bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploring the Local Optoelectronic Properties of ALD Grown TiO2 Photoelectrode-Coatings with Atomic Force Microscopy Methods
Authors: Pourmahdavi Maryam , Raudsepp Ragle , Fengler Steffen , Kriegel Herman , Kollmann Jiri , Klassen Thomas , Schieda Mauricio , Toma Francesca Maria 
Published: February 2024

Photoelectrochemical cells (PECs) hold great promise as an environmentally friendly method of converting sunlight into valuable fuels. However, the semiconductor components of PEC photoelectrodes are susceptible to corrosion under photoelectrochemical conditions.
In order to protect the surface of these semiconductors from degradation, a thin overlayer of Titanium dioxide (TiO2) is often applied by atomic layer deposition (ALD). In addition to their protecting function, the physicochemical properties of these thin films significantly affect the overall performance of the device. The local nano-scale optoelectronic characteristics, which considerably influence their macroscopic properties, have rarely been reported in the literature.
AFM methods constitute a powerful tool to investigate photo-induced charge separation, charge transport and recombination on photoelectrode surfaces with nanometer resolution.
In this context, we have employed Tunneling Conductive AFM (TUNA) and Kelvin Probe Force Microscopy (KPFM) in the dark and under illumination to investigate the surface of ALD-grown TiO2. The synthesis conditions determine the morphology, which has a strong impact on the local optoelectronic properties. TUNA measurements reveal higher photogenerated currents on the grain and facet boundaries, showing that these regions can be favorable conduction pathways. Based on KPFM experiments we can quantify the more efficient photo-induced charge separation on the crystalline TiO2 inclusions, which generate a significant surface photopotential (~450 mV) upon UV-illumination. Categorization of different regions of surface topography based on morphology allows us to analyze the evolution of surface potential over time and extract localized time constants for carrier dynamic processes on the films. This spatially resolved information provides valuable insight to guide the development of macroscopically stable and efficient photoelectrodes through the engineering of microstructure at the nano scale.
Improvement of Oxygen Reduction Reaction Performance of Fe-N-C Catalyst
Authors: Nakamura Genki , Tanaka Hirohisa 
Published: February 2024

Fuel cells are gaining worldwide attention as an acceptable technology for achieving carbon neutrality. However, existing fuel cells use large amounts of precious metals, which limits their widespread adoption. Precious metal-free fuel cells have been studied in our laboratory. The oxidation-reduction reaction (ORR) at the cathode of the fuel cell must start at a higher potential and proceed smoothly in a four-electron reduction reaction without producing hydrogen peroxide1,2. We have synthesized iron-based complex catalysts using the method reported by Plamen Atanassov3 et al. Iron nitrate dihydrate is mixed in aqueous solution with glucose, 2-methylimidazole, and zinc nitrate hexahydrate, followed by hydrothermal synthesis at 200°C for 24 hours. It is then acid-treated with nitric acid to dissolve excess metallic iron, and the process is repeated twice at 950°C to complete the Fe-N-C catalyst. However, SEM and XRD analysis confirmed the presence of large amounts of metallic iron. In response to these results, the synthetic process of the Fe-N-C catalyst was repeatedly improved, and the prepared catalyst was subjected to in-situ XAFS (X-ray absorption fine structure) analysis using synchrotron radiation at SPring-8 (Fig. 1). The peak around 7110 eV is significantly different from that of metallic iron (Fe foil), indicating that iron complex, iron phthalocyanine (II), and it is like the peak of iron phthalocyanine (II), confirming that the prepared Fe-N-C catalyst forms a good complex. The performance of the Fe-N-C catalyst with the confirmed complexation was then investigated, and a cathode that exhibited ORR performance comparable to that of the Pt catalyst was successfully synthesized (Fig. 2). In the future, further improvement of the catalyst preparation process will be discussed to develop a catalyst with much better performance than Pt.
Reference

1N. Yamamoto, D.Matsumura, Y. Hagihara, K.Tanaka, Y. Hasegawa, K. Ishii, H. Tanaka, “Investigation of hydrogen superoxide adsorption during ORR on Pt/C catalyst in acidic solution for PEFC by in-situ high energy resolution XAFS”, Jounal of Power Sources, 557, 15, (2023), 232508

2S. Kusano, D. Matsumura, K. Ishii, H. Tanaka, J. Mizuki, “Electrochemical Absorption on Pt Nanoparticles in alkaline Solution Observed Using in-situ High Energy Resolution X-ray Absorption Spectroscopy”, Nanomaterials, 9, 4, (2019), 642

3 R. Gokhale, L-K. Tsui, K. Roach, Y. Chen, M. M. Hossen, K. Artyushkova, F. Garzon, p. Atanassov, “Hydrothermal synthesis of platinum-Group-Metal-Free Catalysts: Structural Elucidation and Oxygen Reduction Catalysis”, ChemElectroChem, 5, 14, (2017), 1848-1853

Figure 1
Synthesis of Ir Nanoparticles As Promoters for the Stabilization of Fenc-Catalysts Under Ssc Conditions
Authors: Sondershausen Lars , Gridin Vladislav , Segura Salas Nicole , Hofmann Kathrin , Kramm Ulrike I. 
Published: February 2024

Fuel cells are promising devices for implementation in automotive propulsion. While the standard operation seems feasible, during start-up and shutdown high potentials occur on the cathodic site induced by the reverse current mode. In consequence, the carbon oxidation reaction (COR) occurs and limits the lifetime of PEMFCs. One approach suppressing carbon corrosion is the introduction of small amounts of an oxygen evolution reaction (OER) catalyst, as e.g. iridium. In our recent work we showed that in relative manner the durability was improved, however, the initial performance was less compared to the non-modified FeNC catalyst.[1
] These NP had been prepared by a polyol approach.[2
] However, capping agents (CA) could eventually still be present in these systems, blocking the particles in their performance.
Herein, we present our results using an alternative surfactant free synthesis of Ir nanoparticles, adapted from literature,[3
] that are then used for the modification of an FeNC catalysts. The performance of the newly prepared FeNC+Ir vs the FeNC+Ir+CA reference was evaluated employing accelerated stress tests mimicking the start-up and shut down conditions in RDE and PEMFC. It is shown that with this new approach the amount of NP on the surface can be better controlled. Beside the electrochemical testing structural characterization by X-ray-diffraction, thermogravimetric analysis and transmission-electron-microscopy was performed.
It will be shown that by surfactant free synthesis Ir nanoparticles with high purity can be obtained. Due to the higher purity, an improvement of the OER activity can be achieved with the same Ir loading. In the RDE, an improvement in stability was observed by loading an FeNC catalyst with Ir nanoparticles. However, under fuel cell conditions, no improvement in stability was observed by loading Ir nanoparticles onto a FeNC catalyst.
List of references
[1] Prössl, C., Kübler, M., Paul, S., Ni, L., Kinkelin, S. J., Heppe, N., Eberhardt, K., Geppert, C., Jaegermann, W., Stark, R. W., Bron, M. & Kramm, U. I. (2022). Impact of Ir modification on the durability of FeNC catalysts under start-up and shutdown cycle conditions. Journal of Materials Chemistry A, 10(11), 6038-6053.
[2] Prössl, C., Kübler, M., Nowroozi, M. A., Paul, S., Clemens, O., & Kramm, U. I. (2021). Investigation of the thermal removal steps of capping agents in the synthesis of bimetallic iridium-based catalysts for the ethanol oxidation reaction. Physical Chemistry Chemical Physics, 23(1), 563-573.
[3] Bizzotto, F., Quinson, J., Schröder, J., Zana, A., & Arenz, M. (2021). Surfactant-free colloidal strategies for highly dispersed and active supported IrO2 catalysts: Synthesis and performance evaluation for the oxygen evolution reaction. Journal of catalysis, 401, 54-62.
Causes and Effects of Unintended Cation Crossover in CO2 Reduction Cells
Authors: El-Nagar Gumaa , Haun Flora , Gupta Siddharth , Stojkovikj Sasho , Mayer Matthew T. 
Published: February 2024

Electrochemically converting carbon dioxide into useful products is a promising approach to combat climate change by reducing our reliance on fossil fuels and promoting a sustainable carbon cycle.
The operation of membrane electrode assemblies within gas diffusion cells facilitates the efficient reduction of CO2 at rates relevant to industrial applications. However, their long-term stability is often limited by formation of solid precipitates in the cathode pores. This is a consequence of a combination of 1) local alkalization due to the electrochemical reaction, 2) generation of (bi)carbonate by chemical reaction of CO2 with the alkaline electrolyte, and 3) the presence of alkali metal cations. In catholyte-free, zero-gap cells using anion exchange membranes, the presence of electrolyte cations at the cathode is the result of unintended crossover from the anolyte, and a detailed understanding of the factors enabling this crossover is lacking. Here we show that the anolyte concentration governs the flux of cation migration through the membrane, and this substantially influences the behaviours of copper catalysts in catholyte-free CO2 electrolyzers.
Our findings highlight the substantial impact of cation effects, including unintended crossover, even in catholyte-free cells, on reaction pathways. This aspect should be considered in the future development of catalysts and devices. As an outlook a more in-depth knowledge with the help of operando measurements could help to understand and manage cation crossover for optimizing the performance, selectivity, and durability of these electrochemical systems.
Ultra-Low Loading IrO2 on Porous Transport Layer for Catalysis of Proton Exchange Membrane Water Electrolysis
Authors: Shen Jie , Bens Frennie , van Dijk Bas , Ripepi Davide , Diaz-Morales Oscar 
Published: February 2024

Proton Exchange Membrane Water Electrolysis (PEMWE) is a commercial technology with specific advantages such as high-power density and rapid start-up times, which makes it a perfect match to produce hydrogen from intermittent renewable energy sources (green H2). [1] However, very scarce materials, such as iridium and platinum, are currently used as catalysts and protection coatings to withstand the harsh operating conditions in PEMWE. Iridium is the anode catalyst in the state-of-the-art PEMWE, with loadings in the range 1-2 mg/cm2. This metric translates into using 200-500 kg of iridium per GW, which accounts for roughly 10% of the global iridium production per year. Reducing iridium usage in PEMWE is critical to realize the 10-100 GW/year growth in green H2 power. [2,3]
To significantly reduce the Ir loading, while maintaining the lateral conductivity, we coated the iridium catalyst by atmospheric spatial Atomic Layer Deposition (sALD) on titanium porous transport layer (PTL), which acts as the electrically conductive substrate. The coating renders ultra-low iridium loadings, which is 100-200 times less iridium than the state-of-the-art catalyst coated membrane technology, while retaining ca. 60-80% of the performance (in terms of current density), with durability demonstrated up to 100 h (see Figure 1). We will also show here that protection coatings on the titanium PTL are beneficial to yield good durability with these ultra-low loadings of iridium and demonstrated that sALD has the potential to produce non-PGM based protection coatings.
[1] Barbir, F. Solar Energy 78 (2005) 661-669.
[2] Gavrilova, A., Wieclawska, S.M. “Towards a green future. Part 2” (2021). TNO report 21-12158.
[3] Minke, C., Suermann, M., Bensmann, B., & Hanke-Rauschenbach, R. J. Hydrogen Energy 46 (2021) 23581-23590.

Figure 1
Tailoring Binding Abilities By Incorporating Oxophilic Transition Metals on 3D Nanostructured Ni Arrays for Accelerated Alkaline Hydrogen Evolution Reaction
Authors: Kim Jaerim , Jung Hyeonjung , Jung Sang-Mun , Kim Yong-Tae , Han Jeong Woo , Kim Jong Kyu 
Published: February 2024

Developing efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role for renewable hydrogen energy technology. The slow reaction kinetics of HER in alkaline solutions, however, has hampered advances in high-performance hydrogen production. Herein, we investigated the trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities. In particular, Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media. Further enhancement of catalytic performance was achieved by introducing an array of three-dimensional (3D) Ni nanohelixes (NHs) that provide abundant surface active sites and effective channels for charge transfer and mass transport. The Cr dopants incorporated into the Ni NHs accelerate the dissociative adsorption process of water, resulting in remarkably enhanced catalytic activities in alkaline medium. Our approach can provide a rational design strategy and experimental methodology toward efficient bimetallic electrocatalysts for alkaline HER using earth-abundant elements.
Reference

Journal of the American Chemical Society 3, 1399-1408 (2021) [Front Cover]
LiMn2O4 as a Model System to Understand the Mn Dissolution Mechanism during Water Oxidation
Authors: Bisen Omeshwari Yadorao , Baumung Max , Schönewald Florian , Volkert C. a. , Risch Marcel 
Published: February 2024

LiMn2O4 as a model system to understand the Mn dissolution mechanism during water oxidation

Omeshwari Bisen1,2, M. Baumung1,2, F. Schönewald2, C. A. Volkert2, M. Risch1,2

1

Nachwuchsgruppe Gestaltung des Sauerstoffentwicklungsmechanismus,
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1,14109 Berlin, Germany

2

Institut für Materialphysik, Georg-August-Universität Göttingen, Germany

Email: omeshwari.bisen@helmholtz-berlin.de

The water splitting provides an attractive avenue for chemical energy storage by producing the green hydrogen, but it suffers from the inefficiency of the oxygen evolution reaction (OER) and the degradation of the electrocatalyst under the harsh oxidizing conditions of the reaction. Manganese oxides are attractive due to their abundance and as a non-critical raw material, but they are known to degrade quickly during the OER, which hinders their usage severely. [1] Therefore, it is equivalently important to focus on the understanding of degradation processes during the OER. [2]
In this study and our previous studies, we used the battery material LiMn2O4 as a model system for the OER in alkaline media where the Mn valence can be tuned with little effect on structure. [3, 4] LiMn2O4 exhibits a core-shell cubic-spinel structure with tetrahedral antisite Mn2+ defects in the shell. [5] We have used the rotating ring-disk electrode (RRDE) setup to obtain the product current of manganese corrosion and oxygen evolution by applying the desired potential at the Pt ring (Fig. 1a). We monitored the dissolution of Mn from the LiMn2O4 (Fig. 1b) and found two onsets of exponential currents, indicating the two distinct Mn loss processes; one independent of the OER and one associated to it, which is further investigated by Tafel slopes. The ex-situ X-ray absorption spectroscopy (Fig. 1c) and X-ray photoelectron spectroscopy (Fig. 1d) represents the oxidation of Mn moieties after voltage cycling including the OER, and loss of Mn2+
and Li+. We correlate near-surface oxidation with the charge attributed to dissolved Mn, which demonstrates increasing Mn dissolution with the formation of surface Mn4+ species under anodic potential and observed the distinct atomistic origin before and after OER onset.[6] It is highly desirable to understand the atomistic insights into the Mn dissolution processes for the knowledge-guided mitigation of electrocatalyst degradation during water oxidation, which can be broadly extended to manganese-based oxide systems.

References:

[1] M. Rabe et al., Phys. Chem. Chem. Phys., 2019, 21, 10457

[2]M. Risch,Current Opinion in Electrochemistry2023, 38:101247

[3] M. Baumung et al., ChemPhysChem 2019, 20, 2981-2988

[4] M. Baumung et al., Sustain. Energy Fuels 2019, 3, 2218-2226

[5] F. Schönewald et al. arXiv:2007.04217v1 [6] O. Bisen et al. arXiv preprint arXiv:2309.00101

Figure 1
Prediction of 4f-5d Transition Energy of Ce3+ in Oxides By First-Principles Calculations and Machine Learning
Authors: Honda Mamoru , Ogasawara Kazuyoshi 
Published: February 2024

A Ce3+ ion has only one electron in the 4f orbitals and its 4f-5d transition energy is strongly influenced by the width of the crystal field splitting of the 5d orbitals. In other words, the absorption and emission wavelengths of Ce3+ in crystals can be widely controlled by changing the ligand field environment. As an example of Ce3+-doped phosphor, Ce:YAG (Y3Al5O12) is widely used as an yellow phosphor for standard white LEDs. Therefore, novel phosphors with desired emission colors can be developed by adding Ce3+ to appropriate host crystals.
In this work, we aimed to construct an efficient prediction model for the transition energy of Ce3+ in oxide crystals. Small clusters consisting of the substituted Ce3+ ion and the first-neighbor anions were constructed and molecular orbital calculations were performed using the relativistic discrete-variational Xα (DV-Xα) method. Then machine learning based on structural and electronic state parameters was performed to create a predictive model for the 4f-5d transition energy of Ce3+ in crystals. By creating the correlation diagrams, the influence of each parameter on the transition energy was analyzed in detail.
Optimization of the First-Principles Calculation Conditions of d3 Ions in SrTiO3
Authors: Okada Sayaka , Tanaka Shuma , Ogasawara Kazuyoshi 
Published: February 2024

Since transition metal ions are generally more stable in supply than rare earth ions and are inexpensive, researches on alternative materials based on transition metal elements to those based on rare earth elements are actively conducted. As phosphors using transition metal ions, Cr3+ and Mn4+ with d3 configuration are used for red emission while Mn2+ with d5 configuration is used for green emission. For theoretical search of novel phosphor materials, first-principles calculations of the transition energies based on the cluster approach are useful. However, in order to establish an efficient and effective method for prediction, optimization of computational conditions is indispensable.
In this study, first-principles calculations of the d-d transition energies of d3 ions such as Cr3+ and Mn4+ in SrTiO3 were performed using the discrete-variational multi-electron (DVME) method. The clusters with Ti4+ at the center were constructed based on the crystal structure data of SrTiO3, and then Ti4+ was replaced with Cr3+ or Mn4+. In order to determine an appropriate cluster size, model clusters consisting of 7, 15, 63, 89, 143, 199, and 391 atoms were constructed. In order to improve the accuracy, the first-principles calculations were carried out considering the configuration-dependent correction (CDC) and the correlation correction (CC), which correct the overestimation of the multiplet energies. The effect of the lattice relaxation was also considered based on the structural optimization using the CASTEP code. Then the cluster size dependence and the effect of the lattice relaxation were clarified based on the detailed comparison of the first-principles calculation results.
(Digital Presentation) One-Step Hydrothermal Preparation of Chiral Carbon Quantum Dots and Its Chiral Recognition of Glutamine Enantiomers
Authors: Zhu Xiashi , Li Xiang 
Published: February 2024

Abstract: A novel method for chiral recognition of glutamine enantiomers using fluorescence intensity changes of chiral carbon quantum dots(CCQDs) is proposed. CCQDs was prepared by one-step hydrothermal method with L-tryptophan as carbon source and chiral source, which are spherical nanoparticles exhibiting blue color luminescence for fluorescence probe to recognize glutamine enantiomeric isomers[1] . Fluorescence intensity(∆Fe )enhanced by addition of L-glutamine to CCQDs solution and ∆Fe was well linear with L-glutamine concentration in the range 0.01-5.0 mM and the limit of detection was 0.22 mM. Fluorescence quenching(∆Fq) by D-glutamine addition to CCQDs solution and ∆Fq was well linear with D-glutamine concentration in the range of 0.01-5.0 mM with a detection limit of 0.28 mM. Calculation of the binding energy between L/D-glutamine and CCQDs by molecular modelling to explain the chiral recognition mechanism[2,3]. The method was applied to the determination of L-glutamine content in real sample and the results showed good recoveries, indicating the feasibility of the method.

References:

[1] F. Copur, N. Bekar, E. Zor, S. Alpaydin, H. Bingol, Nanopaper-based photoluminescent enantioselective sensing of L-Lysine by L-Cysteine modified carbon quantum dots, Sensors and Actuators B: Chemical. 279 (2019) 305–312. https://doi.org/10.1016/j.snb.2018.10.026.
[2] O. Xu, S. Wan, Y. Zhang, J. Li, X. Zhu, A unique dual-excitation carbon quantum dots: Facile synthesis and application as a dual-“on-off-on” fluorescent probe, Sensors and Actuators B: Chemical. 340 (2021) 129904. https://doi.org/10.1016/j.snb.2021.129904.
[3] X. Hou, J. Song, Q. Wu, H. Lv, Chiral carbon quantum dots as fluorescent probe for rapid chiral recognition of isoleucine enantiomers, Analytica Chimica Acta. 1184 (2021) 339012. https://doi.org/10.1016/j.aca.2021.339012.
Anodic Chlorination of Poly(3-(2-ethylhexyl)Thiophene) Films Facilitated by Constructing Ordered Structures
Authors: Kurioka Tomoyuki , Tomita Ikuyoshi , Inagi Shinsuke 
Published: February 2024

π-Conjugated polymer (CP) is known to show unique optoelectronic properties due to their extended π-conjugation moieties along with their main chains.[1] To control these properties, post-functionalization methods are powerful approaches. Among post-functionalization methods, electrochemical post-functionalization (ePF) is a useful and promising approach to manipulate the optoelectronic properties of the film-state CPs.[2] Considering their optoelectronic properties in the film state, these properties are often affected by their structures. On the basis of this idea, the structure of CP films is expected to serve a crucial role in the efficacy of ePF; however, the relationship between their structures and ePF methods remains unexplored.
In this work, we report the relationship between the structures of CP films and the efficacy of ePF by performing anodic chlorination of poly(3-(2-ethylhexyl)thiophene) (P3EHT) films (Figure 1).[3] Changing solvents used in preparing P3EHT films is found to result in P3EHT films with different structures (i.e., amorphous and crystalline structures). The amorphous P3EHT films are not electrochemically chlorinated, whereas P3EHT films possessing crystalline domains are successfully chlorinated in the same reaction conditions. In situ conductance measurements of P3EHT films evidence that the reactivity difference in the anodic chlorination between both P3EHT films is because of their electrical conductivity.

References

[1] X. Guo, M. Baumgarten, K. Müllen, Prog. Polym. Sci.
2013, 38, 1832–1908.
[2] T. Kurioka, S. Inagi, Chem. Rec.
2021, 21, 2107–2119.
[3] T. Kurioka, T. Komamura, N. Shida, T. Hayakawa, I. Tomita, S. Inagi, Macromol. Chem. Phys.
2022, 223, 2100435.

Figure 1