bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic Activity of Atomic Metals Clusters Decorated Polyaniline Electrodes in Electrochemical Oxidation of 1-Propanol
Authors: Yoshida Shohei , Okamoto Keisuke , Kurioka Tomoyuki , Chen Chun-Yi , Chakraborty Parthojit , Nakamoto Takamichi , Sone Masato , Chang Tso-Fu Mark
Published: February 2024

Electrochemical sensors are capable to fast-detect chemicals with a high sensitivity at a low cost. Thanks to these advantages, electrochemical sensors are promising for detections of biomolecules, such as glucose, dopamine, uric acid, etc. The catalytic electrode in a electrochemical sensor is composed of noble noble metals, such as Au and Pd,and a suppoorting material. Polyaniline (PANI)[
1]is an ideal supporting material for noble metal clusters because of its good electrical conductivity, high stability, large active surface area, and simple preparation process. Recently, PANI decorated with atomic level noble metal clusters is report to show distinct catalytic activity for the electrochemical oxidation of alcohols.[1] However, the effects of the number of the metal atoms in such clusters and the sequence of the atomic level deposition step on their electrocatalytic activity for electrochemical alcohol oxidation remain unexplored.

In this presentation, the effects of the number of the metal atoms and the sequence of the atomic level deposition step in the atomic level noble metal clusters on the catalytic activity in electrochemical oxidation of 1-propanol (1-PrOH) are reported. The PANI was deposited on a Pt disk electrode (ϕ = 3 mm) by electrochemical polymerization in a 2 M HBF4 aqueous solution containing 0.1 M of aniline. Then, the PANI deposited electrode was decorated with mono-atomic noble metal clusters, bi-atomic, tri-atomic, or tetra-atomic noble metal clusters. The atomic noble metal clusters are denoted as PdxAuy, where x represents the number of Pd atoms in a cluster and y is the number of the Au atoms. The sources of the Pd and Au were K2PdCl4 and KAuCl4, respectively.. Fig. 1 shows the schematic procedures for fabricating a bi-atomic pure Pd (Pd2) decorated PANI electrode and a PdAu decorated PANI electrode. The catalytic activity for the electrochemical oxidation of 1-PrOH was evaluated by performing cyclic voltammetry measurements with an aqueous solution containing 0.5 M 1-PrOH and 1 M KOH.

The catalytic activtiy was found be higher for the Pd2 and Pd4 decorated PANI electrodes than those of the Pd1 and Pd3 decorated PANI electrodes, which revealed odd-even pattern effects as reported in a previous study.[
1] Furthermore, the catalytic activity was found to be affected by the sequence in deposition of the atomic level noble metal clusters.

Reference

[1] A. P. Jonke, J. L. Steeb, M. Josowicz, J. Janata, Catal Lett
2013, 143, 531–538.

Figure 1
Self-Terminated Surface Reconstruction of Lanthanum Nickelates Promotes Alkaline Oxygen Evolution
Authors: Wu Yi-Hsuan , Janák Marcel , Abdala Paula M. , Kuznetsov Denis A. , Müller Christoph R.
Published: February 2024

Oxygen evolution reaction (OER) itself is expected to have a strong impact on the state of the surface of the electrocatalyst, yet the actual structure of the surface under operating conditions is rarely considered while formulating structure-activity correlations in electrocatalysis. In this study, changes in the surface structure of Ruddlesden-Popper-type lanthanum nickelate, La2NiO4+δ, and the perovskite LaNiO3 are probed and contrasted using a series of complementary surface sensitive techniques, including XPS, HRTEM and O K-edge XAS. We found noticeable surface changes to occur on La2NiO4+δ after exposure its exposure to the alkaline electrolyte that is accompanied by the emergence of a strong Nin+/n+1 redox feature and the coincides with a 45-fold enhancement of the OER activity (at η = 370 mV) in 0.1 M KOH, as compared to the pristine La2NiO4+δ phase. We observe that the in situ formation of an amorphous nickel (oxy)hydroxide layer on the surface increases the electrochemically-active surface area of La2NiO4+δ and imparts a high stability of the catalyst under OER conditions (the formation of the amorphous layer self-terminates at ca. 3 nm). In addition, the transition from octahedral Ni sites (O
h
) to square-planar Ni sites (D
4h
) in the reconstructed surface was observed using O K-edge X-ray absorption spectroscopy. Further, we found no evidence for any surface transformations in the perovskite-based catalyst LaNiO3 that also did not demonstrate any improvement in its activity over cycling. This work highlights the importance of a detailed surface analysis of the catalysts under operation to build robust structure-activity correlations for the metal oxides under electrochemical reaction conditions.

Figure 1
Multiphysics Electrochemical Impedance Simulations of Complex Multiphase Electrodes
Authors: Qu Danqi , Yu Hui-Chia
Published: February 2024

Electrochemical impedance spectroscopy (EIS) is a widely used technique for characterizing materials in electrochemical systems. However, directly connecting the obtained quantities to microstructure-level phenomena is challenging. In this work, we performed detailed electrochemical microstructure simulations to investigate the EIS behavior of phase-separating graphite electrodes. We employed the Cahn-Hilliard phase-field equation to model Li transport and phase transitions in the graphite particles. In single-phase graphite particles, the charge-transfer resistance reflected the total active surface areas. In two-phase coexistence graphite particles with phase boundaries present on the particle surfaces, the simulations exhibited an inductive loop on the EIS curve. In core-shell phase-morphology cases, the EIS measurements reflected only the properties of the shells. The resulting EIS curves were indistinguishable from those in the single-phase cases. While Fick's law of diffusion has been mistakenly employed to model Li transport in phase-separating graphite electrodes, our simulations showed that the EIS curves obtained using the Fickian diffusion model were very similar to those obtained using the Cahn-Hilliard phase-field model. This tool provides unprecedentedly detailed simulations to connect the intrinsic material properties, electrochemical processes in the microstructures, and resulting EIS behavior.

Figure 1
DFT Simulations on the Nitrogen Reduction Reaction Activity of Transition Metal Nitride and Oxynitride
Authors: Liu Ji , Glauber Jean-Pierre , Lorenz Julian , Bragulla Sebastian , Müller Björn , Harms Corinna , Wark Michael , Devi Anjana , Nolan Michael
Published: February 2024

Transition metal nitride (TMN) is a promising material towards the energy related applications including catalysis and energy storage.1 The sluggish nitrogen reduction reaction (NRR) due to the high energy input to activate N2 remains a significant challenge for NRR electrocatalysts. The surface N of TMN can be a solution to this with initial N vacancy formation via hydrogenation steps and ammonia formation. In addition, with a small amount of surface oxygen present in the catalyst surface, the resulting oxynitride seems very interesting and active towards NRR.2 But the mechanism behind this is not yet understood.

In this study, we first focused on the modelling of the structure of metal nitride (ZrN) and oxynitride (ZrOxNy/ZrN) surfaces. The structure of oxynitride is obtained by running molecular dynamics (MD) calculations at both room temperature and experimental deposition temperature (90°C and 750°C). NRR reaction is then studied via the Mars-Van Krevelen (MvK) mechanism with introducing surface N vacancy and subsequent N2 adsorption and N filling. With computing the reaction energy and activation barriers of key reaction steps on both ZrN and ZrOxNy/ZrN, we can find a clue on how surface N of TMN helps to activate N2 and the role of small amount of surface oxygen on activating N2. To study the origin of small amount of oxygen, reaction energies and full reaction pathway along the deposition process are computed and plotted. Finally, dopant effect will be modeled with transition metal dopants (e.g. Cu and Hf) at surface region to study any localized electronic effect on NRR.

These results can be useful to design and deposit ZrN acting as effective NRR electrocatalysts.

References

[1] Luo, Q.; Lu, C.; Liu, L.; Zhu, M., A review on the synthesis of transition metal nitride nanostructures and their energy related applications, Green Energy & Environ. 2023, 8, 406

[2] Young, S. D., Ceballos, B. M., Banerjee, A., Mukundan, R., Pilania, G., & Goldsmith, B. R, Metal Oxynitrides for the Electrocatalytic Reduction of Nitrogen to Ammonia. J. Phys. Chem. C. 2022, 126, 12980-12993.
Choice of Surfactants and Its Impact on the Capacitive Behaviour of PEDOT-Carbon Nanotubes Composites Synthesised at the Liquid|Liquid Interface
Authors: Rojas-Sanabria Nicolas , Quintero Jaime Andrés Felipe , Holzinger Angelika , Scanlon Micheal D.
Published: February 2024

Conductive polymers (CP), such as poly(3,4-ethylenedioxythiophene) (PEDOT), exhibit exceptional physical, chemical, and electrical properties [1] that position them as effective alternatives for the manufacture of electrode materials for energy storage applications [2]. In order to increase the stability of the polymer, and thus extend the lifespan of the supercapacitor device, surfactants are added to the polymer matrix [3]. Among the most used surfactants, poly(styrenesulfonate) (PSS) has shown to enhance the stability of polymers and has positioned itself as the surfactant of preference while working with PEDOT. However, a decrease in the capacity and conductivity of the material is also exhibited [4]. Here, the addition of differently charged surfactants during the four-electrode polymerisation of PEDOT at a polarised aqueous|organic interface (ITIES) was studied under ambient conditions. The results show a considerable effect of the surfactant on the morphology of the polymer that translates into a change of the charge storage capacity. Cetyltrimethyl ammonium bromide (CTAB) shows potential as a suitable alternative to PSS for the synthesis of CP-CNT composites. Finally, multi-walled carbon nanotubes (MWCNTs) are dispersed on the aqueous phase containing the surfactant and later incorporated into the polymer film during the interfacial synthesis of PEDOT-MWCNT composites.

References

[1] C. Zhan et al., J. Mater. Chem. C. 2017, 5(7):1569-85

[2] I. Gualandi et al., Sci. Rep. 2016, 6, 35419.

[3] Q. Yang et al., J. Electroanal. Chem., 2014, 728, 140-147.

[4] R.A. Lehane, et al., J. Am. Chem. Soc. 2022 144 (11), 4853-4862

Figure 1
Hydrogen Reduction Reduction (HRR)
Authors: Wang Hai-Xu , Surendranath Yogesh
Published: February 2024

The year 2023 marks the bicentennial of the discovery of heterogeneous H2 catalysis. Nowadays, the hydrogen oxidation reaction (HOR), which converts H2 to protons (H+), is one of the most important transformations in energy research. Meanwhile, hydrogenation reactions, which transfer net H-atoms (H·) to organic substrates from H2, play pivotal roles in various chemical industries. In comparison, it is surprising to see that a heterogenous catalytic reaction that directly converts H2 to hydrides (H–) still remains elusive. Hydride transfer is a critical elementary reaction step that spans biological catalysis, organic synthesis and energy conversion. Conventionally, hydride transfer reactions are performed using (bio)molecular hydride reagents under homogeneous conditions. Here we report a conceptually distinct heterogeneous hydride transfer reaction via the net electrocatalytic hydrogen reduction reaction (HRR), which reduces H2 to hydrides. The reaction proceeds by H2 dissociative adsorption on a metal electrode to form surface M−H species, which are then negatively polarized to drive hydride transfer to molecular hydride acceptors with up to 91% Faradaic efficiency. The hydride transfer reactivity of surface M−H species is highly tunable, and, depending on the electrode potential, the thermodynamic hydricity of Pt−H on the same Pt electrode can continuously span a range of >40 kcal/mol.

In addition to this electrochemical transformation, we further developed an alternative strategy to achieve heterogeneous hydride transfer on dispersed metal catalysts under non-electrochemical conditions. In the presence of a base, deprotonation of surface M-H builds up electron density at the metal surface and thereby causes spontaneous polarization which can then drive hydride transfer from metal nanoparticles. Based on this, HRR can be performed under standard hydrogenation conditions with the addition of a base using dispersed metal catalysts, and the surface hydricity is now controlled by the solution basicity. We further demonstrate that this non-electrochemical HRR method can be applied to NADH regeneration which is closely related to industrial biocatalysis. The discovery of HRR reveals the fundamental hydride transfer reactivity of surface M-H species as well as its polarization-dependent nature. Both the electrochemical and non-electrochemical HRR methods establish sustainable strategies for accessing reactive hydrides directly from H2.

Figure 1
Morphology of RuO2(110) Films during Electrochemistry
Authors: Reese Austin Jerad , Wadehra Neha , Suntivich Jin , Schlom Darrell
Published: February 2024

RuO2 is a well-known electrocatalyst for the oxygen evolution reaction (OER), a critical electrochemical reaction in the water electrolyzer. The behavior of RuO2 during the OER is, however, a subject of debate, in particular, the corrosion mechanism. In this contribution, we report an electrochemical AFM (EC-AFM) study on well-defined RuO2 films grown using molecular beam epitaxy (MBE). We track the morphology of step edges prior, during, and after the OER in acid and alkaline electrolytes to gain insights into the corrosion behavior. Our EC-AFM experiment shows the potential range of RuO2 corrosion and hints at the role of strain and defects in the RuO2 stability. The heterogeneity of corrosion will be discussed in the context of the catalyst longevity along with possible mitigation strategies.
(Digital Presentation) Development of a Low Cost Pencil Lead Electrode for Simultaneous Detection of Amoxicillin and Uric Acid
Authors: Kabiraz Dulal Chandra , Hasan Rakibul
Published: February 2024

Herein, we develop a low-cost pencil graphite (PG) by amine-functionalization and employed for the first time, as an electrochemical transducer for the detection of amoxicillin (AMX). The electrochemical characterization results revealed that amination enhanced 2.17 times surface area than bare PGE. The pH of supporting electrolyte solution significantly influenced the electrochemical response of AMX oxidation. Besides, the experimental data revealed that AMX oxidation is irreversible, and diffusion-controlled process. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) technique are applied to quantitative determination of AMX. From the constructed calibration plot, a linear range from 2.5 µM to 300 µM with a detection limit (LOD) of 1.1028 µM was obtained for APGE using CV. While a wide linearity of 1µM to 325 µM and a LOD of 0.0113 µM were achieved by using DPV. The electrode was then applied for the simultaneous quantification of AMX and UA. In simultaneous detection the LOD was estimated to 0.964 µM, and 0.8876 µM for AMX and UA, respectively. The sensor substrate was tested in the presence of different potential interfering agent such as fructose, ascorbic acid, valine, sucrose, proline, histidine, glutamic acid, glycine, serine, phenylalanine, aspartic acid, creatinine, arginine, ampicillin, Na+, K+, Ca2+, Cd2+, Cl-, SO4
2-, NO3
-, Zn2+, Ba2+, and Pd2+. Furthermore, how long the modified electrode can alive was checked and a satisfactory reproducibility up to 37 weeks was found. Finally, the sensor substrate was applied for real samples as example in pharmaceutical formulation, in spiked urine, and in cow urine.
Interfacial Structures of Heterogeneous Systems Determined by Using in-Situ XAFS
Authors: Han Sang-Wook , Jeong Eun-Suk , Hwang Inhui
Published: February 2024

During chemical reactions and catalysis, the surface and interfacial structural properties of materials are considerably important to understand and control the reactions. However, in-situ measurements have many limits during reactions. We used in-situ X-ray absorption fine structure (XAFS) to understand the local structural properties at the surface and the interface of metal catalysts on transition−metal−oxide supports. Pt nanoparticles (NPs) with a mean size of ~1 nm on TiO2 supports are synthesized using an incipient wetness method. In-situ XAFS measurements are performed from the Pt NPs/TiO2 at Pt L3 and Ti K edges during heating from room temperature to 500 ℃ in an H2 environment. Fourier−transformed extended X-ray absorption fine structure (FT−EXAFS), which is a unique tool to quantitatively determine the local structural properties of materials around a selected species element, shows a lack of oxygen atoms as the nearest neighbors of Pt atoms at T = 250 ℃; meanwhile, the wavelet-transformed EXAFS (WT-EXAFS) with enhanced resolution shows a weak but distinguishable oxygen signal around Pt atoms. Pt−O bonds likely exist at the interface of Pt/TiO2, although oxygens on the outer surfaces of Pt NPs are mostly dissociated at T > 250 ℃ in an H2 environment. This finding strongly suggests that the combination of FT−EAXFS and WT−EXAFS can more accurately describe small amounts of light elements bonding with heavy elements than FT−EXAFS can alone. DFT calculations confirm that the presence of extra oxygen atoms at the interfaces of Pt NPs/TiO2, playing a critical role in the stability and the dispersion of Pt NPs.
(Invited) Advances in XPS Analysis of Battery Materials
Authors: Artyushkova Kateryna , Zaccarine Sarah , Mann Jennifer
Published: February 2024

Energy storage (batteries, capacitors) and conversion (solar cells) systems are increasing demand for vehicles, mobile electronics, and other areas as alternatives to fossil fuels.These systems are complex and multi-component with many materials and interfaces that are difficult to handle and characterize. To optimize materials properties and improve battery lifetimes, there is a pressing need for physicochemical characterization approaches with air-free handling capabilities, high spatial resolution, the ability to analyze buried interfaces without damaging the chemistry, and the need to bridge the gap by in situ and operando surface analysis.

Developments in X-ray Photoelectron Spectrometers (XPS) open up new capabilities to address these challenges. In this talk, I will discuss how we can overcome obstacles in analyzing battery materials using:

Inert environment transfer vessel: This allows for handling battery materials in an air-free environment, which is essential for preventing oxidation and other degradation reactions.

Microprobe X-ray source with <5 µm spatial resolution: This provides high spatial resolution for analyzing small areas of interest, such as SEI, dendrites and other features.

Hard X-ray source and cluster ion gun source: These allow for the analysis of buried interfaces not accessible by conventional soft X-ray XPS.

In situ energy gap measurements: These allow for the study of the changes in the electronic structure of battery materials as they are cycled, which can provide insights into the mechanisms of charge storage and discharge.

Operando XPS experiments: These allow for the study of the changes in the surface structure of battery materials as they are operating, which can provide insights into the factors that affect their performance.

Figure 1
Battery Thermalization for Operando Synchrotron Powder Diffraction: Application to the Ca-TiS2 System
Authors: Houdeville Raphaëlle , Fuentes Victor , Fauth Francois , Palacin M. R.
Published: February 2024

Characterizing electrode materials and understanding its behavior during redox process is a key factor for battery improvement. In Situ techniques on Operando batteries are of particular interest since they do not only probe the material during the electrochemical process but avoid its hazardous and tedious extraction and transfer under inert atmosphere from an electrochemical cell to e.g. capillaries, to perform Ex Situ data collection. Synchrotron based techniques –absorption and diffraction – together with improved detectors, are now intensively used in such In Situ studies on Operando batteries since they allow fast and real time data acquisition during the electrochemical, ion (des-)insertion, process. So far most In Situ X-ray powder diffraction studies on Operando batteries are performed at room temperature using either coin cells or so called Leriche cells [1] (pouch cells, despite widely used for spectroscopy, are generally not favored for diffraction since the container material produce additional Bragg peaks). At ALBA we slightly modified both types of cells: Leriche type and more widespread used CR2032-type coin cells so as to perform data collection in temperature range -10° – 100° C. (see picture)

Both types of cell have been used to study the intercalation of calcium in TiS2, previously determined by Ex Situ powder diffraction [2]. We managed to collect powder patterns operando at 60°C, 45°C and room temperature. (Des-)Insertion of solvated Ca2+ in TiS2 was favoured by temperature, its signature being the appearance of a new phase with a first diffraction peak at very low angles (~17.7 Å in terms of d-spacing). The process was found to be solvent dependent and reversible upon oxidation, which differs from Li cells where a similar process was observed.[3]

Either of these thermalized cells can be used at CELLS-ALBA synchrotron for Power Diffraction on BL04-MSPD beamline or hard X-ray Absorption Spectroscopy (XANES/EXAFS) on BL22-CLEASS, and since 2023 also using simultaneous Powder Diffraction and hard X-ray Absorption Spectroscopy in BL16-NOTOS beamline. Moreover, the Leriche setup is also designed to fit for a use in laboratory X-ray diffractometers, in both reflection and transmission.

Leriche et al. (2010). J. Electrochem. Soc., 157(5), A606-A610.

Tchitchekova et al (2018). Chem. Mater 30, 847−856

Houdeville et al. (2021). J. Electrochem. Soc., 168, 030514

Figure 1
Modulating Entropic Driving Forces to Promote Metal Ion Mobility in Ionic Liquids
Authors: Gebbie Matthew A. , McAlpine Jack
Published: February 2024

Ionic liquids and organic ionic plastic crystals promise to provide safer, nonflammable alternatives to the unstable organic electrolytes currently used in commercial batteries. However, the performance of ionic liquids and organic ionic plastic crystals as battery electrolytes has been hindered by poor lithium transport, in large part due to the formation of strong lithium-anion complexes. Similar ion coordination exists in ionic liquids containing dissolved sodium, magnesium, and calcium, suggesting that design of ionic liquids for sodium and multivalent battery chemistries will face similar challenges. In this talk, I will discuss our work on the design and characterization of novel ionic liquid-inspired organic electrolytes that leverage unique self-assembly properties of molecular diamond templates, called “diamondoids,” to promote selective redox ion transport. By leveraging the unique self-assembly properties of diamondoids, we show that metal cation-anion coordination can be reduced, and possibly removed, resulting in enhanced mobility of redox-active cations. Specifically, our investigation of electrolyte phase behavior, vibrational spectra, and magnetic environments demonstrates that metal salt solubility can remain high while metal cation-anion coordination is suppressed. Our results provide a new paradigm for enhancing redox species mobility in ionic liquid-derived electrolytes by engineering cation functional groups to enhance organic cation-anion interactions, suppress metal coordination, and leverage packing mismatches to enhance redox species mobility.
Electrodeposition Behavior of Al-Au Alloys in AlCl3-NaCl-KCl-Aucl Molten Salt
Authors: Sugizaki Masaya , Matsushima Hisayoshi , Ueda Mikito , Kawamura Midori
Published: February 2024

Quartz Crystal Microbalance (QCM) has been used as a highly sensitive mass sensor. This study aims to form porous gold thin films on QCM elements and apply them to highly sensitive gas sensors by attaching selective media. Physical vapor deposition and chemical etching are known methods for forming porous Au thin films. In this study, the electrochemical formation of porous gold films in AlCl3-NaCl-KCl molten salts containing AuCl was investigated. There are few reports about electrodeposition and dissolution potentials of Au in the molten salt electrolyte. As a first step in this study, voltammogram measurements and constant potential electrolysis were performed in the electrolyte, and electrodeposition potentials of Au and Al-Au alloys were discussed.

An electrolyte in this study is a mixture of 61 mol% AlCl3- 26 mol% NaCl- 13 mol% KCl molten salt. The mixture salt was melted at 443 K and AuCl was added to the molten salt. A glassy carbon plate (GC) and a pure Al wire were used as the working electrode and reference electrode, respectively. The GC plate and Au mesh were used as the counter electrode for voltammogram measurement and constant potential electrolysis, respectively. Voltammogram measurements were carried out at potential range from -0.1 to 2.4 V vs. Al/Al(Ⅲ). Constant potential electrolysis was performed in the range from -0.2 to 0.3 V with an electric charge density of 40 C cm-2. The electrodeposits were observed by scanning electron microscopy (SEM) and determined the composition of Al and Au by energy dispersive X-ray spectroscopy (EDS).

Au ions concentration in the electrolyte was 2.5 mmol dm-3. In voltammogram measurements, a small cathodic current was observed at about 0.8 V, then gradually increased from 0.2 V. In the potential lower than 0 V, a drastical increase of cathodic current was observed, which was attributed to Al electrodeposition. When the potential was reversed, large anodic current flowed from 0 V and a small current peak was also observed at 0.2 V. These were considered to correspond to the dissolution of Al and Al-Au alloys, respectively. Furthermore, a relatively large anodic current peak was observed at about 2 V, which was expected to be due to the dissolution of Au. From the results of constant potential electrolysis, the Au concentration in the electrodeposits at -0.1 V and -0.2 V was less than 1 at%. At 0 V, the Au concentration in the electrodeposit increased sharply to 84 at%, and at 0.3 V it increased moderately to 89 at%. From SEM observation, the morphology of the electrodeposits at -0.1 V and -0.2 V was dense, while that at potentials more than 0 V was sponge-like.

Acknowledgements

This work was supported by JST SICORP and JPMJSC2108.
Controlling Selectivity in Electrocatalysis By Ionic Liquids: Oxidation of 2,3-Butanediol on Pt(hkl) Electrodes Modified By [C2C1im][Otf]
Authors: Yang Juntao , Yang Tian , Franz Evanie , Deng Xin , Fromm Lukas , Taccardi Nicola , Liu Zhi , Görling Andreas , Wasserscheid Peter , Brummel Olaf , Libuda Jörg
Published: February 2024

In heterogeneous catalysis, ionic liquids (ILs) are used as chemical modifiers to control selectivity. In our work, we aim to apply the same concept to electrocatalytic systems.

As a model reaction, we studied the electrooxidation of 2,3-butanediol on the low-index Pt(111), Pt(100) and Pt(110) surfaces in an acidic environment. We modified the surfaces with the IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2C1Im][OTf]) dissolved in the aqueous electrolyte. The reaction mechanisms on the different surfaces were studied by electrochemical infrared reflection absorption spectroscopy (EC-IRRAS) in combination with density functional theory (DFT).

The oxidation of 2,3-butanediol is highly structure dependent. On Pt(111), the oxidation occurs in two steps, forming acetoin as an intermediate and diacetyl as the final product. On Pt(110), only the first oxidation step takes place, forming acetoin as the final product. No adsorbed COads is formed during the reaction on either surface. On Pt(100), the final product is acetoin. However, adsorbed COads is formed, which acts as a catalyst poison. On Pt(111), already low concentrations of IL (0.001 M) shift the selectivity towards acetoin from 19% to 56%.[1] We propose that the potential dependent co-adsorption of the [OTf]- anion suppresses the adsorption of OH species required for oxidation in the potential region of the second oxidation step. On the Pt(100) surface, IL suppresses the formation of poisoning COads while the surface remains active for the target reaction.[2] Our results demonstrate the potential of ILs to control selectivity in electrocatalytic reactions.

[1] T. Yang, J. Yang, X. Deng, E. Franz, L. Fromm, N. Taccardi, Z. Liu, A. Görling, P. Wasserscheid, O. Brummel, J. Libuda, Angewandte Chemie International Edition
2022, 61, e202202957.

[2] J. Yang, E. Franz, L. Fromm, N. Taccardi, A. Görling, P. Wasserscheid, O. Brummel, J. Libuda, in preparation.
(Invited) Effects of Nano-Structure on the Kinetics of the Oxygen Reduction over N-Doped Carbon
Authors: Nabae Yuta
Published: February 2024

Nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) have great potential to substitute precious metal alloy catalysts for the electrochemical synthesis of H2O2 based on a fuel cell setup. Consequently, obtaining a kinetic understanding of nitrogen-doped carbon catalysts in acidic media is essential. Our research group has established a mathematically and experimentally modified RRDE approach to calculate the corresponding kinetic rate constants, which significantly reduced the calculation noise by avoiding a rotation speed study. Furthermore, the overestimation of the 4-e reduction process, which is related to the (2+2)-e pathway (k
2 + k
3) in the catalyst layer matrix, was corrected by studying the effect of the catalyst loading density. The established method was successfully applied to the ORR over Fe/N/C and N/C catalysts in acidic and alkaline media (Table 1). The results indicate that Fe/N/C catalysts follow mixed reduction pathways of 4-e and 2-e reductions in acidic media, and a pure 4-e reduction pathway in alkaline media, whereas the N/C catalyst exhibits a pure 2-e reduction pathway in acidic media, and mixed reduction pathways of 4-e and 2-e reductions in basic media.

Among the catalysts mentioned above, the N/C catalyst is the most promising for the electrochemical synthesis. To minimizing the effect of k
3, introducing mesoporous structure would be beneficial, because the H2O2 produced by k
2 can be smoothly eliminated without the further reduction to H2O by k
3 (Figure 1). In this context, we have synthesized a N-doped mesoporous carbon by pyrolyzing a N and C source in a mesoporous silica, KIT-6, as a hard-template. This synthesis resulted in a mesoporous carbon with a gyroid structure. The electrochemical study has revealed that this catalyst exhibits a quite high selectivity over 90 % to the 2-e reduction in acidic media.

Figure 1
(Invited) Research Progress of Electrocatalyst and MEA of PEM Fuel Cell and Water Electrolyser
Authors: Shao Zhigang
Published: February 2024

The successful commercialization of PEM fuel cell and water electrolyser is determined by the performance, durability, and cost of electrocatalyst and MEA. Compared with conventional electrodes, nanoarray electrodes feature enhanced mass transport thanks to continuous proton and electron transport channels. Herein, a series of nanoarray electrodes were developed directly as the electrodes for PEM fuel cells and water electrolysers. A catalyst layer based on porous Pt−Ni nanobelt arrays were prepared by the magnetron sputtering of Pt and Ni on a sacrificed template, followed by acid etching. The porous Pt−Ni nanobelt arrays-based catalyst layer exhibited superior fuel cell performance in H2/air conditions and RH 40%. The performance of the MEA with porous Pt−Ni nanobelt arrays reached 366.6 and 597.6 mW cm−2 with Pt loadings of 36.5 μg cm−2/36.5 μg cm−2 and 108.9 μg cm−2/108.9 μg cm−2 at the cathode/anode, respectively. Besides, a WO3 nanoarray electrode with a heterogeneous IrRu coating was prepared via a facile electrodeposition approach. The obtained IrRu@WO3 electrode exhibits a competitive overpotential of 245 mV at 10 mA cm−2. A single cell enables a current density of 4.5 A cm−2 at 2.13 V with the Ir loading of 115 mg cm−2. The nanoarray structure remains unchanged in a single-cell during a 500-h stability test. In sum, these work highlights a new approach to enhance the performance and durability for PEM fuel cells and water electrolysers.
(Invited) Advanced Photoelectron Spectroscopy on Battery Materials: Lessons Learnt on Silicon- Containing Electrodes
Authors: Jeschull Fabian , He Jiarong , Ghamlouche Ahmad , Gehrlein Lydia , Maibach Julia
Published: February 2024

While Silicon (Si) is being incorporated more and more as an active material in commercial lithium-ion batteries, it is still a topic of intense research and the motivation for these research efforts remains unchanged: Silicon’s large volume expansion during cycling leads rapid capacity fading largely associated with changes in the Si surface chemistry and unstable solid electrolyte interphase (SEI). Using advanced photoelectron spectroscopy (PES) characterization, we have investigated crucial interfaces on Si model systems and Si-containing negative electrodes for Li-ion batteries. Here, we focus on two approaches to influence the SEI composition intrinsically: Binders and electrolytes.

Starting with pristine Si powders, we studied the effect of carboxylic acids as electrode slurry additives on the Si surface chemistry before and after electrochemical cycling [1] using synchrotron PES depth profiling. Further, we used photoelectron spectroscopy to confirm cross-linking in poly-acrylic acid-based binder for Si electrodes and showed that the cross-linking agent pentaerythritol had no negative effect on the SEI thus attributing improved cycling performance to increased binder cross-linking [2].

In silicon/graphite negative electrodes, we used PES to elucidate the influence of fluoroethylene carbonate (FEC) on the degradation phenomena in electrodes with varying silicon content [3]. Finally, photoelectron spectroscopy provided insights into what happens to the SEI on Si-containing electrodes if we replace the classical electrolyte solvent ethylene carbonate with either FEC or glyoxylic acetal-based alternatives [4, 5].

[1] F. Jeschull, H.Q. Pham, A. Ghamlouche, P.K. Thakur, S. Trabesinger, J. Maibach, J. Phys.
Energy
2023, 5 (2), 025002. https://doi.org/10.1088/2515-7655/acbbee.

[2] J. He, C. Das, F. Yang, J. Maibach, Electrochimica Acta
2022, 411, 140038. https://doi.org/10.1016/j.electacta.2022.140038.

[3] A. Ghamlouche, M. Müller, F. Jeschull, J. Maibach, J. Electrochem.
Soc.
2022. https://doi.org/10.1149/1945-7111/ac4cd3.

[4] L. Gehrlein, C. Njel, F. Jeschull, J. Maibach, ACS Appl.
Energy Mater.
2022, 5 (9), 10710–10720. https://doi.org/10.1021/acsaem.2c01454.

[5] L. Gehrlein, C. Leibing, K. Pfeifer, F. Jeschull, A. Balducci, J. Maibach, Electrochimica Acta
2022, 140642–140642. https://doi.org/10.1016/j.electacta.2022.140642.
In Situ Raman Spectroelectrochemical Investigation of Composite Si Nanoparticle-Based Anode for Li-Ion Batteries during (de)Lithiation Process
Authors: Vlčková Zuzana , Jindra Martin , Soukupová Gabriela , Lapka Tomáš , Sonia Farjana , Müller Martin , Červenka Jiří , Fejfar Antonín , Hassouna Fatima , Frank Otakar
Published: February 2024

The key degradation processes in the composite anode for the Li-ion batteries (LIBs) prepared using Si nanoparticles (SiNPs) with two types of a conductive carbon-based matrix [carbon black (CB) and carbonized polypyrrole (CPPy)] were studied by in situ Raman spectroelectrochemistry (SEC). This combined technique provides non-destructive and real-time monitoring of the chemical and structural changes that occur during battery operation. These processes, such as the crystal lattice changes (expansion/contraction) and possible degradation/amorphization of silicon, the solid electrolyte interphase (SEI) layer formation on the electrode surface during the charge/discharge reactions, and the stability of the carbon-based matrix, significantly affect the performance of Si-based LIBs in many ways. Especially, the large silicon volume expansion (more than 300%) and associated stress cause mechanical instability resulting in rapid capacity fading. To overcome this challenge, various strategies have been proposed, including the use of CPPy as a conductive matrix to prevent large volumetric changes and also provide a pathway for electron transfer.

This study investigates the initial degradation mechanisms such as the formation of the SEI layer, as well as possible structural changes caused by the volume expansion of SiNPs. The shift of the first-order Raman peak of Si at 521 cm-1 which is assigned to crystalline silicon is related to the stress evolution in nanoparticles caused by the (de)lithiation-induced stress (tensile-to-compressive transition) in SiNPs and the native oxide on their surface. Additionally, the detailed in situ Raman measurement of the first lithiation cycle allowed us to detect the decomposition of the electrolyte (LiPF6 in EC/DMC) close to the Si surface which is associated with SEI layer formation. A decrease in the intensity of the Raman vibrational modes (700–1050 cm−1) of EC/DMC corresponding to the decomposition of the electrolyte was observed at reduction potentials of 0.8 V and 0.3 V vs. Li/Li+ corresponding to the same potentials determined by cyclic voltammetry. The Si-based anode containing CPPy as active carbon showed better electrochemical properties (higher charge/discharge capacity and cycling stability) in Li-ion batteries than Si/CB despite the higher conductivity of the latter. The correlation between the chemical structure of the active carbon and the electrochemical properties of the resulting Si-based anodes will be discussed.

Acknowledgment: This work was supported by the Czech National Foundation, Project No. 21–09830S.
(Keynote) Development of Advanced High Surface Area Metal Oxide Aerogels for Oxygen Evolution Reaction Electrocatalysis
Authors: Elbaz Lior
Published: February 2024

The growing demand to shift energy production to sustainable sources poses some serious challenges. One of the biggest are the intermittent energy (wind and sun). To mitigate this issue, there is a critical need for large energy storage technologies, to store excess energy during the peak hours and carry it over for the rest of the day, weeks, and seasons. The best way to do so is through the Hydrogen Economy. At the heart of this scheme is green hydrogen production using water electrolysis.

There are two distinct chemical reactions that take place in water electrolyzers: the cathodic hydrogen evolution reaction (HER), and the anodic oxygen evolution reaction (OER). Both reaction require catalysts to execute at high rates, and while the HER is considered to be relatively facile and takes place at low overpotentials, the OER requires relatively high overpotentials and high loadings of precious metal catalysts. It is considered the bottleneck reaction. The OER is a four electrons oxidation reaction per generated O2 molecule and proceeds in four distinct reaction steps. This leads to a very sluggish reaction kinetics and high overpotentials to reach viable current densities.

In recent years, more and more non-precious metal OER catalyst have been developed. Most notably is the family of mixed nickel-iron oxyhydroxides (NiFeOOH), which are relatively cheap, selective and efficient catalysts in alkaline media, and their performance has been increased by optimizing the Ni:Fe ratio. One challenge that still remains is to increase the NiFeOOH surface area, and by that the electrochemically active site density (EASD).

In this regard, one class of materials that has been attracting the attention of materials’ scientists in recent years are aerogels. Aerogels can be made from many different materials, such as silicates, carbons, metal organic materials, bio-inspired molecules, metals, and metal oxides. They consist of distinct units which form a porous 3D covalent framework (COF). Because of their diversity, aerogels have many different applications, e.g. as insulators, sensors, or catalysts.

In this talk we will report the synthesis of NixFeyMzOOH aerogels, with a modified easy synthetic method via an epoxide route. These aerogels show much higher utilization of the material and overall increase in mass activity when catalyzing the OER when compared to other NiFeOOH derived materials. They were tested for their OER electrocatalytic activity and to the best of our knowledge these are the first aerogel materials that propagate OER themselves, rather than being used merely as support material for OER catalysts. The catalytic activity depends largely on the Ni:Fe ratio and not the surface area, which can lead to mass transport limitations when too high, showing an optimum for the ratio and the surface area.
Hollow TiO2 Supports for Enhanced Acidic Oxygen Evolution Activity
Authors: King Laurie , Belami Debora , Jonnalagadda Umesh , Fan Wenhao , Kwan James , Regmi Yagya
Published: February 2024

The usage of scarce and expensive iridium as a catalyst for the acidic oxygen evolution reaction (OER) represents a significant barrier to up-scaling the deployment of proton exchange membrane water electrolysers (PEM-WEs). Accordingly, strategies such as nanostructuring catalysts to increase the electrochemical surface area (e.g. nanoparticles, single-atom catalysts, nanoclusters) as well as investigating mixed metal alloys and oxides (e.g. perovskites, pyrochlores) have been developed with promising half-cell performances. One further approach that has recently gained attention is the deployment of catalyst-supports whereby a high surface area support is used to scaffold the dispersed iridium catalyst.1 Analogous to the selection of a catalyst, the catalyst support must withstand the highly corrosive and oxidising conditions of a PEM-WE anode. Thus, metal oxides such as titanium dioxide are commonly deployed as catalyst-supports for acidic OER. The catalyst-support moiety must also be sufficiently conductive when integrated into the PEM-WE catalyst layers. Otherwise, the cell voltages required to generate sufficient activity will render the device impractical. Accordingly, strategies such as doping, or the addition of conductive layers between the catalyst and support have been investigated.2

In this study we investigate a unique support morphology that affords promising OER activity and stability in acidic electrolyte with high iridium mass activities. Specifically, we deploy a hollow TiO2 catalyst support,3 coated with a Au/Pd interlayer to provide electrical conductivity. The OER activity and stability is initially screened in a rotating disk electrode (RDE) configuration as a function of thermal treatments (reducing vs oxidising) as well as with at various Au/Pd (1 – 5 wt%) and Ir loadings (35 – 50 wt%). Our highest performing catalyst have a mass activity of around 480 A/gIr at 1.60 V vs RHE. The catalysts are subsequently investigated in a membrane electrode assembly (MEA) and subject to 10k accelerated stress test stability measurements. To understand the role of the support morphology, Au/Pd interlayer and iridium loadings on electrochemical performance, we also characterise the synthesised catalysts by (scanning) transmission electron microscopy (STEM/TEM), X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS) and electrical conductivity measurements. Collectively, we report the critical role of the Au/Pd interlayer to enable such high electrochemical performance. We also show that the hollow structure of the TiO2 support may be enhancing mass transport in the catalyst layers.

References

1 A. S. Pushkarev, I. V Pushkareva and D. G. Bessarabov, Energy & Fuels, 2022, 36, 6631–6625.

2 Y. N. Regmi, E. Tzanetopoulos, G. Zeng, X. Peng, D. I. Kushner, T. A. Kistler, L. A. King and N. Danilovic, ACS Catal., 2020, 10, 13125–13135.

3 U. S. Jonnalagadda, X. Su and J. J. Kwan, Ultrason. Sonochem., 2021, 73, 105530.
Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis
Authors: Heymann Lisa , Weber Moritz L , Wohlgemuth Marcus , Risch Marcel , Dittmann Regina , Baeumer Christoph , Gunkel Felix
Published: February 2024

Testing single crystalline epitaxial thin films as model systems for metal oxide electrocatalysts in the oxygen evolution reaction (OER) enables differentiating the OER descriptors such as crystal facet orientation, surface chemical composition, electronic structure and band bending at the interface to the electrolyte [1,2,3]. We designed single crystalline perovskite oxide bilayer structures to systematically tune the surface electronic structure and the band bending at the electrode/electrolyte interface to understand their role in the OER.

The Co−O covalency in perovskite oxide cobaltites such as La1
−
x SrxCoO3 is believed to impact the electrocatalytic activity during the OER. Additionally, space charge layers through band bending at the interface to the electrolyte may affect the electron transfer into the electrode, complicating the analysis and identification of true OER activity descriptors. Here, we separate the influence of covalency and band bending in hybrid epitaxial bilayer structures of highly OER-active La0.6Sr0.4CoO3 and undoped and less-active LaCoO3. Ultrathin LaCoO3 capping layers of 2−8 unit cells on La0.6Sr0.4CoO3 show intermediate OER activity between La0.6Sr0.4CoO3 and LaCoO3 evidently caused by the increased surface Co−O covalency compared to single LaCoO3 as detected by X-ray photoelectron spectroscopy. A Mott−Schottky analysis revealed low flat band potentials for different LaCoO3 capping layer thicknesses, indicating that no limiting extended space charge layer exists under OER conditions as all catalyst bilayer films exhibited hole accumulation at the surface [1].

The combined X-ray photoelectron spectroscopy and Mott−Schottky analysis of atomically defined bilayer structures thus enables us to differentiate between the influence of the covalency and intrinsic space charge layers, which are indistinguishable in a single physical or electrochemical characterization. Our results emphasize the prominent role of transition metal oxygen covalency in perovskite electrocatalysts and introduce a bilayer approach to fine-tune the surface electronic structure [1].

[1] L. Heymann, M. L. Weber, M. Wohlgemuth, M. Risch, R. Dittmann, C. Baeumer, F. Gunkel (2022) Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis, ACS Appl. Mater. Interfaces

[2] M. Wohlgemuth, M. L. Weber, L. Heymann, C. Baeumer, F. Gunkel (2022) Activity-Stability Relationships in Oxide Electrocatalysts for Water Electrolysis, Front. Chem.

[3] M. L. Weber, G. Lole, A. Kormanyos, A. Schwiers, L. Heymann, F. D. Speck, T. Meyer, R. Dittmann, S. Cherevko, C. Jooss, C. Baeumer, F. Gunkel, (2022) Atomistic Insights into Activation and Degradation of La0.6Sr0.4CoO3-δ Electrocatalysts under Oxygen Evolution Conditions

Figure 1