bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing the Surface Properties of Nanoporous Biopolymer Materials from Ionic-Based Natural Fiber Welding
Authors: Cho Whirang , Larm Nathaniel E. , Stachurski Christopher D. , Durkin David P. , Trulove Paul C.
Published: December 2024

Natural fiber welding (NFW) has been widely used for the controlled partial dissolution of biopolymer textiles in ionic liquids (ILs) to regenerate surface morphologies with enhanced physical properties. Our group recently demonstrated that the solvation of cellulose by the welding IL results in the generation of a latent nanoporous biopolymer domain via an open-close cycling mechanism (i.e., the porous structure can be expressed or collapsed through solvent treatment). Surface thermodynamics profoundly impact the molecular interactions that provide important metrics for interfacial behaviors, such as adhesion, cohesion, and wettability. Thus, surface energy controls the nature of chemical interactions at the surface of a material, determining hydrophobicity, reactivity, and polarity. In this study, surface energy and Lewis acid-base parameters are measured by inverse gas chromatography (iGC), and the resulting data is used to establish trends in hydrogen bond donating/accepting ability as well as hydrophilicity based on solvent exchange from a polar rinse solvent (i.e., water) to a nonpolar solvent (i.e., cyclohexane). The surface thermodynamics information obtained from iGC will complement BET analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS) to provide a better understanding of the role of solvent properties on the morphologies of regenerated biopolymer nanoporous xerogels. We will discuss the impact of solvent identity on surface area, pore distribution, and surface energy to elucidate the interplay between porous morphologies and surface characteristics.
Finding Diffusivity and Solubility of Impurities inside ILs By MD
Authors: Aryal Dipak , Rotondaro Antonio , Nakano Takeo , Morimoto Tamotsu
Published: December 2024

Ionic liquids (ILs) are promising candidates for use in the semiconductor industry because of their unique and tunable physicochemical properties. They are a novel class of salts with desirable features such as being in liquid phase at room temperature, nonflammability, high ionic conductivity, high thermal stability, and low to negligible vapor pressures. Their physical, chemical, solubility, transport, and solvation properties can be tuned by altering the cations or anions to tailor for applications in the semiconductor industry, including the process of liquid/gas separations, extraction of impurities, and cleaning under vacuum. Selecting suitable ILs to enhance the efficiency of the target semiconductor processes and tools is crucial.

One possible application is to use ILs as a barrier or protective liquid film that does not evaporate in low-pressure conditions. For this application, we need a better understanding of the molecular scale of the behavior of the ILs at different temperature ranges. To develop such a new process, the knowledge of absorbing/desorbing impurities (such as O2, CO2, and H2O, including their mixtures and other organic materials) in the ILs and their transport (diffusion coefficients) properties inside the ILs at different temperatures is essential from the surface protection film point of view. This work seeks to answer these essential questions at the nanometer scale by showing the results from molecular dynamics (MD) simulations of the diffusivity and solubility of impurities inside ILs. Examples of MD simulation models for this study are shown in Figure 1, where impurities with the same concentration are placed on both sides of ILs, and the transport behavior of impurities inside ILs is extracted. From these nanoscale results, we can better understand and predict the diffusivity and solubility of impurities inside ILs and find the conditions at which impurities can be removed from ILs for recycling purposes.

Figure 1
Simulation of Voltammetric Measurements of Uranium Electrodeposition in Molten LiCl-KCl Eutectic
Authors: Stoddard Michael , Mejia Carlos , Rappleye Devin
Published: December 2024

The electrochemical behavior of uranium in high-temperature molten salts is central to the development of advanced nuclear reactors (e.g., molten salt reactors) and reprocessing technologies (e.g., pyroprocessing). Numerous studies have been performed on uranium in molten salts, especially LiCl-KCl eutectic. However, many studies rely on models, such as Berzins-Delahay model, which assume mass transfer by diffusion only and a pure deposit (i.e., unit activity for the reduced species).1 In many situations, these assumptions may not be appropriate for analyzing electrochemical data in molten salts and may introduce significant error in the estimation of properties, such as diffusion coefficients. For example, a foreign substrate, such as tungsten or molybdenum, is often used as the working electrode in electroreduction of uranium ions to metal in molten salts. Hence, nucleation effects and incomplete coverage of the WE can affect measurements, especially at dilute concentrations. Additionally, macro electrodes are often used in molten salts due to a lack of compatible insulating material for construction of microelectrodes. This results in large currents which can introduce significant ohmic losses despite the relatively low ohmic resistance of molten salts. Furthermore, additional effects, such as migration and natural convection, can significantly impact electrochemical measurements in molten salts containing a heavy analyte, such as uranium ions.

To address these challenges, a model was developed specifically for electrodeposition in molten salts based on the Nernst-Plank equation, Nernst equation, adsorption isotherms, and activity models. The initial iteration of the model has been designed to account for the combined effects of diffusion, migration, ohmic resistance, deposition onto a foreign substrate, and activity of non-ideal solutions. The significance of each effect and combination of effects has been examined for linear sweep voltammetry at various uranium ion concentrations and scan rates. Furthermore, the model has been validated against uranium electrodeposition measurements on a tungsten WE in molten LiCl-KCl eutectic.

1. T. Berzins and P. Delahay, J. Am. Chem. Soc., 75, 555–559 (1953) http://dx.doi.org/10.1021/ja01099a013.
Area Selective Atomic Layer Deposition for Spatial Control of Reaction Selectivity on Modelphotocatalysts
Authors: Stinson William D. H. , McNeary W. Wilson , Zang Wenjie , Pan Xiaoqing , Hurst Katherine , Esposito Daniel V.
Published: December 2024

Photocatalytic water splitting is one promising route to reducing the cost of H2 production to industrially relevant levels. However, these systems are currently limited in their solar-to-hydrogen efficiency requiring further development in designing highly active and selective reaction sites. Reverse reactions, such as hydrogen oxidation or oxygen reduction, can greatly reduce overall system efficiency and are exacerbated by the close proximity of neighboring particles, which creates locally high concentrations of reactants. Metal oxide coatings have previously been used to selectively block undesired reactants from reaching the active sites, but can be limited in their ability to allow two different desired half reactions to occur as required for photocatalysts. In this work, we target selectively-deposited ALD of oxide films (e.g., TiO2 and SiO2) onto metallic co-catalysts for enhancing reaction selectivity while maintaining a high overall activity. Pt and Au were used an exemplary reduction and oxidation co-catalysts sites, where Au was deactivated towards ALD growth through self-assembled thiol monolayers while TiOx coated Pt suppressed Fe(II) redox reactions while maintaining the hydrogen evolution reaction (HER). The efficacy of the selective ALD growth was assessed through ellipsometry and X-ray photoelectron spectroscopy (XPS), while reaction selectivity was assessed through cyclic voltammetry. A planar photocatalyst model of patterned interdigitated arrays of Au and Pt was developed to further assess the selective ALD on the micron scale. Patterned electrodes were evaluated through cross-sectional scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS) and XPS, while reaction selectivity towards the HER over Fe(II) reduction was estimated using scanning electrochemical microscopy (SECM). Finally, interdigitated electrodes were used to simulate the effect of neighboring particle photocatalysts, where selectively deposited TiOx showed a significant reduction in reverse reactions over the uncoated samples.
(Invited) Extending the Success of Halide Perovskites to Photoelectrochemical and Photocatalytic Solar Fuel Production
Authors: Eslava Salvador
Published: December 2024

To address the pressing global energy demands with clean and sustainable methods, solar-powered photoelectrochemical and photocatalytic transformations of water and carbon dioxide present viable solutions. Achieving this requires the development of cost-effective photoelectrodes and photocatalysts capable of efficiently harnessing solar light and promoting charge transfer to drive water and carbon dioxide reactions. In this presentation, I will outline the advances my team has made in the field, focusing on novel halide perovskites like CsPbBr3, Cs2AgBiBr3, and Cs3Bi2Br9 and bulk heterojunctions of organic semiconductors. These materials exhibit high solar light absorption and outstanding optoelectronic properties, making them excellent candidates for photoelectrochemical and photocatalytic uses. We have developed innovative approaches to enhance their stability in aqueous environments, such as encapsulating halide perovskites and organic bulk heterojunctions within carbon layers modified with Ni nanopyramids and NiFeOOH, a water-oxidation catalyst. This approach exploits different carbon allotropes, from mesoporous carbon to graphite, glassy carbon and boron-doped diamond, in order of chemical and mechanical stability. The use of layers and sheets of these carbon allotropes has led to the creation of photoanodes with low onset potentials and high photocurrents, efficiently translating excellent photocurrents and photovoltages from solar cells to photoelectrodes. For example, organic bulk heterojunction devices result in 25 mA/cm2 photocurrents in three-electrode systems and unassisted 5% solar to hydrogen in two-electrode systems Our approaches significantly extend the lifespan of photoanodes, maintaining for example a projected operation of months with CsPbBr3. In the field of photocatalysts, we have employed mechanochemical synthesis and antisolvent crystallization to create innovative composites like CsPbBr3/Cu-RGO, Cs2AgBiBr3/Cu-RGO, Cs2AgBiBr3/bismuthene, and Cs3Bi2Br9/RGO/g-C3N4, demonstrating efficient activity in converting CO2 into CO and CH4. Through thorough material characterization, we have shed light on their structural and charge-transfer properties, laying a solid foundation for their ongoing development and practical application.

Daboczi, M.; Eisner, F.; Luke, J.; Yuan, S.W.; Al Lawati, N.; Müller, J.S.; Kim, J.S. Nelson, J.; Eslava, S. under review

Zhu, Daboczi, Chen, Xuan, Liu and Eslava, Nat. Commun. 2024, 2791.

Daboczi, M.; Cui, J.; Temerov, F.; Eslava, S. Adv. Mater. 2023, 2304350

Baghdadi, Y.; Temerov, F.; Cui, J. Daboczi, M.; Rattner, E.; Sena, M.S.; Eslava, S. Chem. Mater. 2023, 35, 20, 8607

Sena, M.S.; Cui, J.; Baghdadi, Y.; Rattner, E.; Daboczi, M.; Lopes-Moriyama, A.L.; dos Santos, A.G.; Eslava, S. ACS Appl. Energy Mater. 2023, 6, 10193.

Kumar, S.; Hassan, I.; Regue, M.; Gonzalez-Carrero, S.; Rattner, E.; Isaacs, M.A.; Eslava, S. J. Mater. Chem. A 2021, 9, 12179
(Invited) Advancing Photocatalysis through Model Systems and Single Particle Measurements
Authors: Esposito Daniel V. , Stinson William D. H. , McNeary W. Wilson , Dunn Kevin , Hurst Katherine
Published: December 2024

Photocatalytic water splitting using photocatalyst particles holds great promise for achieving efficient and cost effective production of renewable hydrogen (H2). However, demonstrations of photocatalytic water splitting have generally been plagued by low solar-to-hydrogen conversion efficiencies. Gaining deeper insights into loss mechanisms and interactions between different particles and components is essential for enabling rational design of ensembles of high performance photocatalysts for which these losses are minimized. Towards this end, our team has taken a two pronged approach that relies on the development and use of (i) model systems and (ii) single particle measurements. The first approach relies on the use and development of a planar analog photocatalyst for which all parts of a multi-component photocatalyst (e.g. light absorber, co-catalysts, selective coatings) can be integrated with excellent control over feature size, positioning, and density. This planar analog platform also allows for easier access of advanced analytical tools like scanning electrochemical microscopy, which can be used to directly probe spatial variation in performance and better understand interactions between components as a function of proximity and operating conditions. In this talk, I will describe how this approach can be especially useful for quantifying losses associated with undesired “back reactions” occurring at neighboring active sites, which can be a primary loss mechanism in photocatalyst systems. After describing efforts relating to planar analog photocatalysts, I will also present results from our studies of individual photocatalyst particles that rely on local optical and electrochemical probes to measure the relative performance of individual particles in the presence and absence of neighboring particles.
(Invited) Synergistic Effects between Surface Charge and Catalytic Site in Photoelectrochemical Water Splitting Reactions
Authors: Wang Dunwei
Published: December 2024

Photoelectrochemical water splitting promising a practical route toward solar energy harvesting. The successful completion of this reaction requires coordination between light absorber and catalysis. It is often presumed that catalysis is a limiting factor in this chain of events, whereas little attention has been paid to the synergistic effect between the charge concentration and catalytic site density. In this talk, we will examine the interplays between these two key factors. We will start with a discussion on recent literature reports that point to the importance of coordination between these two factors and then discuss how these two variables can be controlled separately. We will move on to present detailed studies on water oxidation model reactions, which represent a bottleneck in the solar fuel synthesis efforts. We show that at high surface charge concentrations, each catalytic site acts independently, whereas there are clear cooperative behaviors among catalytic sites at low surface charge concentrations. It is implied that having an overload of co-catalysts is not always desired. The results are expected to serve as a guideline for future efforts aimed at optimizing photocatalyst designs.
Data-Driven Analysis of Contributing Factors in Spectra Toward Quantitative Prediction of Photocatalytic Activity of BaTaO₂N
Authors: Yamada Musashi , Yamada Tetsuya , Yanagisawa Kazumichi , Tipplook Mongkol , Hayashi Fumitaka , Teshima Katsuya
Published: December 2024

Photocatalytic hydrogen production via water splitting has attracted attention as an energy infrastructure independent of fossil resources. However, it has not yet reached the practical energy conversion efficiency level (5%), necessitating the enhancement of photocatalyst materials. Various crystal characteristics such as crystal shape, surface state, and lattice defects are known to be influencing factors on the performance of photocatalysts. However, their quantitative correlation and synergistic effects of each factor on performance are unclear. Understanding the quantitative correlation of crystal properties with photocatalytic activity would give effective crystal design for improvement. In this study, we aimed to extract crystallographic properties and understand their correlation with photocatalytic water splitting by multivariate analysis. BaTaO2N (BTON), which responds to visible light, was selected as a model material for photocatalysis.

First, internal crystal information was collected from X-ray diffraction (XRD) patterns and Ultraviolet-Visible (UV-Vis) absorption spectra. Interpretable feature values, such as intensity ratio and full width at half maximum at the diffraction peak, impurity, absorption edge wavelength and its area were automatically extracted using Python. The factors contributing to water splitting were then identified by using LASSO regression. These feature values were used to depict a two-dimensional dimension reduction diagram (t-SNE diagram), which describe photocatalytic activity as color map. The t-SNE diagram confirmed the clustering of data with similar water splitting activity, indicating that this diagram can be used as an effective guide to explore the crystal properties with high photocatalytic activity. Next, scanning electron microscopy (SEM) was analyzed to extract additional feature values. Image analysis was carried out for the comprehensive extraction of crystal surface information. Gray-Level Co-occurrence Matrix (GLCM) texture analysis was an effective method for detecting boundary parts, thus used to extract abstract crystal surface information. In addition, Variational Autoencoder (VAE) was used to extract specific crystal surfaces. The extracted feature values can contain information about crystal surface structures such as crystal morphology, particle agglomeration, and co-catalyst support state. Correlation analysis between these feature values and photocatalytic activity is now underway and will be reported in the presentation.

Acknowledgement

This work was partly supported by the Strategic Innovation Program (SIP) of the Cabinet Office, the NEDO Green Innovation fund projects, and collaborative research with companies.
Construction of ITO Nanoparticle Immobilized Substrates and Evaluation of Their Photocurrent Responses
Authors: Kanaizuka Katsuhiko , Yamaguchi Mei
Published: December 2024

Near-infrared (NIR) light can be used in a variety of fields, including energy conversion devices and medicines. However, there are only a limited number of compounds with NIR absorption, and research into their effective use remains unexplored. Previous research in our laboratory has reported the enhancement of visible light absorption in devices based on the combination of metal nanoparticles and functional molecules. In this study, we applied the system of the previous study to investigate the fabrication conditions of composite substrates of indium cubic tin oxide nanoparticles (ITO NPs), which have localized surface plasmon resonance (LSPR) absorption in the NIR region, and silicon naphthalocyanine derivative (SiNPc), which absorbs NIR light, and the photocurrent of the fabricated substrates.

ITO NPs were synthesised by a solvothermal method using ethylene glycol. SiNPc was synthesised by mixing SiNPcCl2 with 1-octanol. The conductive substrates were sonically cleaned, ozonated and then surface treated by the immersion in a 3-Aminopropyltrimethoxysilane (3-APTMS) solution. ITO NPs immobilized substrates were constructed by spin-coating method. This substrate was immersed in a SiNPc solution to construct the conductive substrate/3-APTMS/ITO NPs/SiNPc composite substrate.

The synthesized nanoparticles were confirmed to be cubic ITO NPs with high crystallinity and approximately 30 nm per side from XRD and TEM images. The UV-Vis-NIR spectrum of the fabricated substrates showed the absorption of the soret band of SiNPc at 340 nm and the LSPR absorption of ITO NPs in the NIR region, indicating that the conductive substrate/3-APTMS/ITO NPs/SiNPc composite substrate was fabricated. Photocurrent measurements were carried out using NIR light, and the cathode current was observed.
Monolithic Lead Halide Perovskite Based Photoanode with 9.16% Applied Bias Photon-to-Current Efficiency
Authors: Kim Tae Gyun , Park Jong Hyeok
Published: December 2024

The quest for sustainable hydrogen production through solar energy conversion has directed attention towards photoelectrochemical (PEC) cell water splitting, a promising avenue for hydrogen (H₂) generation. Traditional metal-oxide-based photoelectrodes such as TiO2 and WO3, despite their extensive study, fail to absorb visible light effectively and exhibit poor charge transport properties. In contrast, lead halide perovskites (LHPs) emerge as a superior alternative, endowed with exceptional optoelectronic properties that enhance the solar spectrum photoresponse, critical for the efficient utilization of solar energy in hydrogen production.

This study focused on optimizing the photoanode materials by improving the intrinsic properties of LHPs through bandgap tuning and enhanced charge transfer to the oxygen evolution reaction (OER) catalyst. However, the operational stability of LHPs in PEC applications poses a formidable challenge, primarily due to vulnerability to moisture-induced degradation.

Addressing the stability concerns, some researches about application of ultrathin Ni surface layers and the use of low-melting-point field metals for protective encapsulation are reported. However, these methods have shown limited success in preventing moisture-induced degradation. In response, this work proposes the innovative use of conductive carbon poweder (CCP) as a superior alternative for enhancing electrical connectivity and stability between LHP solar cells and the OER catalyst.

Our findings reveal that CCP's superior conductivity facilitates efficient charge transfer from LHP-based solar cells to OER catalysts, maintaining negligible current and voltage loss. To optimize the LHP photoanode's performance, we focused on enhancing the individual efficiencies and stabilities of the PSC and OER catalyst components. For the PSC, we improved stability by integrating a smaller cation (methylammonium, MA) into the FAPbI3 (formamidinium, FA) lattice, thereby stabilizing the α-phase and enhancing hydrogen bonding. This modification was substantiated through various spectroscopic and X-ray diffraction. Meanwhile, the OER catalyst's efficiency was amplified by employing a 3D-structured NiFe on an Ni foil substrate, improving catalytic activity and stability through enhanced hole mobility and increased electrochemically active surface area.

The integrated LHP photoanode demonstrated a notable onset potential of 0.56 V and a peak photocurrent density of 24.26 mA/cm² at 1.23 V vs RHE, achieving a 9.16% applied bias photon-to-current efficiency and sustained performance over 48 hours in a pH 14 aqueous solution under simulated solar illumination. This performance is attributed to the synergistic effect of the optimized PSC and OER catalyst, facilitated by CCP's efficient electrical connectivity.
Cu2o@Cu2-Xs Core@Shell Nanocrystals: Morphologic Effect on Photocatalytic Hydrogen Production
Authors: Yang Shan-Jen , Pu Ying-Chih , Hsu Yung-Jung
Published: December 2024

Cu2O nanocrystals (NCs) with different morphologies, including the cube (Cub), the octahedron (Oct), and the rhombic dodecahedron (Rd) were prepared by hydrothermal synthesis by adding different kinds of anions as adsorbents. Subsequently, Cu2O NCs were used as templates to prepare Cu2O@Cu2-xS core@shell nanocomposite structures with three morphologies by the anion exchange method. By employing time-resolution photoluminescence and ultraviolet photoelectron spectroscopy, the correlations among charge carrier dynamics, energy band structure and photocatalytic activity of Cu2O@Cu2-xS was analyzed. It was found that as the Cu2-xS shell reached a certain thickness, the photocatalytic hydrogen production rates of Cub-, Oct-, and Rd-Cu2O@Cu2-xS can respectively reach 167.50, 279.18, and 111.03 μmol g-1h-1. The highest photocatalytic activity of Oct-Cu2O@Cu2-xS corresponded well to the largest interfacial charge transfer rate constant observed from time-resolution photoluminescence analysis. The apparent quantum yield of hydrogen production was further measured, showing remarkable photoactivities across the visible to near infrared region for Oct-Cu2O@Cu2-xS. The findings of this study illustrate that Cu2O@Cu2-xS NCs hold promise as practical photocatalysts for solar fuels generation.
Sustainable Environmental Application of Au@SnO2 Core@Shell Nanocrystals
Authors: Chang Huai En , Hsu Yung-Jung
Published: December 2024

Finding adaptable catalysts to support long-term environmental cleaning has become a difficult but necessary research, especially in the post pandemic era. Core@shell nanocrystals, which are made of a semiconductor shell and a metal core, have attracted a lot of interest for their potential use in the bacterial disinfection and degradation of organic dyes. In this study, Au@SnO2 core@shell nanocrystals with tunable shell thicknesses were synthesized. Au@SnO2 can be used as photocatalysts in light conditions to inactivate E. coli and degrade organic dyes like rhodamine B (RhB). The investigation of carrier dynamics showed that the band alignment between Au and SnO2 produced effective charge separation, which improved the photocatalytic activity. On the other hand, Au@SnO2 possessed peroxidase mimics features, allowing for effectively disinfecting E. coli under dark conditions. Au@SnO2 exhibited sustained activity in E. coli disinfection under both irradiation and darkness conditions by combining the capability of photocatalytic functions with peroxidase mimics.
(Invited) Enhancing Efficiency, Stability and Versatility in Dye-Sensitized Photoelectrochemical Cells Via Spatially Controlled Cascade Charge Transfer
Authors: Kwon Tae_Hyuk
Published: December 2024

In this talk, I will present my group's recent research on dye-sensitized photoelectrochemical cells (DSPECs) aimed at green energy generation. Initially, I will introduce a molecular-design strategy that integrates both strong and relatively weak electronic couplings within a single sensitizer. This approach aims to facilitate vectorial electron transfer, mirroring the efficiency seen in natural photosystems, thereby improving light harvesting efficiency.

Next, to overcome the challenges of low photocurrent and limited stability in DSPECs, we develop a buried junction-type DSPEC. This utilizes a platinum-sputtered nickel foil to encapsulate both the dye-sensitized TiO2 layer and the redox mediator electrolyte. This design facilitates spatially controled cascade charge transfer, effective photoconversion, and water oxidation without the issues of current leakage. It also ensures high stability and versatility. By altering the photoredox electrolytes, we are able to reduce the onset potential required for water oxidation. Additionally, optimizing the kinetics of water oxidation is achieved by replacing the Ni catalyst with NiFe-LDH catalysts, which result in the photocurrent densities of 14.5 mA/cm² at 1.23 V versus the reversible hydrogen electrode.

Moreover, by substituting the Pt catalyst with oxygen-doped carbon nanotubes, we broaden the application of our buried-junction DSPECs to include the bias-free production of hydrogen peroxide with a solar-to-fuel efficiency (STF) of approximately 3.76%, and a high photostability.
(Invited) Photocatalytic Cleavage of C-C Bond in a Dye-Sensitized Photoelectrochemical Cell at Room Temperature
Authors: Leem Gyu
Published: December 2024

This talk will focus on photoelectrocatalytic selective cleavage of C-C/C-O bonds in biomacromolecules in the area of Carbon. Photocatalysis and electrocatalysis play a critical role in many organic reactions involving solar energy conversion, biomass, polymer degradation and environmental sustainability. Among reactions, oxidative cleavage of C–C/C-O linkages is a challenge for chemical transformations at room temperature. Controlling the extent of oxidation presents a key for the generation of targeted products. Here, we pioneer an aminoxyl radical-mediated (ARM) photoelectrocatalysis approach for the chemoselective oxidative cleavage reactions under ambient conditions by incorporating stable ARMs (or electron-proton transfer mediators) and heterogeneous photocatalysts. This study targets oxidative cleavage of C–C/C-O bonds in lignin, which is an aromatic polymer mainly bound via C–C/C-O bonds and the largest source of renewable aromatics, for the conversion of lignin into valuable low-molecular-weight chemicals in a dye-sensitized photoelectrochemical cell. The ARM catalyzed photoelectrocatalysis process can be applicable to oxidative cleavage reactions and expandable to a wide range of chemical transformations under aerobic mild conditions in synthetic organic chemistry and depolymerization.
(Invited) Engineering Microenvironments for Photo-Electrochemical Reduction of Carbon Dioxide
Authors: Kim Chanyeon , Bell Alexis T.
Published: December 2024

Due to the escalating crisis of global warming, carbon dioxide (CO2) conversion has garnered significant attention as a pivotal technology for sustainable energy and chemical processes. However, the challenge lies in its nature as a strong endothermic reaction with substantial activation energy, thus requiring extensive energy input. Therefore, integration with renewable energy sources becomes imperative. In this regard, Photo- and electrochemical CO2 reduction (CO2R) presents promising avenues for converting CO2 with water (H2O) using electricity derived from renewable sources, thereby producing various chemicals and fuels. However, the abundance of H2O in the catalytic microenvironment promotes the competing evolution of hydrogen (H2), leading to diminished energy efficiency and selectivity toward CO2R products. Additionally, another challenge is to selectively produce valuable multicarbon products (C2+ products), including C2H4, C2H5OH, and C3H7OH, which hold higher market value and greater market volume compared to single-carbon products (C1 products) like HCOOH, CO, and CH4. Among various CO2R catalysts, Copper (Cu)-based materials have emerged as prominent candidates due to their capability to yield C2+ products with considerable activity and selectivity. Recent studies suggest that catalytic microenvironments significantly influence C2+ production on Cu-based catalysts. Hence, this presentation aims to elucidate the impact of these microenvironments near Cu catalysts and explore how this knowledge can be effectively applied to design a photocathode for the photo-electrochemical reduction of CO2, thereby enhancing the production of C2+ products.
Coupling Time-Resolved Mass Spectrometry Techniques to Unravel Cobalt Degradation Mechanisms in Acidic Media for Oxygen and Hydrogen Electrocatalysis
Authors: Aleman Ashton M. , Crago Colin Flynn , Kamat Gaurav A. , Mule Aniket Sandip S. , Nielander Adam C , Burke Stevens Michaela , Jaramillo Thomas F.
Published: December 2024

Cobalt plays a significant role within sustainable energy technologies, including but not limited to hydrogen fuel cells for transportation, lithium-ion batteries for electric vehicles and portable devices, and electrolyzers for renewable hydrogen production. For devices that contain a proton exchange membrane (PEM), such as proton exchange membrane fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs), cobalt-based materials are commonly used to perform the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), respectively. However, the PEM in these devices induces an acidic environment (pH = 1) that cobalt is thermodynamically unstable in under ORR and HER relevant potentials. This instability results in cobalt dissolution and as a consequence, substantial decreases in device performance and lifetime. To mitigate such dissolution of cobalt-based materials in acidic environments, a holistic understanding of cobalt’s degradation mechanism is required. To gain such an understanding, we have developed an experimental platform with comparable in-situ and operando techniques, including on-line inductively coupled plasma mass spectrometry (ICP-MS) and electrochemical mass spectrometry (EC-MS), to concurrently monitor relationships between electrochemical output (current/voltage), time, cobalt dissolution, and product formation (i.e, H2 and H2O).

Under HER relevant potentials in acidic media (0.1 M HClO4), it was observed that cobalt is active for HER and undergoes little to no dissolution (< 10 ppb Co2+) while evolving H2, per comparable EC-MS and ICP-MS experiments. These observations suggest that cobalt stability in acidic media strongly coincides with hydrogen evolution. Additionally, these data showcase a surprising window of stability for cobalt that is different than would have been predicted with classical chemical thermodynamics (i.e., Pourbaix diagrams). Along with cobalt being HER active, we have also uncovered its activity for ORR in acidic media (O2 saturated 0.1 M HClO4). Furthermore, the rate of cobalt dissolution was different in O2 versus N2 saturated electrolyte, where it was observed that cobalt dissolution initially occurs faster (~3x more dissolution) in the presence of O2. Altogether, this work showcases how time-resolved techniques such as ICP-MS and EC-MS can be combined to unravel material degradation mechanisms, with cobalt as a case study. This experimental platform has high potential to accelerate current understandings of material degradation, paving the way for new avenues to design and develop more robust and affordable materials and devices.
Operando Spectroelectrochemical and Computational Techniques to Describe the Mars-Van Krevelen Mechanism on Nitride Mxenes
Authors: Johnson Denis , Lai Hao En , Zheng Yu B. , Djire Abdoulaye
Published: December 2024

The electrochemical nitrogen reduction reaction (NRR) provides an opportunity to convert nitrogen (N2) to ammonia (NH3) at ambient conditions. Protons (H+), which stem from water oxidation, are necessary for this process, but result in the hydrogen evolution reaction (HER) reducing overall selectivity. Another cause for low selectivity in the NRR is the high energy required to activate the N≡N bond during typical associative/dissociative mechanisms. An avenue to mitigate these challenges altogether is available on transition metal nitride materials through the Mars-van Krevelen (MvK) mechanism, where sub-lattice nitrogen atoms are protonated to form NH3, which then desorb to form nitrogen vacancies that require less energy to weaken the N≡N. Recently, we have provided preliminary evidence that the Ti2NT
x
MXene operates through this MvK mechanism. To further corroborate this mechanism, a series of electrochemical and operando spectroscopic techniques, including X-ray absorption spectroscopy (XAS) and Fourier-transform infrared (FTIR) spectroscopy, were utilized. We use XAS to track the Ti oxidation state shift as a function of applied potential to understand the role of the Ti in the MvK mechanism and to understand the dynamic change in the Ti-N-Ti bond network. Furthermore, we use FTIR to elucidate in real-time the adsorption of NRR reactive species and intermediates on the MXene surface, especially with regards to the periodicity of the -NH2 and N-N spectroscopic intensities, which allows for the MvK mechanism to be differentiated from the typical associative/dissociative mechanisms. Finally, we use DFT and AIMD to corroborate the experimental work and further enhance our understanding of the mechanisms of NRR. These findings serve as the foundation to produce green NH3 using earth abundant resources.
(Invited) First Principles Treatments of Oxygenate Electrooxidation – Structure Sensitivity and Influence of Solvent on Chemically Diverse Elementary Reaction Steps
Authors: Greeley Jeffrey , Deshpande Siddharth , Dupleiss Brady , Zeng Zhenhua
Published: December 2024

Advances in the theoretical understanding of electrochemical systems have, over the past decade, led to growing use of periodic Density Functional Theory (DFT) studies to treat a surprisingly large ensemble of electrocatalytic reactions, ranging from carbon dioxide electroreduction to oxygen evolution. Many such studies have employed simplified models of the electrochemical environment to determine reactivity trends across a broad space of catalytic materials, while other efforts have focused on developing detailed descriptions of electrochemical phenomena, such as the structure of electrochemical double layers, on model catalyst structures. An emerging challenge is to combine these approaches to ultimately enable theoretical design of electrocatalysts for reactions of significantly expanded chemical and materials complexity.

In this talk, we begin by discussing how we develop and apply DFT-based methods to study the electrooxidation of ethanol and related oxygenated species on Pt surfaces. We show how explicit double layer models and ab initio molecular dynamics provide exciting insights beyond the traditional computational hydrogen electrode treatments, leading to improved descriptions of elementary reaction steps involving adsorption/desorption of reaction intermediates and proton-coupled electron transfer processes. By combining the aggregate results with detailed microkinetic models and explicit descriptions of adsorbate-adsorbate interactions, we further demonstrate how these effects can influence both the predicted overpotentials and the selectivities to acetic acid, acetaldehyde, and carbon dioxide. We conclude with some perspectives on how these insights may be used to enhance the search for improved oxygenate electrooxidation catalysts.
Theoretical Studies of Hydrogen Evolution Involving Imidazolium Proton Donors
Authors: Bagbudar Zeynep , Warburton Robert
Published: December 2024

The hydrogen evolution reaction (HER) is an important electrocatalytic reaction used for the electrochemical production of hydrogen gas. Its reverse reaction, the hydrogen oxidation reaction, is used to produce protons used in electrocatalytic reduction reactions for various electrochemical energy conversion and storage applications. While many fundamental studies have analyzed interfacial reactivity in aqueous HER, analogous mechanistic understanding of HER reactivity in nonaqueous media remains limited.

In this presentation, periodic density functional theory (DFT) calculations are applied to mechanistic studies of HER on Pt(111) using various imidazolium proton donors. These studies incorporate analyses of imidazole adsorption and potential-dependent activation energies. The conjugate bases of imidazole adsorb strongly to the electrode surface. Yet, the adsorption geometries and energetics are sensitive to substituent effects and isomeric configurations at the interface. The potential-dependent binding geometries and adsorption energies of different imidazoles adsorbed to Pt(111) are analyzed in a dielectric continuum implicit solvent. These calculations demonstrate how imidazole derivatization and electrode surface charge impact the adsorption of imidazole conjugate bases during HER. To gain insights into the kinetics of the elementary Volmer and Heyrovsky steps of HER, potential-dependent reaction energies and activation barriers were calculated using the charge extrapolation method. Energetics were calculated for different electrode potentials by modifying the coverage of protons. This approach was used to develop relationships between reaction thermodynamics and kinetics via Brønsted–Evans–Polanyi relationships for various imidazoles, where this relationship gives charge transfer coefficients in the Butler–Volmer equation. The goal of assessing these reaction parameters is to enhance understanding of charge transfer processes and molecular interactions at the electrode-electrolyte interface, which is essential for the design of high-efficiency energy conversion and storage devices. The potential-dependent adsorption behavior and kinetics of elementary proton-coupled electron transfer steps are used to understand the reaction kinetics of hydrogen evolution in a nonaqueous imidazole-based electrolyte through comparisons to voltammetry measurements. Through these analyses, we identify kinetic trends across functionalized imidazoles, providing valuable perspectives for the development of catalytic systems and energy storage technologies.
(Invited) Impact of Site Heterogeneity of Cu on the Electrochemical CO2 Reduction Reaction
Authors: Xu Yifei , Gao Wenqiang , Chang Xiaoxia , Xu Bingjun
Published: December 2024

Electrochemical CO2 reduction reaction (CO2RR) has been widely acknowledged as a key component in the global transition from fossil energy to renewable energy powered society to combat climate change. Cu is the only metal capable of converting CO2 to valuable multicarbon products with decent yields. Despite intense research efforts, mechanistic understanding of Cu-catalyzed CO2RR remains incomplete. A key point with impactions for catalyst design is whether the CO2-to-CO conversion and the further conversion of CO are independent steps in the reaction network of the CO2RR. In this talk, I will discuss our recent results showing that the presence of CO2 enhances the Cu-catalyzed CORR to multicarbon products, and intriguingly, not by acting as an additional surface of carbon. Co-electrolysis studies show that there are at least two types of Cu sites with distinct activities, with one type favoring the CO2-to-CO conversion (CuCO2), and the other more active in the CORR (CuCO). Analysis based a proposed two-site model shows that CO adsorbed on CuCO is at least six times more active in the formation of multicarbon products than that on CuCO2. Experiments conducted on single crystal Cu facets suggest that CuCO2 corresponds to Cu(111)-like sites and CuCO is associated with undercoordinated Cu sites.
(Invited) In Situ Spectroscopic Studies on CO2 Reduction
Authors: Shao Minhua
Published: December 2024

The reaction pathways of CO2 electrochemical reduction reaction have been barely understood due to lack of direct molecular level information. In this study, we use the surface-enhanced infrared absorption spectroscopy with the attenuated total reflection configuration to directly monitor the reaction intermediates of CO2 reductions on both model and nanocatalysts. Reaction mechanisms according to the spectroscopic and theoretical calculation results will be proposed. Rational design of electrocatalysts for these reactions will be presented.
(Invited) Operando Spectroscopy-Inspired Design of Electrolyte-Electrode Interface
Authors: Katayama Yu
Published: December 2024

There has been a growing recognition that not only electrocatalysts but electrolytes influence the activity of surface electrocatalytic reactions. Therefore, understanding the electrolyte-electrode interface under realistic operating conditions is critical to designing active and stable electrochemical devices. The past few decades of research have focused on developing a range of spectroscopic and imagining tools to enable the study of the chemical and structural changes at the electrolyte-electrode interface. Here, we introduce operando surface-enhanced infrared absorption spectroscopy (SEIRAS), a promising lab-based tool for gaining a molecular-level understanding of interfacial electrochemical processes.

This talk will bring the most recent understanding of the electrochemical interface during the operation of electrolysis applications, including electrochemical CO2 reduction reaction and water splitting, using operando SEIRAS. Furthermore, we demonstrate that the holistic information about the complex interaction in the electrochemical interface can alter the reaction energetics/kinetics in a way incapable of electrode-centered design strategy. We will highlight the significance of advanced operando techniques to accelerate the design of electrochemical interfaces by providing additional knobs to tune the reaction energetics/kinetics, leading further improvements in electrocatalytic activity for energy conversion and storage reactions.
Deconvoluting Alkali Metal Cation and Hydroxide Anion Effects on the Alkaline Hydrogen Evolution and Oxidation Reactions on Platinum
Authors: Wang Sibo , Wan Chengzhang , Shah Aamir , Huang Yu , Duan Xiangfeng
Published: December 2024

The platinum (Pt) catalyzed hydrogen evolution and oxidation reactions (HER/HOR) usually show considerable slower kinetics in alkaline electrolytes than that in acidic environment. The fundamental origin of such distinct kinetics has been a topic of considerable interest. In general, the electrode-electrolyte (Pt-water) interface in alkaline electrolytes is far more complex than the acidic environment due to the presence of alkali metal cations (AM+) and hydroxide anions (OH-) as potential competitive surface adsorbates and interfacial species that may fundamentally change the local chemical environment. Despite considerable efforts in probing the HER kinetics in alkaline electrolytes, the effects of different species are often highly convoluted, and the exact role of each specie is difficult to resolve.Herein, we conduct a systematic study to deconvolute the effects of AM+ and OH- by designing twenty-eight electrolytes from 0.001M NaOH to 1M NaOH. Our study reveals a nontrivial dependence of HER/HOR activities on the AM+ or OH- concentrations. The electrochemical measurements and electrochemical impedance spectroscopy (EIS) analyses demonstrate an apparent correlation between the kinetic exchange current density, charge transfer resistance and the electrical double layer capacitance. It is found that the increasing OH

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concentration reduces the electrical double layer thickness, increases the surface electric field
and the OHad coverage
to lower the kinetic barrier for water dissociation (for HER) or Had and
OH

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recombination (for HOR). The Na+ shows a positive effect at low concentration by decreasing the double layer thickness and increasing surface electric field to polarize the interfacial water; but a negative effect at high concentration by forming ion pairs that reduces interfacial water polarization and rigidify the interfacial water layer to slow the transport of the reactants and products to and away from the electrode surface. These combined effects result in a complex cation and pH dependent HER/HOR activities. This study for the first time deconvolute the effect of AM+ and OH- concentrations and establishes a comprehensive view of their roles in the Pt-catalyzed alkaline HER/HOR, offering valuable insights for further electrocatalyst design.