bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrodeposited Pt-Rh Thin Films for Enhanced Ammonia Oxidation Rates Via Electronic Modifications
Authors: Paliwal Akhil , Long Haowei , Assaf Lina , Kenis Paul J.A , Gewirth Andrew A.
Published: December 2024

Ammonia has garnered significant attention as a promising hydrogen carrier due to its high volumetric energy density, and its compatibility with existing fuel cell technologies. Electrochemical ammonia oxidation reaction (AOR) can facilitate the release of hydrogen from ammonia at the point of use, enabling on-demand hydrogen production without the need for high pressure storage. However, current AOR catalysts struggle with high overpotentials, sluggish kinetics and susceptibility to poisoning by AOR by-products. We report the AOR activity of electrodeposited bimetallic PtRh alloy nanoparticle catalysts. The dilute Pt92Rh8 catalyst showed less overpotential and higher activity than Pt and more concentrated PtRh samples. Valence-band X-ray photoelectron spectroscopy (XPS) showed that Rh shifts the d-band center of Pt towards the Fermi-level which tunes the adsorption energy of AOR intermediates. Furthermore, pre- and post-AOR nitrogen and oxygen XPS of the samples provided insight into the nature of poisoning species on the Pt and alloyed surfaces. The Pt-only surface was found to be more oxidized than the Pt92Rh8 surface post-AOR which indicates higher N2 selectivity and less NOx formation on the Pt92Rh8 surface. Analysis of product gas stream through gas chromatography will be reported. This study offers a design platform for the development of future Pt-based AOR electro-catalysts.
(Invited) Organic Photoelectrochemical Cells for Overall Solar Water Splitting
Authors: Cho Han-Hee
Published: December 2024

Solar-driven water splitting to produce hydrogen and oxygen offers a promising avenue for reducing reliance on fossil fuels as hydrogen can be converted into electrical energy using a fuel cell or transformed into useful chemical feedstocks. Despite its potential, the search for cost-effective light harvesting semiconductors suitable for industrial-scale deployment remains a challenge. Organic photoelectrochemical cells (OPECs) utilizing organic semiconductors (OSs) coupled with co-catalysts have recently attracted great attention as alternative photoelectrodes for solar water splitting, considering the unique features of OSs such as precisely tunable optoelectrical properties and solution-processability at low temperatures. However, the conversion efficiency and stability of OPECs (both photocathode and photoanode) have remained particularly poor. Herein, I present high-performance and robust organic photoelectrochemical cells by employing a bulk heterojunction (BHJ) blend of semiconducting polymers as a photoactive layer. The in-depth study using sacrificial agents for photoreduction and photooxidation unveils critical parameters that significantly affect the performance and operational stability of OPECs: (i) rational selection of semiconducting polymer donor and acceptor to generate free charges efficiently and ensure chemical stability upon illumination, (ii) large surface roughness of interlayers to improve interfacial adhesion, and (iii) mitigation of charge accumulation at the interfaces. By leveraging these findings, the optimized polymer BHJ photocathode and photoanode show outstanding performance and robustness compared to previous OPECs, demonstrating a new benchmark of OPECs in solar water splitting. Consequently, this advancement, combined with the simplicity of the polymer blending process, establishes the use of polymer BHJs as a promising route for efficient and scalable solar-driven water splitting technology.
(Invited) Photoreactors for Benchmarking Outdoor Solar Hydrogen Production: Future Designs Based on Lessons from the Past
Authors: Deutsch Todd G , Oh Kiseok , Lenef Julia , Young James L.
Published: December 2024

Outdoor testing under realistic environmental conditions, including natural (diurnal) solar illumination, is a necessary step in moving photoelectrochemical water-splitting technologies from the laboratory towards a deployed technology. This is because many have found that a good laboratory result does not translate to success in the field. This is both due to the scale of devices tested as well as simulated conditions not adequately representing the stresses materials will experience under “real” operating conditions. In the first part of this talk, we will describe lessons learned from previous experience in designing photoreactors and results from their outdoor testing in Golden, Colorado. Bubble management, temperature control, and auxiliary component durability are some of the issues we had to address.

In the second part of this talk, we will discuss how we have applied the knowledge gained our prior experience to design more advanced photoreactors. We will also describe a new testing platform we are designing and building that will be used to benchmark the performance of photoreactors based on several different photoabsorbers developed by partners in the HydroGEN advanced water-splitting technologies consortium.
(Invited) Experimental Insights into the Local Chemical Environment of Sulfur Atoms and Their Relevance in Photoelectrochemical Water Splitting Devices Made of Cu(In,Ga)(S,Se)2 and Other Things
Authors: Heske Clemens
Published: December 2024

It is the purpose of this presentation to demonstrate how the unique capabilities of novel x-ray spectroscopy methods (in particular element-specific soft x-ray emission spectroscopy, XES) can be employed to derive important insights into PEC and other solar devices from the viewpoint of sulfur. Of course, other elements will also play a role, as will delocalized valence and conduction bands, but sulfur is unique and deserves to be celebrated.

The presentation will include results from lab-based x-ray and UV photoelectron spectroscopy, inverse photoelectron spectroscopy, and x-ray-excited Auger electron spectroscopy, complemented by XES and soft x-ray absorption spectroscopy using high-brilliance synchrotron radiation. A particularly powerful approach is their resonant combination, Resonant Inelastic soft X-ray Scattering (RIXS), best displayed in a “RIXS map”.

In the presentation, we will discuss the impact of sulfur on the electronic level alignment at surfaces and interfaces, and how to go about learning more about local chemical bonding (hybridization) in the vicinity of sulfur atoms, using a large variety of compounds as examples – sulfides, sulfates, chalcopyrites, ... The presentation will thus also include a bit of a discussion of cutting-edge instrumentation recently developed for studying buried layers and materials in in situ and operando environments, such as the novel X-SPEC beamline and its unique endstations at the KIT Light Source in Karlsruhe, Germany.
(Invited) Vapor-Fed Photoelectrochemical Water Splitting Using Porous Photoanodes Functionalized with Surface Electrolytes
Authors: Amano Fumiaki
Published: December 2024

Photoelectrochemistry is used to develop solar energy technologies for fuel production and chemical transformations. Semiconductor materials such as TiO2, WO3, BiVO4, Fe2O3, and Cu2O are often investigated in devices designed to convert light energy into chemical energy, including for the production of hydrogen by photoelectrochemical (PEC) water splitting. The oxide electrodes are of significant interest due to their potential for efficient PEC reactions with high durability and their relatively low costs compared to other semiconductor materials. This presentation provides an overview of recent advancements in gas-fed PEC systems specifically designed for utilizing water vapor as a hydrogen resource. The gas-fed PEC system utilizes a proton exchange membrane (PEM) as a solid polymer electrolyte. Additionally, it utilizes gas-diffusion photoelectrodes composed of a fibrous conductive substrate with macroporous structures and semiconductor oxide particles. Herein, the porous photoelectrodes are composed of n-type oxides for oxygen evolution reactions and used with a Pt electrocatalyst cathode for hydrogen evolution reactions. The topics covered include the conceptual framework of vapor-fed PEC hydrogen production, the strategic design of gas-phase PEC reaction interfaces, and the development of porous photoanodes for an oxygen evolution reaction. A significant enhancement in the PEC efficiency was achieved through the application of a thin proton-conducting ionomer film on these porous photoelectrodes for surface functionalization. The rational design of proton exchange membrane-based PEC cells will play a pivotal role in realizing renewable-energy-driven hydrogen production from atmospheric humidity in the air.

Figure 1
Probing Photocatalytic Oxygen and Hydrogen Evolution Reactions via Single Particle Electrochemistry with Photo-SECM
Authors: Askarova Gaukhar , Wu Shu , Mirkin Michael V.
Published: December 2024

Particulate photoelectrocatalysts (PEC) have attracted substantial attention due to their potential for renewable fuel generation from sunlight and water. The characterization of reactivity at the active sites of photocatalysts with nanometer-scale spatial resolution is essential for understanding and developing more efficient energy conversion systems. In this study, we present the results of the first single-particle-on-microelectrode oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity measurements assisted by in situ photoelectrochemical scanning electrochemical microscopy (photo-SECM). An individual micrometer-sized Al-doped SrTiO3/Rh2–yCryO3 photocatalyst crystal was immobilized on a carbon fiber microelectrode and probed using a Pt nanoelectrode at various substrate bias conditions to promote OER and HER. Local fluxes of oxygen and hydrogen generated by an individual PEC microcrystal were quantitatively evaluated with COMSOL Multiphysics finite-element simulations.
Optical and Electrochemical Effects of Semiconductor Nanoparticle Clustering on Photocatalytic Water Splitting Half-Reactions
Authors: Lentz Rebecca , Bala Chandran Rohini
Published: December 2024

To meet increasing demands for carbon-reduction, renewable and low-emission fuel alternatives have been proposed as a replacement for carbon-intense natural gas and coal. Specifically, hydrogen and oxygen evolution have been demonstrated at the lab-scale through a room temperature water-splitting process using only water, sunlight, and suspended semiconductor nanoparticles as inputs. Recent advancements in improving the efficiency of this water-splitting process focus on methods to boost charge separation, chemical selectivity, and optical band-engineering. However, there is a growing need for demonstrations at scale that also consider nano-particle interactions as an ensemble. Additionally, Z-scheme reactor designs have motivated the study of oxidation and reduction half-reactions using charge-carrying ions as an intermediary. This work studies how photocatalytic rates of half-reactions driven by semiconductor nano-particle suspension are affected by the inevitable presence of aggregation and agglomeration. The effects of solution pH, Fe(III) concentration, input light intensity, reaction temperature, stirring and sonication, nanoparticle concentration and size, and material quality are experimentally characterized by the desired ion evolution reaction rates and external quantum yield. Additionally, the effects of these variables on the zeta potential, optical scattering, particle aggregation, and mass transport are also experimentally measured to probe ensemble behavior and nano-particle interactions. Results indicate the importance of balancing ion concentration and pH to reduce aggregation via enhanced zeta potential nanoparticle repulsion, while also avoiding competitive absorption from suspended intermediary ions and their respective pH-dependent hydrolysis states. Reaction modeling further motivates investigation into charge-transfer limitations and enhancements due to aggregation states that cannot be explained by optical effects alone.
Deposition and Characterization of Photocatalytically Active Nanowires Viascanning Electrochemical Probe Microscopy
Authors: Caniglia Giada , Oswald Eva , Hellmann Andreas , Gaus Anna-Laurine , von Delius Max , Kranz Christine
Published: December 2024

Producing clean energy is one of the world's greatest challenges today. The use of solar energy to split water into hydrogen and oxygen is therefore of great interest. In addition to semiconductor materials, heterogenized molecular catalysts for the hydrogen evolution reaction (HER) and water oxidation catalysts (WOC) have attracted considerable interest. The development and design of artificial molecular devices (i.e. artificial photosynthesis systems) using visible light requires the heterogenization of catalysts (CAT) and photosensitizers (PS). However, the correlation of structural heterogeneity, leaching of active components and degradation processes during illumination, as well as the continuous monitoring of reactivity have not been fully addressed.1,2 Scanning electrochemical probe microscopy such as atomic force microscopy (AFM), scanning electrochemical microscopy (SECM), scanning electrochemical cell microscopy (SECCM), and scanning photoelectrochemical microscopy (SPEM), have been used to map light-driven water splitting and local electron transfer kinetics under in situ and operando conditions.3-5

In this contribution, we present the deposition of mixed CAT/PS nanowires using earth-abundant BPh2-bridged, organometallic cobaloxime CATs and Ru-based ([Ru(tbbpy)2(mmip)]Cl3) PS on various substrates using SECCM. Based on different studies an cabolime microarrays6, the nanowires are characterized with respect to their stabilty, elemental composition as well as their light-driven H2 evolution activity. The H2 evolution of nanowire arrays is imaged via SECM using Pd- and Pt-Black modified microelectrodes. In addition, submicron-sized electrocatalytically active cantilever-based probes, recently developed by our group, are used for improved lateral resolution. These probes can be used for colloidal force spectroscopy7,8 providing nanomechanical properties of the studied materials. A thorough characterisation of the cantilever-based sensors will be presented together with nanomechanical and activity mapping of nanowires with different CAT/PS ratios.

References:

1 C. Kranz, M. Wächtler, Chem. Soc.
Rev.
50, 1407
,
2021
.

2 C. Santana Santos et al., Chem.
Rev.
123, 4972, 2023.

3 J. Kund et al., Angew. Chem. Int. Ed.
22, e202217196, 2023.

4 G. Askarova et al., Anal. Chem.
94, 7169, 2022.

5 J.T. Mefford, et al., Nature, 593, 67, 2021.

6 E. Oswald et al, Chem. Eur. J.
27, 16896
,
2021.

7 H.-J. Butt, Biophys. J.
60, 1438, 1991.

8 S. Daboss, Anal.
Chem.
92, 8404, 2020.

This work is part of the TRR 234 “CataLight” project that has received funding from the Deutsche Forschungsgemeinschaft (German Science Foundation), DFG. Project number 36454990.
Unveiling Complex Interfaces: A Methodological Approach for Accurate Apxps Data Acquisition of Polymer Electrolyte Membrane Electrolysis Devices
Authors: Hamlyn Rebecca , Mahl Johannes , Crumlin Ethan J.
Published: December 2024

Electrochemical water splitting is a promising pathway for the production of green hydrogen as an alternative fuel, chemical feedstock and storage medium for renewables. Yet, the process is hindered by slow kinetics of the oxygen evolution reaction at the anode. Also, large scale implementation will require reduced loadings of expensive and rare platinum group metals and development of new materials. Making progress on rational design for OER catalysts requires effective characterization of the electrode-electrolyte interface where the chemistry takes place. Synchrotron-based x-ray photoelectron spectroscopy (XPS) offers a versatile way to obtain surface chemical and elemental characterization of such materials. The use of X-rays in the tender regime (~2-6 keV) allows for deeper probing than the conventional soft X-ray (< 2 keV) energies that are common for this technique. The photoelectrons generated from tender x-rays have enough energy to penetrate tens of nanometers through low-density components such as a layer of liquid or polymeric electrolyte, allowing access to interfaces in operando conditions. At Beamline 9.3.1 of the Advanced Light Source, we have developed a fully operational two-electrode system to study these membrane electrode assemblies under active water-splitting conditions.

Accurate and representative data collection can involve a series of considerations and tests during acquisition. In this talk, I will explain our specific approach, which combines conventional and sub-second snapshot acquisition modes to minimize beam effects and test for phenomena that can contribute to erroneous interpretation of data. I will demonstrate the efficacy of this approach with results on a series of iridium-based polymer electrolyte membranes. With the application of elevated potential, we can correlate the iridium valency and surface species with the appearance of product traces in a mass spectrum.
Shedding Light on Active Site Reconstruction and Structural Transformation of Oxygen Evolution Reaction Catalysts for Water Electrolysis
Authors: Ham Kahyun , Lim Ahyoun , Spanos Ioannis
Published: December 2024

Designing efficient and stable electrolcatalysts for the demanding oxygen evolution reaction (OER) in water electrolysis is challenging and we are still lacking fundamental understanding of the underlying processes related to catalyst transformations governing their final activity and stability. Only the combination of operando spectroscopy techniques with electrochemical measurements can promote a deeper understanding on the interplay of different phenomena taking place during OER [1].

In this work, we utilize operando techniques like X-ray Absorption Spectroscopy (XAS) and Surface Enhanced Raman Spectroscopy (SERS) [2], in combination with specifically designed electrochemical protocols to study i) the reconstruction/reactivation of active sites in Ir-based OER catalysts for acidic media (Fig. 1a-c) and Ni-based OER catalysts for alkaline media (Fig. 1d) and ii) the identification of the relevant OER active species which will eventually define the final electrocatalyst performance [3]. We show not only the formation of the active species for OER but also the dynamic operando transformation of the Ir- and Ni-based electrocatalysts before the onset of OER but also their structural transformation due to electro-oxidation during OER, processes that lead to the final active phase.

The underlying mechanisms studied via our operando analysis provide fundamental understanding of reaction mechanism but also guidance for the design of efficient OER catalysts optimized for their operation in technical devices.

References

[1] Spanos I, Tesch MF, Yu M, Tüysüz H, Zhang J, Feng X, Müllen K, Schlögl R, Mechler AK: ACS Catal 2019, 9:8165-8170.

[2] Lim A, Ham K, Tesch MF, Spanos I: to be submitted

[3] Lim A, Ham K, Tesch MF, Spanos I:Current Opinion in Electrochemistry 2023, 39:101272

Figure 1
Contrasting Theories of Electrode Models in Electrocatalysis Under Aqueous Alkaline Solutions
Authors: Tang Michael T. , Bajdich Michal , Ablid-Pedersen Frank
Published: December 2024

The computational hydrogen electrode (CHE) model has been a mainstay tool for understanding electrochemical reactions over electrocatalytic surfaces. While the electrode model has seen success in modeling catalysis under highly acidic solutions, over recent years, focus has shifted towards electrochemistry under neutral or alkaline solutions. In such cases, various correction schemes have been applied onto the computational hydrogen electrode in order to address its inability to describe pH dependent effects. Many of these schemes are often computationally cumbersome and not very transferrable across various material systems/ cell systems. In this presentation, we will breakdown the working assumptions of the computational hydrogen electrode and more recent grand canonical based models and present a new simple electrode model using density functional theory (DFT) and thermochemical data to describe reduction pathways as well as mechanisms that lead to corrosion on the electrode surface. Consistent with the original CHE model, the new electrode model is capable of referencing any charged surface intermediates to their aqueous ionic counterpart in solution in the standard concentration, such that they can be used to address problems of the original CHE model. The thermodynamic implications of our model can be incorporated into experiments and cell designs to understand the effects of ions in aqueous electrocatalytic reactions.

Figure 1
Interplay of Surface Hydride, Hydrogen Evolution, and Oxygen Reduction on Cu(111)
Authors: Raciti David , Guo Ally , Moffat Thomas P
Published: December 2024

Copper is presently the material of choice for hydrogenation reactions converting CO2 or CO to hydrocarbons and oxygenates although the identity and role of adsorbed reaction intermediates remains unresolved and understudied. Accordingly, the interactions between C, O, H, and molecules comprised thereof, with different Cu surfaces, defects and applied potentials are of substantial interest. This talk will focus on the dynamic interplay between surface hydride formation, hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) on Cu(111) in perchloric acid electrolyte using electrochemical mass spectrometry (EC-MS). Voltammetric EC-MS unveils a two-stage process for surface hydride formation, with recombination to H2 occurring at specific potentials. Controlled introduction of O2 into the cell does not disrupt hydride coverage, while its recombination potential correlates with the transition from mass-transport-limited ORR kinetics to mixed control ORR kinetics. Concurrent ORR accelerates steady-state HER onset, with a sharp increase in transient H2 production upon potential stepping. Furthermore, convolved voltammetric waves suggest surface restructuring due to O2 exposure post-ORR. These findings elucidate the complex interactions between surface species and electrochemical behavior, shedding light on Cu's catalytic selectivity and the impact of O2 on its electrochemical properties.
Electrolyte Effects on Reactive Carbon Capture in Ionic Liquids
Authors: Nkurunziza Francois , Gautam Manu , Muchharla Baleeswaraiah , Kumar Bijandra , Spurgeon Joshua M.
Published: December 2024

Reactive carbon capture (RCC), or integrated CO2 capture and electrochemical conversion, is a promising strategy to improve the energy efficiency and technoeconomics of the electrochemical reduction of CO2 from dilute sources. Ionic liquids are a class of functional solvents for RCC that can have high CO2 solubility and complex with CO2 to make an adduct species that lowers the activation energy and associated onset potential for CO2 reduction. Work is ongoing at the Center for Closing the Carbon Cycle, a DOE Energy Frontier Research Center, to understand which aspects of direct aqueous electrochemical CO2 reduction are translatable knowledge for RCC using ionic liquids. RCC behavior in imidazolium ionic liquids has been studied on exemplar catalysts including Ag and Sn as a function of variable electrolyte properties including ionic liquid concentration, solvent, supporting electrolyte cation, and pH. In particular, the effect of alkali cations was notably different from the behavior reported for aqueous-only CO2 reduction, with alkali species inhibiting CO2 reduction product selectivity in the presence of ionic liquid. In addition, the reduction of imidazolium carboxylate compounds has been investigated for further insight into the reduction of ionic liquid imidazolium cation-CO2 adducts.
Establishing a Platform for Probing Reactive Carbon Capture in Ionic Liquids through Non-Aqueous Electrochemistry
Authors: Brower Rowan Shae , Velazquez Jesus , McCrory Charles , Gurkan Burcu E
Published: December 2024

The successful reactive carbon capture (RCC) and subsequent storage of atmospheric CO2 plays a pivotal role in advancing renewable energy and mitigating greenhouse gas emissions. Despite significant progress in reactor, catalyst, and microenvironment design in aqueous media, achieving optimal CO2 conversion efficiency, reproducibility, and selectivity in non-aqueous media remains a challenge. Promising strategies for developing pragmatic systems in anhydrous environments include controlling efficiency, selectivity, and reproducibility by enhancing local microenvironments of metallic surfaces with polymer overlayers and utilizing metallic surfaces to benchmark the RCC capability of ionic liquids. This research indicates that employing surfaces with bulk or trace metallic Pb is an ideal platform for exploring these strategies. Results show that in non-aqueous electrolytes we have successfully created an enhanced microenvironment on trace metallic Pb for selective CO2 conversion to oxalate on carbon supports. Notably, trace metallic Pb on the ppb scale demonstrates comparable faradaic efficiencies (FE), FEZnC2O4 ~ 84%, to bulk metallic Pb, FEZnC2O4 90%, from -2.1 to -1.8 V vs. Fc/Fc+ for the reductive coupling of CO2, and polymer encapsulation of trace Pb fosters an enhanced microenvironment promoting oxalate selectivity over CO. Furthermore, when polarized Pb electrodes are used in non-aqueous electrolytes containing ionic liquids there is a substantial shift in product selectivity from oxalate to more efficient CO production, allowing for the RCC capability of ionic liquids to be compared. The RCC capability of the ionic liquids can be compared as the shift in selectivity from oxalate to CO indicates a mechanistic change that only occurs in the presence of ionic liquids. The ionic liquids tested in this work include [EMIM][OTF], [EMIM][BF4], [EMIM]-[TFSI], and [EMIM][2-CNpyr]. Notably, [EMIM][2-CNpyr] had the most promising RCC capabilities as it exhibited no oxalate product and almost exclusively CO production (FECO~70%).
CO2 Electrolysis Coupled with Hydrogen Oxidation Reaction in Non-Aqueous Aprotic Electrolytes
Authors: Longhin Francesco , Mygind Jon Bjarke Valbaek , Bylov Nielsen Frederik , Seger Brian
Published: December 2024

CO2 electrolysis (CO2E) coupled with renewable energy is an important strategy to mitigate the effects of the green house gas in the atmosphere. By effectively transforming CO2 into higher value chemicals and fuels, the carbon cycle can be closed.[1] In order to produce C2+ products, most of the studies have been done in aqueous electrolytes, using Cu based catalysts. Nevertheless, these systems show different critical problems. First, in low temperature CO2E, CO2 carbonation in water is the primary source of energy and carbon losses.[2] Moreover, these systems rely on low faradaic efficiencies (FE) towards the single C2+ products (ethylene, ethanol, propanol). CO2E in organic aprotic electrolyte is gaining more and more attention due to the possibility of controlling the proton dynamics and the higher FE towards target products, mainly CO and oxalate. One challenge of these systems is the counter reaction. Many are using sacrificial anodes, which are not suitable for continuous industrial application.[3] Hydrogen oxidation reaction (HOR) is a promising reaction that could lower down the overall cell voltage, and, at the same time, produce more protonated products. This approach is not new in these systems, lithium mediated ammonia electrosynthesis, for example, has achieved relevant results using HOR at the anode and aprotic based electrolytes.[4]

Based on these prerogatives, this study investigates the feasibility of couple CO2E with HOR in organic aprotic systems with controlled water content. A DMF/TBAPF6 electrolyte was used due to the good CO2 solubility (194 mmol L-1)[5] and conductivity. The rotating disk electrode experiments set up in a glovebox proved the stability of the chosen electrolyte, with a potential window of 3.6V, a HOR’s onset potential at -0.5V vs Ag/AgCl, and an onset potential for CO2 reduction at around -1.5V vs Ag/AgCl. A gas diffusion electrode (GDE) cell was used to perform CA or CP studies. A sputtered Cu GDE was used at the cathode. At the anode, an electrochemical deposited Pt/Au GDE was implemented for the HOR. [4] From the gas analysis, CO, H2 and ethylene have been detected at current densities of 10 mA/cm2. To investigate further the catalyst stability, XPS and SEM were used on the catalyst before and after the electrochemical reaction. ICP-MS analyses were done on the electrolyte to assess the eventual metal leaching during reaction.
Catalysts Tolerant to SO2 for Electrified Carbon Capture and Utilization
Authors: Ou Pengfei
Published: December 2024

CO2 electrolysis studies typically employ pure CO2; yet the most plentiful point sources of CO2 also contain sulfur dioxide (SO2) at the level of hundreds or even thousands of parts per million (ppm), and purifying CO2 from these sources is costly. Here we find that when including SO2 in the CO2 stream (50% CO2, 50% N2, and 400 ppm SO2), the Cu catalyst loses selectivity to multicarbon (C2+) products within 2 hours, its productivity shifting to formate and hydrogen. We use computational screening to realize a heteroatom-doping strategy to enable SO2-tolerant CO2 electrolysis to C2+ products from a SO2-containing CO2 stream. We find that, among 18 dopants screened, Ru provides the greatest benefit in increasing resistance to surface sulfidation; it simultaneously stabilizes *COOH over *HCOO, enhances CO coverage and facilitates C-C coupling, and is thus projected to retain selectivity to C2+ products even when *S resides on the Cu surface. We find experimentally that the C2+ Faradaic efficiency (FE) of undoped Cu decayed to 8% following 6 hours of operation at 200 mA cm−2; while Ru/Cu maintains FE > 50% following 40 hours at the same current density.
Plasmon-Driven Selective Methane Conversion to Higher-Value Products
Authors: Lee Sanghyuk , Ryu Jaemin , Park Juneseo , An Yeongju , Yu Sungju
Published: December 2024

The conversion of methane into energy-dense products presents an opportunity to optimize the utilization of fossil fuels while reducing greenhouse gas emissions. However, this process is hindered by the high activation energy required for C-H bond cleavage. In this study, we explored the use of plasmonic catalysis to facilitate C-C coupling of methane. The excitation of gold nanoparticles with visible light created a locally enhanced electromagnetic field that induced dipoles in the nonpolar C-H bonds. This reduced the activation energy for C-H bond dissociation, enabling the conversion of methane into C2+ hydrocarbons under mild conditions without the need for strong sacrificial oxidants. Furthermore, we demonstrated the potential to modulate the selectivity of this plasmonic catalytic process by tuning the plasmon energy. Our findings show the promise of plasmonic catalysis for efficient and selective conversion of methane into valuable products.
Hot Carrier Generation and Extraction from Slow Photons
Authors: An Yeongju , Lee Sanghyuk , Park Juneseo , Ryu Jaemin , Yu Sungju
Published: December 2024

Plasmonic nanostructures, characterized by localized surface plasmon resonance (LSPR), facilitate strong interactions with light and induce collective oscillations of conduction band electrons on metal nanoparticle surfaces. This process enhances light absorption and promotes the generation of hot carriers. However, their energy conversion efficiency is often limited by challenges such as rapid charge recombination and restricted light absorption. We integrated Ag nanoparticles (NPs) with periodically ordered SrTiO3/TiO2 nanoarrays (NAs). These NAs create photonic stopbands, that were precisely aligned to coincide with the LSPR band of the Ag NPs. This configuration confines light effectively within the structure, thereby enhancing the LSPR-induced electron generation. The stepwise structure of SrTiO3/TiO2 further facilitated the efficient collection of these energetic electrons. This synergistic combination of plasmonic and photonic elements resulted in a substantial improvement in non-equilibrium electron harvesting efficiency. Under LSPR excitation at 500 nm, a rate of 3.1 × 10⁻⁴ electrons per absorbed photon was achieved. The findings demonstrate a strategy for harnessing plasmon energy, with potential applications in fields such as photocatalysis and photovoltaics.
Chemical Sensing Using Thermocouple Cantilevers: Pushing Toward Quantum Sensing
Authors: Zhao Yaoli , Chakraborty Patatri , Passian Ali , Thundat Thomas
Published: December 2024

Detecting and quantifying minuscule quantities of chemicals with high molecular selectivity remains a measurement challenge. We present a photothermal spectroscopic method that exploits the Seebeck effect in a finely engineered nanoscale thermocouple junction at the apex of a microcantilever. The temperature variations driving this thermoelectric effect are induced by the nonradiative decay of molecular adsorbates, efficiently excited by a tunable infrared source. This approach not only benefits from an extremely small thermal mass and superior thermal insulation but also achieves an atto-gram detection limit. The simplicity and compactness of its electronic readout further enhance the method's applicability. In this work, we demonstrate the detection of photothermal spectra for physisorbed trinitrotoluene (TNT) and dimethyl methylphosphonate (DMMP) molecules, as well as representative polymers, with estimated masses as small as 10-18 grams. Our findings underscore the potential of classical measurement techniques to approach the sensitivity and selectivity limits required for molecular detection. Establishing such classical limits is an important part of transitioning into the quantum-sensing regime, which aims to explore new enhancements in sensitivity and selectivity in chemical sensing beyond the conventional limits.
Electrodeposited Magnetoelastic Sensors for Ground Fault Current Detection
Authors: Pillars Jamin R. , Subramania Ganesh , Monson Todd , Finnegan Patrick Sean
Published: December 2024

Magnetostrictive NiFeCo alloy films were investigated for use as sensors for ground fault current detection in photovoltaic systems. The magnetic field generated by a ground fault current applies a bias magnetic field to the magnetoelastic sensor, shifting the resonant frequency, and allowing for the detection of current in the microamp range. These are low-cost, passive sensors, that can be implemented to provide real time monitoring of PV systems and the early detection of failures in a system. Electrodepositing these films enables batch fabrication of thick (10-100µm) resonators with controlled resonant frequencies and optimization of material properties (magnetic, mechanical, and electrical) for increased sensitivity and signal amplitude.

Dopants such as boron and holmium were used to increase electrical resistivity and magnetic permeability respectively. Controlling intrinsic stress was managed through additive selection and allowed for the release of planar resonators with a multistep microfabrication process. The composition and properties of the deposited films were controlled by temperature, agitation, concentrations in the electrodeposition chemistry, current density, and a post processing anneal step. The samples were analyzed with EDS to determine the composition and XRD to look at film texture. Magnetic testing was performed using a super conducting quantum interference device (SQUID) magnetometry and vibrating sample magnetometry (VSM). Magnetostriction was measured using an optical method and correlated to material properties.

Acknowledgement

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Optimizing Sensitivity of Room Temperature CO2 Sensors through Co-Doped ZnO Nanorods By Magnetron Sputtering System
Authors: Soltabayev Baktiyar , Tangirbergen Abylay , Raiymbekov Yessimzhan , Nuftolla Aidarbek , Turlybekuly Amanzhol , Yergaliuly Gani , Mentbayeva Almagul
Published: December 2024

Metal oxide semiconductors (MOS) based gas sensors have been identified as a promising solution for future applications due to their exceptional electrochemical, physical, and gas sensing properties. Due to their excellent optical and electrical features, ZnO nanostructures have become increasingly popular for gas detection applications, mainly because of their abundant availability. Despite its potential, the ZnO-based sensors have challenges such as poor selectivity and high power consumption at elevated operating temperatures. Transition metal doping, for example with cobalt depicted decent promising results in high response and selectivity of ZnO nanomaterials towards certain gasses. This study investigates the sensitivity enhancement of room temperature CO2 sensors utilizing the cobalt-doped ZnO (CZO) nanorod architecture. The CZO thin films were deposited on glass substrates using radio frequency (RF) magnetron sputtering at varying powers. Structural, morphological, and gas response properties of the CZO thin films were analyzed.

Figure 1 illustrates the evolution of resistance over time for CZO sensors when exposed to CO2 gas concentrations ranging from 1 to 500 ppm at room temperature in dry air. In this investigation, the response to gas follows a consistent linear pattern within the 1−300 ppm range. However, as the concentration rises, a noticeable deviation towards nonlinearity becomes more pronounced. The sensor exhibits a heightened response across various concentration levels: 1 (8.9), 50 (12.5), 100 (14.79), 150 (15.7), 250 (18.82), and 500 (23.52) ppm. Discrepancies in the sensor response are attributed to the distinct surface morphology inherent to each sensor type. The introduction of co-doping enhances the occurrence of point defects and oxygen vacancies within the CZO sensors. The Scanning Electron Microscopy (SEM) images reveal that the CZO material exhibits a highly organized surface morphology, characterized by densely packed spherical structures, and the cross-sectional analysis of the material shows a uniform thickness of 136 nm, indicating its potential applications in the field of sensing and detection, shown in figure 2. This study underscores the effectiveness of CZO nanorod architecture in rapidly detecting CO2 at room temperature, presenting promising avenues for environmental monitoring and sensing applications

Figure 1
Machine-Learning Assisted Micropillar Assay for High-Throughput in-Situ Functional Analysis of Patterned Organoids
Authors: Wu Shuai , Wang Chuanyu , Kang Xuejia , Chen Pengyu
Published: December 2024

Organoids, 3D multicellular tissue structures cultivated in vitro, offer a promising platform for studying organ function and disease. However, traditional techniques for detecting and quantifying protein biomarkers within organoids face challenges in sampling and analysis. Here, we introduce a novel approach utilizing a micropillar-based patch for rapid in vivo sampling and on-pillar quantification of target protein biomarkers in organoids. By employing nanoparticles-antibody conjugates of different sizes and leveraging machine learning-assisted image processing, we achieve multiplex detection of cytokines. This innovative method facilitates minimally invasive biomarker collection and analysis within organoids, potentially enabling point-of-care diagnostics and longitudinal monitoring. Our findings represent a significant step forward in organoid research and hold promise for enhancing our understanding of organ physiology and disease mechanisms.
Chloride Ion Sensing Using Fiber Brag Grating
Authors: Dalgamouni Summer , Benhaddou Driss , Brankovic Stanko
Published: December 2024

Objective of our work is to demonstrate a new approach to chemical sensing. It is based on an optical probe using optical fiber with Brag Grating (FBG) coated with specific metal whose surface is modified to enhance selective adsorption of chemical species (Figure 1A). The goal is to demonstrate a chemical sensor whose transducing mechanism combines two phenomena: First, a light propagation/reflection through an optical fiber with Brag grating having strain dependent dialectic constants. Second, the electrocapillarity of a metal coating which exerts a pressure/strain on the grating dependent on the coverage of adsorbed species. The model system we investigate is sensing of Cl- in aqueous environment. The interest is driven by the critical need for a sensor capable of detecting low levels of chloride ion in the context of dialysis application. Chloride/chlorine is a primary agent used to purify water due to its cost-effectiveness, high reactivity with contaminants, and prolonged decay rate within distribution systems. However, while chlorine is effective at disinfection, its presence in dialysis water can have severe health implications, necessitating its careful monitoring and control. Our data demonstrate path towards the optimum sensor design with specific FBG materials, fiber dimeters and metal coatings selective to Cl- adsorbates(Figure 1B). This sensor provides an ultra-fast, real-time chemical sensing. Experimental data are also supported with full theoretical model i.e. transducer equation. Potential application our work should be of interest for many areas of biomedical engineering and medicine, nuclear reactor technology, high-pressure heat exchangers and turbines, oil and gas sector and military applications.

Figure 1.

(A) Schematics of FBG sensor coated with metal layer discussed in the text. Alternating dielectric layers with different refractive indexes n1 and n2 are indicated and represent the Bragg grating with radius of the fiber R. (B) Shift in the wavelength of Bragg light as a function of chloride concentration in solution of 0.1 M HClO4. Data sets are for two different potentials
of the Au coating. Corresponding different slopes in data sets show dependence of the adsorption constant on the potential of the Au surface
.

Figure 1
(Invited) Materials Development and System Integration for Advanced Gas Sensors
Authors: Zhu Jiadeng , Kayastha Vijaya , Liu Tianyi , Lang Kening , Koch Audra , Landorf Christopher , Younger Steven , Padilla Daniel , Nelson Marriana , Boeser Nickolas , Murray Chandler , Peters Austin , Robledo Christopher , Eldredge Rebecca , Taggart David , Shih Wu-Sheng , Scotch Adam
Published: December 2024

Tremendous progress and achievements have been made over the past decades to advance gas sensor technology, which has been extensively utilized in pollution control and environmental protection. However, designing a robust system integrating various components (i.e., sensor array, substrate, circuit board, connectors, software/hardware, user interface, data collection, etc.) is still a big challenge. In this project, the formulations for each merging analyte (i.e., oxygen, hydrogen, carbon monoxide, carbon dioxide, etc.) have been revisited and well-explored associated with the corresponding advanced characterization approaches, which have been performed to better understand their working mechanisms. More importantly, machine learning (ML) has also been utilized and developed to analyze the collected sensing data, providing accurate and reliable results for actionable decision-making to meet the required criteria. All designs for each component have been further optimized with a goal to achieve a user-friendly system. We hope this work can provide new insights for future gas-sensor development, inspiring more advanced studies and designs in this field.
Fabricated Nanocomposite ZnO-Loaded PVA/PEDOT:PSS Via Electrospinning for Ammonia Detection
Authors: Rakhmanova Aizhan , Soltabayev Baktiyar , Mentbayeva Almagul
Published: December 2024

The problem of air pollution has increased dramatically around the world and there are concerns about the detection of hazardous gases present in the atmosphere as they are very harmful to human health. Remarkably, ammonia (NH3) gas is one of the most hazardous environmental pollutants, contributing to chronic lung disorders and respiratory inflammations. Gas sensors play a crucial role in monitoring and detecting toxic gases, ensuring public safety, preventing food spoilage, and monitoring air quality. Typically, a resistive gas sensor comprises an active sensing material whose electrical conductivity is sensitive to gases. Up to now, lots of work have been related to MOS-based gas sensors. However, MOS-based sensors still face some challenges in selectivity, response/recovery times, and stability. Therefore, this study is dedicated to the investigation of Polyvinyl alcohol (PVA)/Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and ZnO-loaded PVA/PEDOT:PSS electrospun composite nanofibers for gas sensing application. The successful integration of ZnO nanoparticles into the composite polymer matrix was confirmed through a combination of structural, morphological, optical, and thermal analyses, revealing a fibrous structure with enhanced morphology. The gas-sensing study demonstrated the superior performance of the ZnO-loaded fibers in NH3 gas detection, showcasing enhanced sensitivity, selectivity, and long-term stability compared to its pristine counterpart (PVA/PEDOT:PSS). Fabricated sensors showed selectivity and 70 % response to 100 ppm NH3, as well long- term stability for up to 12 months. Our findings not only contribute to the understanding of composite sensor materials but also offers promising candidates for the development of high-performance flexible gas sensors.

Acknowledgment: This work was supported by the Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP23489498). "Development of advanced polymer-based sensor containing biowaste-derived carbon for detection of NH3"

Figure 1
Multi-Marker Biosensor Integrated Explainable AI-Based Cancer Screening System
Authors: Park Sungwook , Park Hyung Joon , Lee Kwan Hyi
Published: December 2024

The Prostate Imaging Reporting and Data System (PI-RADS) score, which is widely used for prostate MRI screening, has established itself as a standard approach for detecting prostate cancer (PCa) due to its reliable diagnostic performance. However, PI-RADS 3 lesions present a significant clinical challenge, as the system delivers only 30 to 40% diagnostic accuracy and is frequently associated with a high rate of false positives. To tackle this issue, we introduce a prostate cancer screening system powered by explainable artificial intelligence (XAI), which incorporates a highly sensitive electrochemical biosensor based on a dual-gate field-effect transistor (DGFET). This innovative system is designed to improve the identification of ambiguous lesions by analyzing the electrochemical sensing profiles of three specific urinary exosomal biomarkers. By generating interpretable results, it allows clinicians to make more confident and evidence-based decisions. Our findings reveal that the XAI-powered PCa screening system achieves impressive diagnostic accuracy, with an area under the curve (AUC) of 0.93, as demonstrated using 102 blinded samples through a non-invasive process. Remarkably, in cases involving PI-RADS 3 lesions, the system more than doubled the diagnostic accuracy compared to traditional PI-RADS scoring methods. Furthermore, the system identified TMEM256 as a crucial biomarker in the accurate diagnosis of PI-RADS 3 lesions, offering clear insight into its decision-making rationale. This study underscores the promise of integrating XAI with electrochemical biosensing to aid healthcare professionals in delivering more informed and evidence-backed diagnoses for prostate cancer, particularly in complex cases.