis/Dissertation Grant of Northeastern University. This research used beamline 7-BM (QAS) and 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

References

(1) Herranz, J.; Durst, J.; Fabbri, E.; Patru, A.; Cheng, X.; Permyakova, A. A.; Schmidt, T. J. Interfacial Effects on the Catalysis of the Hydrogen Evolution, Oxygen Evolution and CO2-Reduction Reactions for (Co-)Electrolyzer Development. Nano Energy
2016, 29, 4–28.
(2) Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q. Unifying the Hydrogen Evolution and Oxidation Reactions Kinetics in Base by Identifying the Catalytic Roles of Hydroxyl-Water-Cation Adducts. J. Am. Chem. Soc.
2019, 141 (7), 3232–3239.
Catalytic Growth of MWCNTs & Carbon Onions By Chemical Vapor Deposition on Nickel-Silica Nanocomposite Prepared Via Alcogel Electrolysis and Electrochemical Catalytic Study Towards OER
Authors: Ali Zulfiqar 
Published: May 2020

Novel carbon nanostructures are desired for development of alternative to noble metal based electrocatalyst for sustainable energy technologies like production of hydrogen. In this work first nickel-silica nanocomposite with a particles size of about 20 nm has been formed by alcogel electrolysis and employed for catalytic growth of carbon nanostructures by CVD at 650-750°C using alcohol precursor diluted by argon followed by electrocatalytic study towards oxygen evolution reaction (OER) in 1M KOH solution has been carried. The carbon nanotubes of two different diameters, i.e. 10-30 nm and about 100-300 nm are seen at synthesis temperature of 650°C. The larger tubes are replaced by irregular structures and carbon onions at 750°C, with almost negligible nanotubes at the latter temperature. The diameter distribution of onion like carbon is found to be in the range 50-700nm. Shift from thicker nanotubes to onions may be partly attributable to higher diffusion rates of carbon that result in complete coverage of larger nanoparticles without allowing an open end to continue the growth of a nanotubes. Small radius of curvature and extra-ordinary distortion required for carbon onions has not allowed them to grow on small nanoparticles.
Key words: Nickel-silica Nanocomposite, Carbon Nanotubes (CNTs), Carbon onions, Chemical Vapor Deposition (CVD), OER
Synthesis of Binder Free NiFeOSe/Ni Foam Catalyst for Oxygen Evolution Reaction and Charge Storage Performance
Authors: Sahoo Malaya Kumar , Rao Ranga 
Published: May 2020

Design of cost-effective electrocatalysts and supercapacitor electrode materials with enhanced functionalities has great potential in energy conversion and storage processes. Here direct growth of NiFeOSe on Ni foam is described and its catalytic performance for oxygen evolution reaction (OER) was evaluated. This novel noble-metal-free NiFeOSe/Ni foam catalyst was proposed as an excellent platform for water splitting to promote the oxygen evolution activity and stability. The advantages of this unique architecture are that the ultrathin and porous NiFeOSe nanowires can provide a huge number of exposed active sites, the highly-conductive Ni foam can promote the transfer of electrons, and the three dimensional-networked structures can facilitate the diffusion and penetration of electrolyte. Electrochemical measurements reveal that binder-free NiFeOSe/Ni foam electrode exhibits very low OER overpotentials of 244 mV at a high current density of 50 mA cm−2, small Tafel slope of 37 mV dec−1, and exceptional long-term stability of electrolysis for over 24 h in 1 M KOH alkaline medium. The binder free NiFeOSe/Ni foam electrode also exhibits a promising candidate for charge storage applications. This work
provides a promising strategy to develop transition metal based oxy-selenide as electrocatalysts for large-scale water-splitting and charge storage applications.
From NiRh2O4 to RhNi Alloy: Preparation and Characterization of Nanofibers for Hydrogen Evolution in pH-Universal Media
Authors: Jin Dasol , Yu Areum , Kim M. H. , Lee Youngmi , Lee Chongmok 
Published: May 2020

Considering the growing attention to sustainable hydrogen production from water splitting, advanced materials for electrocatalytic water splitting are central to the area of renewable energy. Ideal water splitting catalysts should have not only low overpotential to produce hydrogen but also decent stability for a controlled period. While the previously reported water splitting catalysts have various compositions, the ones based on earth-abundant and non-precious metals are being studied extensively for hydrogen and oxygen production. However, noble metal oxides, in general, still exhibit superior electrocatalytic activity and enhanced stability under extreme environment compared with other cheap metals. Therefore, mixing non-precious transition metals (e.g. Ni, Co and Cu) with noble metals could be a possible strategy to utilize highly active but expensive noble metals providing economic feasibility.
Here we present the synthetic processes and physical/electrochemical characterization of single-phase NiRh2O4
nanofibers (NFs) and their reduced form, RhNi NFs. Those NFs are synthesized through electrospinning, a simple way to facilitate 1D nanostructure, and post-thermal annealing process with and without hydrogen atmosphere. Under a certain optimized condition, single-phase NiRh2O4
NFs and single-phase alloy RhNi NFs are synthesized without and with hydrogen atmosphere, respectively. To find the proper synthetic conditions, NFs are electrospun with varying the precursor mixing ratios and calcined at different temperatures. The morphology and compositions of NiRh2O4
NFs and RhNi NFs were characterized by a field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The crystalline structure of the prepared NFs are investigated through high-resolution X-ray diffraction (XRD). Electrochemical activities of NiRh2O4
NFs and RhNi NFs for hydrogen evolution reaction (HER) are studied with rotating disk electrode (RDE) voltammetry in N2-saturated 1.0 M NaOH, 1.0 M PBS and 1.0 M HClO4 aqueous solutions; and compared with those of pure metallic Rh, Ni counterparts in addition to commercial Pt/C. This work was financially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2019R1F1A1059969 for CL) and Basic Science Research Program through the NRF funded by the Ministry of Education (NRF-2018R1A6A1A03025340 for YL and KMH).
Dynamic Self-Optimization of Hierarchical Porous Ni-Based Compounds As Bi-Functional, Efficient Catalysts for Water Splitting
Authors: Jiang Tao , Liu Taikai , Ansar Syed-asif , Montavon Ghislain , Liao Hanlin 
Published: May 2020

Developing cost-effective, bi-functional electrocatalysts to efficiently convert intermittent typical renewable energy resources into hydrogen via water splitting is vital for realizing carbon-free energy cycle but remain challenges. Here, we report dynamically self-optimized (DSO) pre-electrocatalyst comprising NiAl framework covering defect-rich Ni crystallites for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline media. Core@shell Ni@NiO nanoparticles with lattice defects as the catalytically active phases are generated in situ on NiAl framework upon electrochemical DSO-HER, while Ni crystallites on NiAl framework in situ transform into wrinkled jamborite-(Ni(OH)2/NiOOH) hybrid nanosheets with severe lattice distortion that can mediate the OER efficiently upon electrochemical DSO-OER.
Under 1 M KOH aqueous electrolyte, the bi-functional DSO catalysts show an overpotential of 200 mV with Tafel slope 39 mV dec-1 and -33 mV with Tafel slope of 42 mV dec-1 for oxygen evolution reaction (OER) and HER at 10 mA cm-2. When assembled as the cathode and the anode in a single electrolyzer, the resulting Ni-based catalysts can give a superior overall water splitting output. Such a remarkable feature of the catalysts lies in the synergistic effect of the high intrinsic activity arising from the presence of complex lattice defects on the nanostructures of the active phases and the strikingly enhanced catalytic surface area together with the accelerated electron/ion transport associated with the hierarchical multi-porous architecture.
The material is seen to dynamically reform into different active interfacial species during DSO-HER and DSO-OER, where the pristine and activated catalysts are analyzed with XRD, SEM, Raman, XPS and TEM. The study shows that Ni-based compounds operate as effective bi-functional catalysts in alkaline water splitting, promising for integration into renewable technologies based electricity in alkaline water electrolyzers for sustainable production of hydrogen.
One-Pot Synthesis of Nitrogen-Doped Carbon Supported Mn-Co Nanoparticles for Hydrazine Oxidation
Authors: Balčiūnaitė Aldona , Budrytė Eivilė , Vaičiūnienė Jūratė , Niaura Gediminas , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus 
Published: May 2020

The nitrogen-doped carbon (N-doped C), that has a graphene-like structure, has been chosen as a support for the deposition of Mn-Co nanoparticles (Mn-CoNPs) using a rapid microwave heating method with the aim to use them as the anode material for direct hydrazine fuel cells (DHFCs). For comparison, the pure CoNPs/N-doped C and MnNPs/N-doped C catalysts have been synthesized under similar conditions. The structure, morphology and composition of the synthesized catalysts have been characterized using Transmission Electron Microscopy (TEM), Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The electrocatalytic activity of the prepared Mn-CoNPs/N-doped C, CoNPs/N-doped C and MnNPs/N-doped C catalysts for hydrazine oxidation has been evaluated using cyclic voltammetry and chrono-techniques. Cyclic voltammograms on the prepared catalysts have been recorded in a 0.05 M N2H4 + 1 M NaOH solution at a potential scan rate of 10 mV s–1.
It has been determined that the Mn-CoNPs/N-doped C, CoNPs/N-doped C and MnNPs/N-doped C catalysts show an enhanced electrocatalytic activity towards the oxidation of hydrazine in an alkaline medium. Moreover, the oxidation process of hydrazine on the Mn-CoNPs/N-doped C, CoNPs/N-doped C and MnNPs/N-doped C catalysts is controlled by the diffusion processes. The data on the oxidation of hydrazine on the N-doped C supported Mn-CoNPs, CoNPs and MnNPs under various conditions are compared and discussed.
Investigation of Ionic Liquid/Membrane Matrix for the Mid Temperature PEM Fuel Cell
Authors: Hou Hui , Giffin Jürgen , Korte Carsten 
Published: May 2020

Operating polymer electrolyte fuel cells (PEFC) >100 °C allows a significant simplification of the necessary peripheral devices. It allows operation without feed gas humidification—respectively no water recyclation—and a more efficient cooling system. For operation temperatures <80 °C, PEFCs with NAFION® membranes show excellent electrochemical performance. However, at higher temperatures sulfonated fluoropolymer membranes suffers from the drying effects at atmospheric operation which leads to a dramatic decrease of the proton conductivity. When using phosphoric acid (H3PO4) doped polybenzimidazole membranes (PBI), a PEFCs can be operated in the temperature range of 160–180 °C (HT-PEFC). Nevertheless, due to poisoning effects by H3PO4 and its anionic species on the redox catalyst platinum and a low solubility of oxygen in H3PO4, the ORR kinetics is rather sluggish and leads to an insufficient power density. Moreover, at temperatures <150 °C the proton conductivity is not sufficient.
Thus, there is need for new proton conducting membrane materials for operation temperatures of 100–120 °C, whose conductivity is not related to a high degree of water swelling. Proton conducting ionic liquids (PILs) exhibit a high proton conductivity, low volatility and high thermal stability, as well as a high electrochemical stability over a wide temperature range [1-3]. Thus, PILs are the promising candidates as non-aqueous proton conductors.

This experimental study is focused on high Brønsted-acidic sulfoalkylammonium type PILs as 2-sulfoethylmethylammonium triflate [MSEA][TfO], 2-sulfoethylmethylammonium hydrogen sulfate [MSEA][HSA], 3-sulfopropyldiethylammonium triflate [DESPA][TfO] and 3-sulfopropyldiethylammonium hydrogen sulfate [DESPA][HSA]. The physico-chemical properties of the neat PILs, i.e. ORR kinetic current density, oxygen solubility, oxygen diffusivity, electric conductivity and thermal stability, are measured at temperatures relevant for fuel cell operation. Commercial polyetheretherketone (PEEK) and PBI are chosen as host membrane materials to immobilize the PILs in a polymer matrix. The (total) electric conductivity and the thermal stability of the PIL-polymer systems are also evaluated.
The influences of the cations or anions on the PILs and the different immobilization methods of PILs in membrane are investigated. The results show that with different PIL/membrane combinations, significant differences in thermal stability, mechanical stability and electric conductivity are present.
Literature:
[1] Yasuda, T. and M. Watanabe, Protic ionic liquids: fuel cell applications. MRS Bull., 2013. 38(7): p.560-566.
[2] Noda, A., K. Hayamizu, and M. Watanabe, J. Phys. Chem. B, 2001 105(20): p. 4603-4610.
[3] Huang, X.-J., et al., J. Phys. Chem. B, 2009. 113(26): p. 8953-8959.
Imaging-Based Analysis for Porous Nickel Materials for Alkaline Water Electrolysis
Authors: Arlt Tobias , Evangelisti Camilla , Markötter Henning , Liebert Michael , Paulisch Melanie , Kardjilov Nikolay , Röntzsch Lars , Rauscher Thomas , Mohseninia Arezou , Boye Jan-Peter , Bergbreiter Christian , Kaczerowski Jürgen , Damm-Ruttensperger Marc , Herrera Raoult , Bächler Heike , Bernäcker Christian Immanuel , Jörissen Ludwig , Manke Ingo , Banhart John 
Published: May 2020

Electrolyzer cells are a way of converting and storing excess energy and releasing it again if needed. Beside Li-ion-based batteries, this technique would enable to overcome the intermittent day-dependent availability of electricity (like solar or wind power). The power density and the amount of raw materials needed for the assembly of such cells can be improved through optimized manufacturing processes, especially the sintering process of the electrodes. The sintering process is crucial for the overall performance of an electrolyzer cell. The electrical conductivity as well as the media distribution inside the pores during cell operation needs to be tuned. Hereby, nickel particles are sintered on a nickel substrate. Different substances such as binder and surfactant, are added to the Ni(OH)2 before the sintering process is started. Ni(OH)2 will be reduced to Ni, resulting in an additional Ni coating on the Ni substrate. Material densification, decrease of the porosity and active surface are the most relevant factors during this process. To meet all the requirements a well-balanced sintering process in mandatory. A sufficient electrical conductivity requires well detached particles, while an optimal media transport requires more and large pores. Both can be met by using nickel particles with a defined size distribution of the particle diameters, and a balanced sintering process which significantly affects the conductivity and pores sizes. Moreover, remaining oxidized Ni, which is not an electrochemically active material, decreases the active surface of the sintered material.
This study focuses on the two-phase flow system through newly developed porous nickel materials. Therefore, imaging techniques are combined with electronic measurements and simulations. To characterize these materials results were taken from focused Ion beam (FIB), synchrotron tomography and neutron radiography. Typical structures are coated meshes, foams or expanded metals. The structure of nickel particles was analyzed in 3D using machine learning algorithms for image segmentation. In-operando measurements were performed at the neutron source BER II at Helmholtz-Zentrum Berlin, Germany. Different electric loads and materials were tested in order to obtain additional information to the electronical measurements in terms of media distributions, see figure 1.
The authors gratefully thank the German Federal Ministry for Economic Affairs and Energy (BMWi, Project AEL3D, grant number 03ET6063B) for financial support.

Figure 1
Meso-Structured Polymer Electrolyte Fuel Cell Electrode
Authors: Komini Babu Siddharth , Wang Xiaojing , Pant Lalit M. , Mukundan Rangachary , Weber Adam Z. , Borup Rod L. , Spendelow Jacob S 
Published: May 2020

Increasing the utilization of Pt and Pt alloy catalysts in polymer electrolyte fuel cell cathodes is critical to improving the high power density operation, particularly at low Pt loadings. State of the art electrodes are fabricated in an ink deposition process that leads to uncontrolled electrode architecture with random aggregates of functional domains (catalyst, ionomer, and pore volume) (1). The randomness in the domains induces high tortuosity transport pathways for ions and fluids, which cause severe transport resistance during high current density operation. Thin ionomer films cause additional transport resistance and poisoning of the Pt catalyst, which becomes more significant at low Pt loadings. Reducing the amount of ionomer in the catalyst domain without affecting the ionic transport resistance is key to improving the utilization of the Pt and reducing the transport resistance at low Pt loading.
Rational design of the electrode structure with controlled low tortuous ionic transport pathways could improve performance. The introduction of the ionomer pathways could also enable reduction of the ionomer volume in the catalyst domain, reducing the transport resistance. Middelmen et al. proposed electrode structures consisting of aligned components in a low tortuosity configuration to improve performance (2). In this work, we present an alternative electrode structure based on a vertically aligned array of Nafion pillars in the cathode catalyst layer, as shown in Figure 1a. Figure 1b shows the SEM image of the Nafion pillars. Pt supported on carbon catalyst was deposited on the Nafion pillars to fabricate a meso-structured electrode. Nafion pillars provide high conductive and low tortuous pathways for protons, reducing the effective transport distance, and enabling reduction of the ionomer binder in the catalyst domain.

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos.

References

1. S. Litster and G. McLean, Journal of Power Sources, 130, 61 (2004).
2. E. Middelman, Improved PEM fuel cell electrodes by controlled self-assembly, in, p. 9 (2002).

Figure 1
Characterization of Ionomer Membranes with Confocal Raman Microscopy
Authors: Böhm Thomas , Moroni Riko , Mu'min Muhammad Solihul , Breitwieser Matthias , Vierrath Severin , Thiele Simon 
Published: May 2020

Ionomer membranes are crucial components of electrochemical energy systems such as fuel cells, electrolyzers, or redox-flow batteries. They need to meet demanding requirements for high-performance and long-term stable devices, and a targeted optimization of the membranes requires exact knowledge of parameters such as membrane thickness, ion exchange capacity, or water uptake. We employ confocal Raman microscopy as a tool for in-depth characterization of membranes that are used in proton exchange membrane fuel cells and water electrolyzers. Raman spectroscopy as a vibrational spectroscopy technique is well suited to characterize ionomer membranes, and the combination of Raman spectroscopy with a confocal microscope additionally adds spatial resolution to this chemical analysis. Confocal Raman microscopy is a valuable tool to complement classical characterization of ionomer membranes that provides a plethora of chemical information about the investigated specimen on a single-digit micron scale.
We present our latest results on application-relevant ionomer degradation and water management in membranes determined by confocal Raman microscopy. We found that a Nafion NR-211 membrane that was aged in an accelerated stress test in a fuel cell suffered from severe thinning and an anisotropic increase in its equivalent weight between the electrodes.1 Both are signs of chemical-mechanical degradation and were quantified with high spatial resolution using confocal Raman microscopy (Fig. 1A). Further, we used confocal Raman microscopy to characterize ionomer composite membranes. Composite membranes are a promising approach to optimize membrane properties by e.g. integrating mechanically stabilizing porous networks. We quantified the equivalent weight along the depth profile of a Nafion XL membrane, and also analyzed the influence of the reinforcement layer on water distribution within the hydrated membrane (Fig. 1B).2

Figure 1: Results of ionomer membrane characterization by Raman microscopy. A) Quantification of degradation of Nafion NR-211 in a fuel cell (open circuit voltage (OCV) hold as stress test). B) Through-plane Raman image of water distribution in a Nafion XL membrane.
1. T. Böhm, R. Moroni, M. Breitwieser, S. Thiele and S. Vierrath, J. Electrochem. Soc.,
166(7), F3044-F3051 (2019).
2. M. S. Mu’min, T. Böhm, R. Moroni, R. Zengerle, S. Thiele, S. Vierrath and M. Breitwieser, J. Memb. Sci.,
585, 126–135 (2019).

Figure 1