bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrospun Platinum Group Metal Free Catalyst Powder/Nafion/PEO Cathodes for Hydrogen/Air Fuel Cells
Authors: Yarar Kaplan Begüm , Kang Narae , Pintauro Peter N. , Zulevi Barr , Serov Alexey
Published: May 2020

In recent years, there has been considerable research on platimum-group-metal-free (PGM-free) catalysts as the cathode material for proton-exchange membrane (PEM) fuel cells [1]. Although the oxygen reduction activity of these type of catalysts is lower than Pt or Pt-based alloys, a higher loading of these inexpensive catalysts may be a good way to balance sluggish oxygen reduction kinetics. One serious draw back of all PGM-free catalysts is their poor durability in a fuel cell. Pintauro and coworkers have shown the the durability issue can be solved using a cathode binder of Nafion® and poly(vinylidene fluoride), but the fuel cell power output was low [2]. In the present study, PGM-free cathode fabrication and performance are presented using particle/polymer electrospinning. Nanofiber mat cathodes with a catalyst loading of 1.0, 2.0, and 3.0 mg/cm2 were prepared using an iron based Fe-N-C catalyst (Pajarito Powder, NPC-2000), Nafion ionomer and poly (ethylene oxide) (PEO) as a carrier polymer for elelctrospinning. An SEM of one catalyst/Nafion fiber is shown in Figure 1. After removing PEO from a fiber mat by soaking in hot water, the nanofiber-based cathodes were incorporated into H2/air fuel cell membrane-electrode assemblies (MEAs) and their performance (power output and durability) was compared to that of conventional sprayed-cathode MEAs (with neat Nafion binder). The effects of fiber composition, thickness and the choice of solvent for electrospinning on fuel cell performance were also examined. The maximum power density of a PGM-free nanofiber-cathode MEA, was found to be 252 mW/cm2 at 80°C for H2 and air at 2 atm backpressure.

References:

1) Thompson, S.T.; Papageorgopoulos, D. Nat Catal
2, 558-561 (2019).

2) Slack, J.; Halevi, B.; McCool, G.; Li, J.; Pavlicek, R.; Wycisk, R.; Mukerjee, S.; Pintauro P. ChemElectroChem
5, 1537–1542 (2018)

Figure 1
Studies of Conditioning Protocols for Polymer Electrolyte Membrane Fuel Cells
Authors: Balogun Emmanuel
Published: May 2020

For optimal performance, there is a need to condition the fuel cell when it is being used for the first time. This process of conditioning is referred to as initial conditioning, activation or break-in procedure. The goal behind the initial conditioning is to increase the performance of the fuel cell until it gets to its peak value for optimized operation. Although, the exact mechanism. During this conditioning process, the polymer membrane and the polymer in the catalyst layer network are hydrated; contaminants are removed from the catalyst, and the number of catalyst’s active sites increases, and finally, the fuel cells attain an optimized and stable performance at the end of this step. However, the whole process of conditioning is known to be very time consuming, with many state-of-the-art conditioning protocols taking in excess of tens of hours to attain peak performance. Thus, this further increases the operating cost of the PEMFC as considerable amount of gas is expended for this process.

In this report, a new conditioning protocol that entails a series of oxidative starving at the cathode is introduced to accelerate the conditioning process. Unlike prior conditioning protocol, this protocol focuses not just on the hydration of the membrane electrode assembly but on reclaiming dried and blocked catalyst sites on the cathode electrode. The performance after conditioning shows that this new protocol gives a 10% and 11% increase in output power in comparison with the standardized United States Department of Energy and European Union conditioning protocol. Also the new conditioning protocol was able to reach its peak performance in 30minutes in comparison to the United States Department of Energy and European Union conditioning protocol that takes over 5 hours and 11 hours respectively.
Enabling Efficient Water Splitting with Advanced Materials Designed for High pH Membrane Interface
Authors: Kendrick Ian , Gerhardt Michael R. , Rojas-Carbonell Santiago , Wang Lan , Weber Adam Z. , Yan Yushan , Mukerjee Sanjeev
Published: May 2020

This research focuses on durable, high-performance materials and interfaces for advanced water splitting, enabling a clear pathway for achieving <$2/KgH2 (on scale) via anion exchange membrane (AEM)-based electrolysis. We aim to advance this goal via an improved fundamental understanding of both hydrogen and oxygen evolution reactions (HER/OER) leading to platinum group metal (PGM)-free catalyst materials. Here, we use NiFeCo and NiMo as OER and HER catalysts, respectively, in a full alkaline electrolysis cell. A thermally stable, multi-cation AEM is used to operate the cell at elevated temperatures thereby lowering the operating potential by increasing the kinetics of the respective catalytic reactions. The transition metal catalysts, paired with this novel AEM, have been used to achieve an operating potential of 1.79 V at 1 A/cm2. This potential is 300 mV lower than similar electrolysis cells equipped with PGM-based catalysts. We have also demonstrated the efficacy of the less caustic potassium carbonate solution as a replacement for potassium hydroxide as an electrolyte. By using a carbonate-based electrolyte, the hydroxide ion required for the anodic reaction is continuously replenished by re-establishing an equilibrium with water. This consideration, coupled with the reduced alkalinity of the carbonate solution, yields an electrolysis cell capable of sustained operation with minimal increase in operating potential.
Tantalum Carbide Supported Iridium Based Oxygen Evolution Reaction Electrocatalysts for Polymer Electrolyte Membrane Water Electrolysis
Authors: Rezaei Nafiseh , Peppley Brant A
Published: May 2020

In this study, the effect of ball milled tantalum carbide (TaC) as a support on performance of an Iridium (Ir) based catalyst for polymer membrane water electrolyzers (PEMWE)s is assessed. Supported and un-supported Ir-based catalysts were synthesized via a surfactant-mediated method at room temperature. The synthesized catalysts were analyzed using physical and chemical characterization methods including nitrogen physisorption analysis, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), SEM/wavelength dispersive spectroscopy (WDS), transmission electron microscopy (TEM)/ scanning transmission electron microscopy (STEM) and X-Ray photoelectron spectroscopy (XPS). It was observed that due to less agglomeration and better dispersion of supported catalyst on TaC, BET surface area of the supported catalyst was 25 times larger than the unsupported one. XPS results also indicated the oxidation state of Ir in synthesized catalysts is a mixture of Ir0, Ir+3 and Ir+4. Based on EDS and XPS results, it was concluded that the synthesized catalyst is a mixture of metallic iridium and iridium oxide (Ir-IrOx). Electrochemical properties of the synthesized catalysts were also studied using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) in a 3-electrode system. The supported catalyst shows three times the voltammetric charge compared to the unsupported catalyst. Based on the LSV measurements, the mass activity of the supported catalyst had a 10-fold increase in comparison with that of the unsupported one. Ir-based catalyst synthesized via the surfactant-mediated method and supported on ball milled TaC showed the best performance.
(Invited) Surface Decorated Pt-Based Nanocrystals for Hydrogen Evolution Reaction in Alkaline Media
Authors: Choi Sang-Il
Published: May 2020

Hydrogen evolution reaction (HER) in alkaline media consumes massive electrical energy during water electrolysis owing to the sluggish reaction kinetics. Thus, the development of HER electrocatalysts remains a great challenge. Recent advances in nanocatalysts offer opportunities to enhance electrochemical reactions. In this presentation, we introduce control of catalytic surface conditions such as facet, composition, and morphology in the case of Pt-based nanocatalysts. First, we introduce an effective electrocatalyst based on Pt nanocrystals where Ni(OH)2 is formed on the surface during synthesis. The prepared bimodal Pt-Ni(OH)2 electrocatalysts exhibit improved HER activity. Then, we show Pd@Pt and PdH@Pt core-shell nanocrystals as model catalysts to understand the ligand and strain effects toward alkaline HER.
(Invited) Solar Photoelectrochemical Fuel Generation Using Electrochemically Fabricated Nanomaterials
Authors: Varghese Oomman K
Published: May 2020

Replacing fossil fuels with chemical fuels generated from carbon free resources or via carbon dioxide recycling using solar energy has been widely recognized as a potential strategy for controlling the accumulation of carbon dioxide in the atmosphere and bringing sustainable developments in the energy sector. Among the solar fuel production technologies evolved in recent decades, water splitting and carbon dioxide reduction performed using solar photoelectrochemical (PEC) processes are highly promising. The PEC processes utilize photocatalytic properties of semiconducting materials for the conversion of energy in the ultraviolet to near infrared region of the solar spectrum to chemical energy. Since the development of electrochemical methods to fabricate highly ordered nanostructured semiconductors, there has been a surge of activity in involving these materials for PEC fuel generation. Electrochemical processes such as anodic oxidation have been demonstrated to yield stable materials with superior light harvesting and utilization properties. An area of substantial research interest in recent years is the fabrication of new materials with improved PEC performance using a combination of techniques including electrochemical. Such hybrid techniques have introduced several low dimensional materials and heterostructures with unique properties. This presentation is aimed at discussing the recent advances in PEC fuel generation processes brought by the nanomaterials and heterostructures fabricated using electrochemical and hybrid techniques.
Investigation of the Photocorrosion of n-Gap Photoanodes in Acid with in-Situ UV-Vis Spectroscopy
Authors: Spurgeon Joshua M. , Pishgar Sahar , Strain Jacob , Gulati Saumya , Sumanasekera Gamini , Gupta Gautam
Published: May 2020

Semiconductors of the III-V class are among the most promising materials for high efficiency solar fuels applications, particularly in tandem devices. Unfortunately, these materials are known to undergo oxidative corrosion as photoanodes in strongly acidic or alkaline electrolyte. In striving to overcome this challenge, researchers need to understand the fundamental degradation behavior during photoelectrochemical operation. Studying the in-situ photocorrosion process has largely been limited thus far to expensive and labor-intensive techniques that are not widely available in most labs. Herein, the corrosion of n-GaP, a promising III-V material for tandem top subcells, was investigated in strongly acidic electrolyte using an in-situ UV-Vis spectroscopy technique to monitor dissolved Ga and P species as a function of applied bias and time. The changing faradaic efficiency of the electrochemical GaP oxidation reaction was calculated from this data and used to interpret the corrosion process in conjunction with SEM and XPS characterization. Most notably, p+-GaP and n-GaP displayed strikingly different corrosion behavior, with p+-GaP dissolving uniformly across the active area and the corrosion faradaic efficiency increasing to a steady value. Illuminated n-GaP, in contrast, showed initially high corrosion faradaic efficiency which decreased during operation and was attributed to the phenomena of anisotropic surface etching and micropore formation during the beginning stages of photoanodic operation. In addition, corrosion measurements were made with thin conformal coatings of TiO2 as a protective barrier layer on the GaP surface. Although the protective coating slowed the rate of GaP dissolution, the TiO2 layers produced herein contributed significant charge-transfer resistance and still showed similar trends in the corrosion faradaic efficiency vs. time as the bare n-GaP.
(Invited) SECM and Photo-SECM on TEM Grids: Toward Correlated Electrochemical/TEM Imaging of Catalysts
Authors: Mirkin Michael V. , Sarkar Sujoy , Wang Xiang , Bae Je Hyun
Published: May 2020

Understanding and improving the properties of photocatalysts and electrocatalysts can have important implications for energy conversion and storage. Studying heterogeneous catalysts is challenging because their activity depends strongly on local atomic structures. Therefore, probing electrocatalytic reactions at specific local sites is critically important. By correlating the scanning electrochemical microscopy (SECM) data with atomic scale structural and bonding information obtained by transmission electron microscopy (TEM) techniques with one-to-one correspondence, one can elucidate the nature of the active sites. To enable multi-technique imaging of the same nanoscale portion of the catalytic surface, we are developing methodology for using a TEM finder grid as a substrate in SECM experiments. In this paper, we present the results of first nanoscale SECM and photo-SECM experiments on carbon TEM grids, including imaging of semiconductor nanorods.
(Invited) Surface Functionalized Copper-Cobalt Oxide Nanostructures for Efficient Water Splitting
Authors: Nath Narayan Chandra Deb , Park Hyunwoong , Lee Jae-Joon
Published: May 2020

The low-cost and low-toxic copper-cobalt oxide, CuCo2O4 have attracted a great deal of research interest owing to their wide range of applications such as oxygen evolution reaction, oxygen reduction reaction, hydrogen evolution reaction, alcohols oxidation, H2O2 decomposition, urea oxidation, and energy storage. Their controllable composition, electronic structure, valence states or redox characteristics, morphology, and high catalytic property have made them suitable as universal catalysts. However, their low intrinsic electrical conductivity still overshadows their practical application to some degree. In addition, The conventional preparation procedures of copper-cobalt oxide result in relatively low catalytic activity or large OER overpotential for catalytic reactions. In the present report, we have grown a series of surface functionalized Cu
x
Co3

-

x
O4 nanostructures directly on a charge-collecting substrate (e.g., Ni Foam) using a straightforward electrochemical deposition process and investigated the effects of its surface functionalization, morphology, content of oxygen vacancies, electrochemically active surface area (ECSA), and electrical conductivity on the performance of water splitting.

Figure 1
(Invited) Photoelectrochemical Solar Fuel Production Using Organic Semiconductors
Authors: Sivula Kevin
Published: May 2020

Pi-conjugated carbon-based semiconductors are well-established as high-performance and easily-processed materials for inexpensive and scalable solar energy conversion in organic photovoltaic (OPV) devices, but their promise in the economic conversion of solar energy into chemical energy (solar fuels) has only recently been recognized. In this presentation, I will discuss the main approaches for employing organic semiconductor-based devices towards solar H2 generation via water splitting and review the state-of-the-art.[1] OPV-biased water electrolysis has advanced significantly, now exceeding 6% solar-to-hydrogen conversion efficiency. However, the direct water splitting by an organic semiconductor in a photoelectrochemical cell, which has attractive advantages, remains limited by the intrinsic stability of organic semiconductors when placed in direct junction with aqueous electrolyte. I will further present experimental insights into the operational stability of donor:acceptor bulk heterojunction photocathodes and photoanodes[2] with an organic/water interface. Using sacrificial redox couples and various electrochemical analysis including impedance spectroscopy we identify and quantify the key factors that govern long-term photoactivity (>12 h). These insights can be extended to overall water splitting with appropriate catalyst overlayer design. Overall our advances with organic semiconductor photoelectrodes open a new path for economically feasible solar fuel production.

[1] L. Yao, A. Rahmanudin, N. Guijarro, K. Sivula, Adv. Energy Mater.
2018, 1802585.

[2] P. Bornoz, M. S. Prévot, X. Yu, N. Guijarro, K. Sivula, J. Am. Chem. Soc.
2015, 137, 15338.
(Invited) Insights on Scale-up of BiVO4-Based Photoelectrochemical Water Splitting Devices
Authors: van de Krol Roel , Abdi Fatwa Firdaus
Published: May 2020

With the STH efficiencies of metal oxide-based PV-PEC water splitting devices now approaching 10%, the next step is to move beyond laboratory experiments and demonstrate large area devices. We demonstrate an unbiased 50 cm2 PV-PEC water splitting device with an STH efficiency of 2.1%. While this is the highest reported value for a large-area BiVO4-based water splitting device, it is still a factor of ~3 below the 6.3% efficiency we achieve for the corresponding small-area device [1]. This illustrates that straightforward scale-up of spray-deposited BiVO4 photoanodes from <1 to 50 cm2 leads to significant efficiency losses. We studied the influences of variation in materials quality over larger areas, substrate conductivity, electrolyte conductivity, and cell geometry. At relatively modest photocurrent densities (2 - 3 mA/cm2), the total voltage losses amount to ca. 600 mV for our 50 cm2 device. The ohmic losses in the transparent conducting substrate (F-doped SnO2) represent only ~10% of the total losses. A much larger loss mechanism is due to mass transport limitations of the ionic species in the electrolyte. Specifically, we show that lateral diffusion in the direction parallel to the electrode surface plays a more important role that one would intuitively expect. We further quantified the different loss mechanisms using a combination of finite element analysis modeling (COMSOL Multiphysics®) and in-situ quantitative analysis of the fluid dynamics and pH of the electrolyte using particle image velocimetry and fluorescence techniques (Figure 1). This feedback mechanism between simulation and experiment allows a more accurate model construction and validation. Based on these insights, electrochemical engineering strategies to overcome the losses associated with scale-up are offered, which would limit the voltage loss for large-area devices to less than 50 mV.

References:

[1] I.Y. Ahmet, Y. Ma, J.W. Jang, T. Henschel, B. Stannowski, T. Lopes, A. Vilanova, A. Mendes, F.F. Abdi, R. van de Krol, “Demonstration of a 50 cm2 BiVO4 Tandem Photoelectrochemical-Photovoltaic Water Splitting Device”, Sust. Energy Fuels 3, 2366-2379 (2019).

Figure 1
CO2 Electroreduction to C2 / C2+ Products Using Membrane Electrode Assembly
Authors: Nabil Shariful Kibria , Kibria Md Golam
Published: May 2020

Considering the global average, 2018 experienced the highest concentration of CO2 in atmosphere (approximately 407 ppm). Although several policies and regulations are in action, annual CO2 in atmosphere is still on the rise for past decades. As an outcome, anthropogenic CO2 generation and subsequent atmospheric emission are key issues under global sustainability challenges. Moreover, this CO2 is also related to other irreversible effects which are climate change, ozone layer and fossil fuel depletion. Consequently, tons of researches involving significant CO2 reduction and conversion to assets are on the track. Currently, research efforts on electrochemical reduction of CO2 using alkaline flow cell configuration is at the forefront for its compact and flexible nature without the need of ancillary equipment. In this configuration, alkaline electrolyte, catalyst and the diffused CO2 establish a three-phase reaction interface enabling highly selective electroreduction of CO2 to various C2/C2+ fuels and chemical feedstocks. However, there are some major challenges associated with this configuration, including low CO2 conversion efficiency due to carbonate salt formation, catalyst poisoning due to impurity deposition, and electrode flooding. In this work, we have studied a robust cell configuration i.e., zero-gap membrane electrode assembly (MEA), wherein cathode and anode are separated by solid polymer electrolyte (ion-exchange membrane). Here cell operation and reaction kinetics are similar to liquid phase flow cell except exclusion of catholyte. Recent studies have revealed that removal of catholyte certainly overcomes the aforesaid limitations of liquid phase flow cell. In this context, here, we utilized a zero-gap gas-phase electrolyzer (MEA) for electrochemical CO2 reduction to multi-carbon products, including ethylene and ethanol. Instead of traditional carbon-based gas diffusion electrode (GDE), here, we utilized porous PTFE based GDE for stable CO2 reduction reaction. Copper nanoparticles, sputter coated on porous PTFE sheet, anion exchange membrane (AEM) and nickel foam (i.e., anode) are used to develop the MEA. A 5 cm2 stainless steel electrolyzer (MEA) was used for this study. Preliminary results show a faradaic efficiency for C2H4 (~55%) at current density (~50 mA/cm2) at -2.5 V vs Ag/AgCl with 5 M KOH as anolyte. We will report on the effect of catalyst modification, membrane, reaction environment including effect of humidity, CO2 flowrate and anolyte on the overall cell performance i.e., energy efficiency and CO2 conversion efficiency.

Keywords:
CO2 Electroreduction, Renewable Fuels, Membrane Electrode Assembly, Current Density, Faradaic Efficiency
(Invited) Efficient CO Production from CO2 and H2o By the Aid of Artificial Photosynthesis
Authors: Teramura Kentaro
Published: May 2020

The reduction in human-induced emissions of CO2 from automobiles, factories, power stations etc., over the next 15 years is currently one of the most important issues facing the planet. We should therefore attempt to develop industrial processes using CO2 as a feedstock to build a sustainable society. Linear CO2 molecules adsorbed on the surface of the solid bases are converted into unique structures, such as bicarbonate and carbonate species possessing lattice oxygen atoms. We believe that the process involves the capture and distortion of CO2 upon adsorption on a solid base through activation by photoirradiation. These days, we succeeded in designing highly selective photocatalytic conversion of CO2 by H2O as the electron donor, by the simultaneous use of an inhibitor of the production of H2 and a material for CO2 capture and storage. An isotope experiment using 13CO2 and mass spectrometry clarified that the carbon source of the evolved CO is not the residual carbon species, but the CO2 introduced in the gas phase. In addition, stoichiometric amounts of O2 were generated together with CO.
(Invited) Highly Selective and Efficient Conversion of CO2 to Fomate at 100 mA/cm2
Authors: Shin Woonsup
Published: May 2020

We succeeded in fabricating a dental amalgam composition on a copper foam electrode and could convert CO2 selectively to formate. The formate was produced at a current efficiency of 80~100% in the wide range of the potential shown below. The remaining electricity was used only for producing H2. The concentration of the produced formate is over 1.2 M in the batch electrolysis of 30 hours operation. The CO2-to-formate conversion system built based on the electrode in 9 cm x 9 dimension is shown to be stable in continuous operation at 100 mA/cm2 for more than a month.

Figure 1
(Invited) Virtual Analysis of Gas-Diffusion-Electrode CO2 Electrolyzers
Authors: Weng Lien-Chun , Bui Justin C. , Romiluyi Oyinkansola , Bell Alexis T. , Weber Adam Z.
Published: May 2020

The electrochemical reduction of CO2 (CO2R) to value-added products is an attractive technology for tackling the rising atmospheric CO2 levels and storing intermittent renewable energy into chemical bonds. Fundamental understanding of CO2R has progressed significantly in recent years and is critical in the development of CO2R to liquid-fuel electrolyzers, where gas-diffusion electrodes (GDEs) have been shown to be key enabling architectures. Various designs have been proposed and studied in the literature to enhance overall selectivity, rates, and maximize the conversion of CO2, the latter of which is only now being recognized as a critical issue. In this respect, there is a need to explore the governing phenomena inherent in these architectures to enable optimization. Mathematical modeling is ideally suited to tackle and explore these multiphysics interactions and provide virtual design analysis.

In this talk, we discuss modeling methodologies and physics inherent in these devices and present our recent modeling of GDEs for CO2 reduction. We specifically examine the impacts of multiphase flow and related phenomena on overall cell performance. We then explore the performance and limitations of various cell designs guided by simulation results and examine potential methods for improving water management and tuning catalyst selectivity including the use of different anion-exchange and bipolar membranes. Finally, we discuss the disparities in local environments between aqueous and GDE devices and propose strategies to reduce the gap in knowledge between the two systems.

Acknowledgements

This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.
Probing the Boundary Layer of Electrochemical CO2 Reduction with Electrochemical Mass Spectroscopy
Authors: Tackett Brian M. , Moffat Thomas P
Published: May 2020

Research into the aqueous electrochemical reduction of CO2 to fuels and commodity chemicals has grown quickly in conjunction with increasing concerns of greenhouse gas emissions and wider availability of “clean” electrons coming from solar and wind power. Reduction of CO2 to valuable multi-carbon products, such as ethylene or ethanol, has been observed on copper-based electrocatalysts, but many fundamental questions remain about such processes. Specifically, the nature of the active site under reaction conditions is unclear, due to possibilities for surface copper rearrangement,1 subsurface reactant species,2,3 and changes in local pH,4 among others. Here we attempt to deconvolute these process to gain a more fundamental understanding of this electrocatalytic reaction. We utilize a newly designed thin layer electrochemical mass spectrometer with 100% collection efficiency at fast time-scales5,6 to probe the product species in the boundary layer during electrochemical reduction of CO2 on copper-based electrocatalysts. We employ a range of electrode sizes to enable product sensitivity at low overpotentials and at high current densities. We combine these measurements with an analysis of pH at the surface to better understand the local pH changes as a function of reaction potential. These insights into boundary layer phenomena should guide future design of both selective catalysts and efficient device configuration for CO2 electroreduction.

References

1. C. M. Gunathunge et al., J. Phys. Chem. C, 121, 12337–12344 (2017) https://pubs.acs.org/doi/10.1021/acs.jpcc.7b03910.

2. M. Favaro, H. Xiao, T. Cheng, W. A. Goddard, and E. J. Crumlin, Proc. Natl. Acad. Sci. U. S. A., 114, 6706–6711 (2017).

3. T. M. T. Huynh and P. Broekmann, ChemElectroChem, 1, 1271–1274 (2014) http://doi.wiley.com/10.1002/celc.201402147.

4. N. Gupta, M. Gattrell, and B. MacDougall, J. Appl. Electrochem., 36, 161–172 (2006) https://doi.org/10.1007/s10800-005-9058-y.

5. D. B. Trimarco et al., Electrochim. Acta, 268, 520–530 (2018) https://www.sciencedirect.com/science/article/pii/S0013468618303438.

6. D. B. Trimarco, T. Pedersen, O. Hansen, I. Chorkendorff, and P. C. K. Vesborg, Rev. Sci. Instrum., 86, 075006 (2015) http://aip.scitation.org/doi/10.1063/1.4923453.
Fully Blossomed WO3/BiVO4 Structure Obtained Via Patterned Fto for Highly Efficient Water Splitting
Authors: Ju Sucheol , Lee Heon
Published: May 2020

Photoelectrochemical (PEC) water splitting is an eco-friendly energy generation process that gives rise to a hydrogen source as a result of the redox reaction of water, using the energy of absorbed light. Because of the process involved, the overall efficiency is expressed as a product of the light absorption efficiency (ηabs), the charge separation efficiency (ηsep) and the charge transfer efficiency (ηtrans). PEC water splitting is difficult to commercialize because of its low efficiency and difficulty in applying to a large area. In order to alleviate these problems, considerable amount of research has gone into pattern to increase the efficiency of PEC itself and on the PEC-PSC tandem cell, which is the combination of a perovskite solar cell and PEC. However, until now, studies on applying pattern engineering to PEC have been restricted to the use of Au or Pt as electrodes. In this case, despite of gaining the advantage of the effect of pattern, it also has the disadvantages of being unsuitable of PEC-PSC tandem cell (due to the opacity of Au and Pt) and being impractical for application to the field of energy research (due to Au and Pt being very expensive).

In the work presented in the submitted manuscript, we have studied the increase in PEC efficiency by forming a patterned FTO. The patterned FTO, formed by direct printing, is transparent and cheaper than Au and Pt, making it a suitable electrode for applications in energy research as well as in a PEC-PSC tandem cell. It also has the desired effect of pattern. In the case of Au or Pt electrode, hydrothermal synthesis is of limited use as Au and Pt are detached due to the oxidation of Cr used as an adhesion layer. However, due to the high stability of FTO, hydrothermal synthesis is possible in our case.

we fabricated a flat Fluorine-doped SnO2 (FTO) electrode and a micro cone structured FTO electrode. We then fabricated a WO3 nanoflakes (NF)/BiVO4 photoanode on top of each of these two types of FTOs. The photocurrent density of WO3/BiVO4 on micro cone patterned FTO reached 1.50 mA/cm2 at 1.23 VRHE, which is 34 % higher than the that of WO3/BiVO4 on flat FTO(1.12 mA/cm2). When measured with 0.5 M Na2SO3, the photocurrent densities of FB-WO3/BiVO4 and B-WO3/BiVO4 were found to be 2.48 and 1.80 mA/cm2, respectively, at 1.23 VRHE. These results show the same trend as the (J – V) curve.

Our study was successful in increasing PEC efficiency by patterning transparent and cheap electrode materials (FTO), suitable for applications in PEC-PSC tandem cells, using direct printing. The significant advance demonstrated here indicates that it is possible to fabricate high efficiency PEC-PSC tandem cell using the FTO architecture, and to facilitate large-area PEC commercialization by using processes suitable for large-scale productions (namely direct printing, spray pyrolysis, and hydrothermal reaction).

Figure 1
(Invited) Bioinspired Design: Hybrid Nifeooh/α-Fe2O3/Graphene Photoelectrodes with Advanced Water Oxidation Performance
Authors: Janáky Csaba , Kormanyos Attila
Published: May 2020

In this talk, I am going to present how electrodeposition allows the synthesis of complex photoelectrode architectures with precisely controlled structure and composition. The presented photoelectrode assembly follows a bioinspired design, where the different components have different function. Fe2O3 was responsible for light absorption, the graphene (GR) framework ensured proper charge transport, while the FeNiOOH overlayer allowed facile water oxidation kinetics. Photocurrent densities were notably higher compared to the respective single- and two-component counterparts. However, introducing a carbon component to a photoanode raised an additional concern, namely that photogenerated holes can oxidize the underlying nanocarbon framework. By adding a third component to the system (i.e., a FeNiOOH overlayer), we were able to suppress the corrosion of the nanocarbon matrix, while all the benefits gained by the presence of GR were still present. When graphene nanoflakes are present, two additional processes occur: better transport of photogenerated electrons towards the back contact, due to the highly conductive nature of graphene and some of the photogenerated holes can also be transported to graphene and oxidize it (note the metallic nature of graphene). Finally, if the surface of hematite is decorated with a co-catalyst, which passivates the surface states, holes are rapidly transported to the co-catalyst and to the substrate. Most importantly, because of the rapid hole-transfer to the co-catalyst, the pathway leading to the corrosion of graphene is successfully eliminated.
Monolithic Wireless Photoelectrochemical Device Design for Efficient Water Splitting Applied to Amorphous Silicon and III-V Photovoltaic Material
Authors: Koonce Jonathan G , Cheng Wei , Lee Joun , Rassoolkhani Alan , McKee Austin , Mubeen Syed
Published: May 2020

Considerable research has been done by many groups for the creation of a standalone and integrated photoelectrochemical water splitting device that generates hydrogen using only energy from the sun. However, there remains significant challenges for improving the efficiency and long-term stability of such devices. Many hydrogen and oxygen evolving catalysts are active in concentrated acidic or basic electrolyte which necessitates schemes for protecting the photovoltaic material of choice from chemical and electrochemical corrosion. It is also necessary to optimize catalyst activity and loading for best solar-to-hydrogen efficiency.

Here we demonstrate a device structure applied to both a triple-junction amorphous silicon solar cell as well as a triple-junction III-V gallium arsenide solar cell. This design demonstrates efficient and stable water splitting which can be applied to any existing photovoltaic material. The triple-junction silicon device demonstrates application to cheap, commercially available solar cells. Devices made from these solar cells are anodic on the light absorbing side – which often suffer from accelerated decomposition due to corrosion from undesired photo-oxidation on the device surface. Similarly, the triple-junction gallium arsenide device demonstrates the application of this device structure to a high efficiency PV cell with opposite charge carrier orientation (cathodic reaction on light absorbing side of the device).

This design decouples the protective coating from the integrated catalysts, which allows the optimization of the transparent protective coating in the corrosive electrolyte to be tuned separately from the activity of the OER or HER catalysts. Our most efficient device shows over 10% solar-to-hydrogen efficiency and our best stability shows over 100 hours of operation.
Asymmetric Strain in the Oxidized and Reduced States of Heterogeneous Electrocatalysts
Authors: Smith Rodney D. L.
Published: May 2020

The growing number of functional examples of “strain engineering” is drawing attention to the influence that mechanical or geometric considerations can have on the electronic structure and electrochemical behavior of electrocatalysts. It will be shown that the concept of lattice strain, and the changes in electronic structure that accompany it, can explain the experimentally observed trends in electrochemical behavior of common mixed-metal oxide catalysts for the oxygen evolution reaction. Structural analysis of a series of iron-nickel hydroxide materials reveal a significant change in O-Ni-O bond angles upon electrochemical oxidation.1 Subsequent analysis shows that insertion of ions with varied ionic radii into a Ni(OH)x host lattice introduces localized geometric distortions in the nickel environments that can be observed by tracking Ni-based d-d transitions in the near-infrared.2 The type (tensile or compressive) and magnitude of strain is correlated to the oxidation state of nickel ions and the ionic radius of the secondary ion. Experimentally observed trends in electrochemical behavior track the ionic radius of the secondary ion, indicating that the degree of strain directly correlates to electrochemical behavior. Density functional theory calculations indicate that inequivalence of this internalized strain in the oxidized and reduced states of the catalyst material introduces asymmetry into the potential energy surface landscape. This asymmetry effectively decreases the activation energy for electron transfer and may simultaneously decrease the electrochemical transfer coefficient. Evidence suggests that the synthetic protocol employed exerts significant influence over the placement of secondary ions and ability to observe this effect.3

(1) Smith, R. D. L.; Pasquini, C.; Loos, S.; Chernev, P.; Klingan, K.; Kubella, P.; Mohammadi, M. R.; González-Flores, D.; Dau, H. Energy Environ. Sci
2018, 11, 2476–2485.

(2) Alsac, E. P.; Whittingham, A.; Liu, Y.; Smith, R. D. L. Chem. Mater.
2019, 31, 7522–7530.

(3) Rong, W.; Stepan, S.; Smith, R. D. L. MRS Adv.
2019, 4, 1843–1850.
The Interfacial Nature of Mechano-Chemo-Electrical Potential and Its Application to Processing and Failure Prediction in Solid State Lithium Ion Batteries
Authors: Raj Rishi
Published: May 2020

The incorporation of mechanical stresses into descriptions of the electrochemical potential is of fundamental significance in understanding the processing and failure mechanisms in solid state lithium ion batteries. The chemical potential is defined by (i) the nature of the species, e.g. lithium atoms, or ions, and (ii) by the site or the phase where the species reside. The second point draws a distinction between the influence of mechanical tractions applied to a surface or an interface – e.g. grain boundaries – and the volumetric strain energy obtained from solutions to the usual boundary value problems in mechanics. This distinction is great, and not sufficiently recognized in the literature. In this presentation the interfacial mechano-chemo-electrical potential will be described and then applied to three problems in the processing and failure prediction of solid state lithium ion batteries made with Li-metal anodes.
Interfacial Properties of Bilayer SOFC Electrolytes Via Scale Bridging Simulations
Authors: Ghuman Kulbir Kaur , Gilardi Elisa , Pergolesi Daniele , Staykov Aleksandar , Kilner John A. , Lippert Thomas
Published: May 2020

There has been significant interest in the bilayer materials used as Solid Oxide Fuel Cell Oxides (SOFCs) electrolytes. Multiple studies have explored the two participating materials in bilayer electrolytes, individually. However, the interfaces formed by them remain largely unexplored due to their complex nature. In order to advance the fundamental science of bilayer electrolytes, in this work a multiscale modeling study of the interface formed in commonly used SOFC electrolyte- ‘Ceria (CeO2)/yttria-stabilized zirconia (YSZ)’, was conducted. First, a realistic YSZ/CeO2 interface model containing all the important microstructural features of the interface such as dislocations, point defects, and lattice strains was prepared by using classical molecular dynamics (MD) simulations. Then, density functional theory was implemented to analyze the electronic properties of the realistic YSZ/CeO2 interface model prepared by MD. It was found that, at the interface, the overall strain in CeO2 and YSZ is compressive and tensile, respectively, as expected; however, the local strain at the core of the dislocation is converse. At dislocations, CeO2 was found to have tensile strain whereas YSZ has compressive strain. The presence of tensile strain in CeO2 at the core of the dislocations might contribute to the formation of O vacancies and reduction of Ce4+ to Ce3+, as observed in experiments. Overall, this work for the first time integrates the classical and quantum simulations to prepare and analyze a realistic working-class YSZ/CeO2 interface, resulting in the long-sought explanation for the experimentally observed Ce reduction at the YSZ/CeO2 interface.1

Acknowledgments

This work was supported in part by the International Institute for Carbon-Neutral Energy Research (I2CNER) sponsored by the World Premier International Research Center Initiative (WPI) and the JSPS Core-to-Core Program, A. Advanced Research Networks and Paul Scherrer Institut. The computations were performed by using Computational Science Research Center, Okazaki, Japan, and the HPC supercomputers at I2CNER, Kyushu University, Japan.

References

[1] Kulbir K. Ghuman, Elisa Gilardi, Daniele Pergolesi, Aleksandar Staykov, John Kilner, Thomas Lippert, Microstructural and Electronic Properties of YSZ/CeO2 Interface via Multiscale Modelling
, Acta Materialia (2019) Submitted.
(Invited) Modeling Electrolyzers: Exploring the Applied Voltage Breakdown
Authors: Weber Adam Z.
Published: May 2020

To commercialize successfully polymer-electrolyte electrolyzers and optimize their performance, one requires a detailed understanding of the underlying physics and phenomena. Mathematical modeling is ideally suited to explore such intricacies. In this Tutorial, the modeling equations and approaches towards both proton- and hydroxide-conducting polymer electrolyzers will be detailed. This includes the introduction of the applied voltage breakdown that separates the overall polarization curve into its constitutive parts such that the limiting mechanisms can be ascertained. Throughout, different case studies will be explored including impacts of bubble generation, liquid versus vapor feed, and pH changes due to carbonate and hydroxide solution feeds. A key focus of the Tutorial will be in exploring and describing the various transport and competing phenomena within the electrolyzer cell.

Acknowledgements

This work was funded under the HydroGen – AWSM Consortium funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy.
Electron Transfer-Catalyzed Vinylcyclopropane Rearrangements
Authors: Okada Yohei , Maeta Naoya , Kamiya Hidehiro
Published: May 2020

Recently, electron has been recognized as the simplest catalyst in the field of synthetic organic chemistry. Addition or removal of electron can activate small molecules for further chemical transformations, which is referred to as redox catalysis. Reductive and/or oxidative single electron transfer (SET) can be induced by means of electro- and photochemistry, where an electron can play a role of catalysts. Radical ions are primarily generated via SET, offering unique reactive intermediates.

Distonic radical ions are transient species with formally separated radical and charge cites. They potentially exhibit radical and ion reactivities independently, which may differ from usual radical ions. However, distonic radical ions are not commonly used as reactive intermediates in the field of synthetic organic chemistry, probably because of lack of their simple generation methods.

We have been developing oxidative SET-triggered cycloadditions in a lithium perchlorate/nitromethane solution. Radical cations are involved in the reactions as distinctive reactive intermediates, facilitating intermolecular carbon-carbon bond formations. We questioned whether the distonic radical cation can also be generated by oxidative SET, leading to novel chemical transformations. In this presentation, oxidative SET-catalyzed vinylcyclopopane rearrangements will be described.

Figure 1
Scanning Electrochemical Probe Microscopy for Corrosion-Fatigue Manipulation
Authors: Yassine Sarah
Published: May 2020

Corrosion-fatigue is used to describe the weakening of the material resulting from the cyclic loading in a corrosive environment. Understanding this phenomenon reflects on a wide range of electrochemical applications such as hydraulic turbines and gives a better influence on the microstructure defect which by far isn’t clear yet. The ability to investigate the corrosion-fatigue at its point of initiation with a high spatial resolution is believed to manipulate and limit its occurrence on metal surfaces. However, conventional methodologies used are limited to average-base electrochemical studies leaving it insufficient for single-point measurements. Scanning electrochemical probe microscopy, for instance, allows us to map and characterize the corrosion behavior of different metals including its cracking initiation and propagation, at the micro-scale while maintaining a high resolution. Interesting about this technique is its ability to accommodate with non-linear heterogeneous surfaces due to the sewing-needle like microelectrode that moves up and down alternatively without ruining the non-flat superficial. As such, our aim in this project is to exploit the advantages of the SEPM techniques in order to study and monitor the synergistic effect between the fatigue and the corrosion behavior on the surface of some metals.
Site-Selective Modification of Conductive Materials By Bipolar Electropolymerization
Authors: Inagi Shinsuke , Koizumi Yuki , Watanabe Tempei , Zhou Yaqian , Shida Naoki , Nishiyama Hiroki , Tomita Ikuyoshi
Published: May 2020

Electrooxidative coupling polymerization of aromatic monomers affords π-conjugated polymers. Conducting polymers are generally insoluble in solvents and are thus deposited on the surface of an anode during polymerization. This film formation is one advantage of electropolymerization because the chemical oxidative polymerization of aromatic monomers using chemical oxidants affords only insoluble powder or bulk of the corresponding polymers. This advantage is potentially useful for wide variety of applications, such as in electronics and sensors.

Recently, bipolar electrodes (BPEs) are available as wireless electrodes that undergo anodic and cathodic reactions at their terminals. When electropolymerization of aromatic monomers is conducted on a BPE, which is known as bipolar electropolymerization, this results in the wireless and site-selective formation of conducting polymer films or clusters at one terminal of the BPE. The alternating current (AC) bipolar electropolymerization of 3,4-ethylenedioxythiophene (EDOT) successfully provides microfibers of the corresponding polymer, poly (3,4-ethylenedioxythiophene) (PEDOT), grown from both terminals of the BPE. In this context, the bipolar method is next-generation electropolymerization that can site-selectively modify wireless electrodes with conducting polymers to afford novel hybrid materials. Herein, the concept of bipolar electropolymerization and recent examples are described.