Nanostructured Catalysts Research Articles

Liquid and gas permeabilities of nanostructured layers: Three-dimensional lattice Boltzmann simulation

Liquid water and gas permeabilities in nanostructured catalyst layers (CLs) (pore size ∼10–150 nm) and microporous layers (MPLs) (pore size ∼50 nm-5 μm) are crucial to reduce the mass transport loss in proton exchange membrane fuel cells (PEMFCs). Experimental measurement of their permeabilities poses great challenges due to their brittle and thin characteristics. Presently, considerable discrepancy exists in the reported permeability values for CLs and MPLs in the literature with variation spanning several orders of magnitude. This study digitally reconstructed various nanostructures of similar pore size as CLs and MPLs to calculate their permeabilities using the Lattice Boltzmann Method (LBM) based on no-slip (e.g. for liquid water flow in MPL and CL's secondary pores) or slip condition (e.g. for gas flow in MPL). Analysis was performed to evaluate the range of pore size in nanostructures for the two boundary conditions. A comprehensive investigation was conducted under various parameters such as the Reynolds number (Re), sphere diameter, porosity, and pore structure. The results revealed that permeability exhibits an increasing trend with the diameter and porosity. The predicted permeability of randomly arranged spheres agrees well with established correlations. The random sphere structure demonstrates higher permeability than their body-centered cubic (BCC) and face-centered cubic (FCC) counterparts. Under slip boundary condition, the permeability was enhanced, compared to the no-slip condition. This study's novelty lies in using distinct boundary conditions to assess the permeabilities of liquid and air, based on flow pattern analysis in the CL and MPL pore structures. A new empirical correlation describing the influence of the Knudsen number (Kn) on the slip permeability was developed, exhibiting consistency with simulation across the entire porosity spectrum.

Catalyst Design and Engineering for CO2-to-Formic Acid Electrosynthesis for a Low-Carbon Economy.

Formic acid (FA) has emerged as a promising candidate for hydrogen energy storage due to its favorable properties such as low toxicity, low flammability, and high volumetric hydrogen storage capacity under ambient conditions. Recent analyses have suggested that FA produced by electrochemical carbon dioxide (CO2) reduction reaction (eCO2RR) using low-carbon electricity exhibits lower fugitive hydrogen (H2) emissions and global warming potential (GWP) during the H2 carrier production, storage and transportation processes compared to those of other alternatives like methanol, methylcyclohexane, and ammonia. eCO2RR to FA can enable industrially relevant current densities without the need for high pressures, high temperatures, or auxiliary hydrogen sources. However, the widespread implementation of eCO2RR to FA is hindered by the requirement for highly stable and selective catalysts. Herein, the aim is to explore and evaluate the potential of catalyst engineering in designing stable and selective nanostructured catalysts that can facilitate economically viable production of FA.

Nitrogen doped TIO2/g-C3N4 nanocatalyst for photodegradation of methylene blue dye

In this study, the ethanol dispersion procedure was implemented to prepare the g-C3N4/N–TiO2 nanocatalyst structure. Sol-gel synthesis is utilized for synthesizing N–TiO2 and g-C3N4 via urea thermal decomposition. Physicochemical properties of produced photocatalysts were revealed using PL imaging, UV–vis DRS, XRD, FTIR, SEM, BET, and TEM. Evaluation of photocatalytic activity of synthetic photocatalysts by exposure to sunlight and degradation of methylene blue (MB) dye. g-C3N4/N–TiO2 NCs showed excellent photocatalytic activity, reaching 96 % MB degradation efficiency in 80 min. g-C3N4 and N–TiO2 doped form a nanocomposite structure that increases photocatalytic activity, affecting charge separation performance and service life. The system also exhibits the ability to collect visible and ultraviolet light. Even after four consecutive cycles, the efficiency of the MB is still above 85 %. Capture experiments showed that the decomposition of MB was mainly caused by h+ and O22− radicals. The results of kinetic investigations indicate that the degradation rate of g-C3N4/N–TiO2 nanocomposites surpasses that of N–TiO2 nanoparticles.

Sensitive detection of persulfate by a novel self-powered electrochemical sensor with carbon cloth electrodes modified with tin-doped cobalt tetroxide.

The accurate and rapid detection of persulfate concentration is important for environmental decontamination and human health protection. In this work, a novel self-powered electrochemical sensor for the sensitive monitoring of persulfate was developed, which utilized cobalt tetroxide (Co3O4@CC) or tin-doped cobalt tetroxide (SnxCo3-xO4@CC) cathode as the sensing element and anode with electrogenic microorganisms as the power supplier. The Co3O4@CC and SnxCo3-xO4@CC electrodes were fabricated by in situ growing nanostructured Co3O4 or SnxCo3-xO4 catalysts on carbon cloth. Electrochemical tests revealed that these electrodes exhibited excellent catalytic reduction performance toward persulfate because of the synergistic catalysis by Co3O4 and electrode electrons, well-exposed Co2+/Co3+ catalytic sites, and high electron transfer efficiency. Tin doping could enhance the catalytic persulfate reduction by improving the conductivity and electron transfer of the Co3O4 catalyst. The electrode prepared at a hydrothermal temperature of 90°C and a tin dosage of 0.286g·cm-2 achieved the highest persulfate reduction activity under pH 7. The sensing properties of the self-powered sensors toward persulfate were explored in detail. Results showed that under the optimal external load of 300 Ω, the proposed sensor could display a broad detection range of 0 to 1500μmol L-1 K2S2O8 with sensitivities of 1.13 and 0.12 μA μmol-1 L, a detection limit of 1.11μmol L-1 (S/N = 3), and a fast response time within 30s. The sensors also presented satisfactory reproducibility and selectivity during the detection of persulfate. The proposed sensor will provide a new approach for sensitive, on-site, and real-time monitoring of persulfate for a wide range of applications.

Enhancement of visible light adsorption and photocatalytic degradation activity of organic dye by coating semiconducting TiO2 shell on plasmonic Au particles

The plasmonic effect enhances light absorption in semiconductor photocatalysts, while the noble metal-semiconductor interface promotes charge carrier transfer and separation, boosting photocatalytic activity. However, current methods for synthesizing metal-core TiO2-shell nanoparticles face challenges, such as keeping stable and preventing aggregation. This study presents a simple and moderate synthesis method for Au@TiO2 core-shell nanoparticles, enabling precise control over the TiO2 shell thickness and stable photocatalytic performance. Various characterization techniques were employed to assess the optical and structural properties of the synthesized Au@TiO2 core-shell nanostructures. The results demonstrated that increasing the Au core concentration led to a gradual decrease in TiO2 shell thickness. The adsorption properties and photocatalytic degradation efficiency of the synthesized Au@TiO2 core-shell nanostructured catalysts were thoroughly examined, particularly focusing on their performance with methyl orange (MO) and methylene blue (MB). Au@TiO2 achieved excellent adsorption performance for MO, with a maximum capacity of 231±6 mg/g. Furthermore, Au@TiO2 exhibited higher photocatalytic degradation activity of both MO and MB than pure TiO2. The mechanism study indicated that it attributed to enhanced visible light absorption, reduced bandgap, and higher valence band energy. Additionally, the Au@TiO2 catalysts showed good cyclic stability, making them promising for future applications. This research offers insights into designing efficient photocatalysts, addressing existing synthesis challenges, and contributing valuable references for future advancements.

Silver Nanowire Aerogel Support Promotes Stable Hydrogen Evolution Reaction at High Current Density.

The stability of electrocatalysts during the hydrogen evolution reaction (HER) is vital for efficient production of hydrogen energy. Herein, we demonstrate that silver nanowire aerogel-based support (AABS) could facilitate the construction of HER catalysts with extraordinary long-term stability. A full nanostructure catalyst of nickel phosphide based formed on AABS (Ni2P-Ni5P4@AABS) was prepared to achieve an overpotential of 687 mV (without iR compensation) for HER at the current density of 1 A cm-2 in 0.5 M H2SO4. Excitingly, the stable HER performance was kept for 42 days during the long-term stability (i-t) test at high current density (0.5-1 A cm-2). The excellent HER performance of the Ni2P-Ni5P4@AABS catalyst is attributed to rapid electron transport pathways, numerous more accessible active sites, and support induced enhanced catalytic activity. The support effect was highlighted by a proposed phenomenological two-channel model for electron transport, which provides fresh insights into the design strategy for energy storage and delivery.

Role of Structural and Compositional Changes of Cu2O Nanocubes in Nitrate Electroreduction to Ammonia.

Nitrate electroreduction reaction (NO3RR) to ammonia (NH3) still faces fundamental and technological challenges. While Cu-based catalysts have been widely explored, their activity and stability relationship are still not fully understood. Here, we systematically monitored the dynamic alterations in the chemical and morphological characteristics of Cu2O nanocubes (NCs) during NO3RR in an alkaline electrolyte. In 1 h of electrolysis from -0.10 to -0.60 V vs RHE, the electrocatalyst achieved the maximum NH3 faradaic efficiency (FE) and yield rate at -0.3 V (94% and 149 μmol h-1 cm-2, respectively). Similar efficiency could be found at a lower overpotential (-0.20 V vs RHE) in long-term electrolysis. At -0.20 V vs RHE, the catalyst FE increased from 73% in the first 2 h to ∼90% in 10 h of electrolysis. Electron microscopy revealed the loss of the cubic shape with the formation of sintered domains. In situ Raman, X-ray diffraction (XRD), and in situ Cu K-edge X-ray absorption near-edge spectroscopy (XANES) indicated the reduction of Cu2O to oxide-derived Cu0 (OD-Cu). Nevertheless, a remaining Cu2O phase was noticed after 1 h of electrolysis at -0.3 V vs RHE. This observation indicates that the activity and selectivity of the initially well-defined Cu2O NCs are not solely dependent on the initial structure. Instead, it underscores the emergence of an OD-Cu-rich surface, evolving from near-surface to underlying layers over time and playing a crucial role in the reaction pathways. By employing online differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared spectroscopy (FTIR), we experimentally probed the presence of key intermediates (NO and NH2OH) and byproducts of NO3RR (N2 and N2H x ) for NH3 formation. These results show a complex relationship between activity and stability of the nanostructured Cu2O oxide catalyst for NO3RR.

Engineering potential electrocatalysts for both AEM Electrolyzers and Redox Flow Batteries: Design of experiments at the different scales

Both water electrolysis and electrochemical energy storage are promising technologies for dealing with the intermittency of green electricity generation. In this work we investigated the possibility of using the same electro-catalyst for hydrogen production by Anion Exchange Membrane Water Electrolysis (AEMWE) and energy storage by Redox Flow Batteries (RFB). A complete experimental campaign was designed to investigate the effects of the catalyst nanostructure and morphology on the electrode performance at different scales. Focus was devoted to the choice of the main factors influencing the catalyst structure, its morphology and electrochemical activity; taking further into account the technique to deposit the catalyst on the Gas Diffusion Layer (GDL) and its integration inside the Membrane Electrode Assembly (MEA). Some results are reported for a spinel-based NiCo2O4 catalyst, chosen as a base nanocomposite to develop more complex materials for both the Oxygen Evolution Reaction (OER) in AEMWE and the positive electrode in Vanadium RFB in the future.

High-strength TiO2/TPU composite fiber based textiles for organic pollutant removal

Effective integration of nanostructured photocatalysts into polymer matrices is crucial for the broad practical application of fiber-based photocatalytic composite textiles. Herein, highly durable TiO2/TPU composite fibers with high TiO2 content (>30 wt. %) were prepared through wet spinning using 1D electrospun TiO2 nanofibers (TNFs). Due to the fiber reinforcement principle, the TNF/TPU composite fibers exhibited superior mechanical properties compared with pure TPU fibers. Furthermore, the TNF/TPU composite fibers with a ratio of 1:2 process impressive degradation efficiency for rhodamine B (RhB). The orientation of 1D TNFs and stronger interface between TNF and TPU matrices not only enable the excellent load sharing and transfer effects following fiber pullout and crack bridging mechanisms, but also improve photogenerated charge transfer efficiency, resulting in high strength and high photocatalytic activity. In addition, enhanced TNF exposure on the fiber is due to the hollow and porous structures of composite fibers, which is advantageous for photocatalytic degradation. Notably, when the RhB concentration exceeded 15 ppm, the TNF/TPU composite fibers exhibited higher degradation efficiency than the TNF powder. Therefore, TNF/TPU composite fiber–based textiles with high photocatalytic activity and strength are promising for overcoming the separation and recovery issues of nanostructured catalysts in practical wastewater treatment applications.

Conductive Polymer Hydrogel-Derived 3D Nanostructures for Energy and Environmental Electrocatalysis.

Renewable energy and advanced water treatment technologies hold profound significance for driving sustainable development in modern society. Given the environmental friendliness and high efficiency of electrocatalysis processes, great expectations are placed on their applications in energy and water-related fields. However, the electrocatalysis is limited by the selectivity, activity, and durability of the electrocatalytic reactions. Hydrogels, with their hierarchical porous structure, compositional and structural tunability, and ease of functionalization, are bringing surprising advances in advanced energy and environment. Hydrogel catalysts, inheriting the advantages of hydrogel materials, hold promise for achieving significant breakthroughs in electrochemical performance. Here, the latest advancements in energy and environmental electrocatalytic fields are summarized based on the 3D nanostructured hydrogel catalysts. In addition, future potentials and challenges of continuing research on hydrogel materials for energy and environment are discussed.

Investigation of hydrogen storage properties on the Mg-La-Ni alloy compounded with C@Pr2O3 composite catalyst

To explore the effect of C@Pr2O3 on the hydrogen storage performance of Mg-La-Ni alloy. In experiment, a nanostructured composite catalyst C@Pr2O3 was prepared using chemical blowing carbonization. The microstructures of the catalyst and alloy powder were characterized using techniques such as transmission electron microscope, high-resolution transmission electron microscopy, scanning electron microscope, and selective region electron diffraction. Hydrogen storage properties of the alloy were evaluated using Pressure-composition-temperature equipment, and it was observed that the addition of the catalyst significantly enhanced the hydrogen kinetics of the alloys. At 320 ℃, the two-minute hydrogen saturation ratio of Mg96NiLa3 +5 wt% C@Pr2O3 was 80.65 %, Mg96NiLa3 +7 wt% C@Pr2O3 releases 3 wt% H2 at 340 °C for 6 min. This can be attributed to the addition of nanoscale C and catalyst Pr2O3, which improved the hydrogen kinetics of the alloys. The dehydrogenation activation of Mg96NiLa3 +5 wt%C@Pr2O3 is 85.2 kJ/mol, enhancing the rate of hydrogen release while simultaneously reducing the activation energy required for dehydrogenation of the alloy. The enthalpy of hydrogen absorption of Mg96NiLa3 +5 wt% C@Pr2O3 was 72 KJ/mol. However, the thermodynamic properties of the alloy were still not satisfied with the requirements of practical application.

Recent progress in high‐entropy nanocatalysts

AbstractHigh‐entropy alloys (HEAs) are a promising group of materials composed of multiple elements (≥5) in nearly equal proportions (5 at%–35 at%), which exhibit uniformly mixed compositions and highly stable crystal structures and offer a wide range of design possibilities, making them exceptionally stable, multifunctional, and suitable for various applications. Recent research studies have identified the potential of HEAs as catalysts for electrocatalytic reactions, focusing on adjustable stress environments, optimizable d‐band centers, and high conformational entropy. Understanding the interactions among constituent elements, alloy formation, and catalytic reaction mechanisms is essential for optimizing HEAs' catalytic performance. This comprehensive review delves into the historical context, defining characteristics, and underlying significance of HEAs development. It also examines four primary effects of HEAs (high‐entropy effect, lattice distortion, sluggish diffusion, and cocktail effect) and their relevance to catalyst design criteria (selectivity, activity, stability, and cost). Additionally, it summarizes recent advances in nanostructured HEA catalyst synthesis, highlighting their advantages and challenges and explores the use of HEAs in electrocatalytic redox reactions involving small molecules (H, C, O, N). The paper underscores the importance of integrating experimental methods and theoretical calculations to design, synthesize, and understand alloy–property relationships of HEAs, emphasizing their vast potential for catalytic applications.

Enhancement of magnesium aluminate-based nickel and cobalt nanostructured catalysts with iron for improved performance in carbon dioxide methanation

This study investigates the performance of Ni and Co catalysts based on Fe-promoted MgAl2O4 for CO2 methanation, which is a crucial step in mitigating environmental carbon dioxide levels. The MgAl2O4 support was modified with various Fe loading (5, 10, and 15 ​wt%) and fabricated via a novel coprecipitation technique with the help of ultrasonic waves and chosen as support for 15 ​wt% Ni and Co active phases. Examination of the BET surface properties of the catalysts showed an increase in surface area in the range of 54–82 ​m2/g and 73–85 ​m2/g with an increasing Fe loading for Ni and Co catalysts, respectively. Among the Ni-based catalysts, the 15Ni/10FeMgAl2O4 specimen exhibited the best performance (with a 73.31 ​% CO2 conversion and 95.61 ​% selectivity rate) and remarkable lifetime during 10 ​h at 400 ​°C due to the better reducibility and the increase in hydrogen consumption. However, a rise in Fe amount to 15 ​wt% led to a reduction in the CO2 conversion to 34.43 ​%. The catalytic outcomes also demonstrated that the presence of Fe in Co/MgAl2O4 catalysts negatively affects catalytic performance. The unpromoted Co/MgAl2O4 sample demonstrated the best performance, achieving a conversion rate of 52.41 ​% at 350 ​°C.

Rapid fabrication of Ni supported MgO-ZrO2 catalysts via solution combustion synthesis for steam reforming of methane for hydrogen production

In this study, we introduced a solution combustion as a simple, efficient, and rapid technique for synthesis of a nanostructured Ni catalyst supported on MgO-ZrO2 for hydrogen production by steam reforming of methane. A series of Ni/MgO-ZrO2 catalysts with different Ni contents were prepared and investigated to observe a suitable Ni loading content. The evaluation of catalytic performance of the as-prepared catalysts was performed in a packed-bed reactor at 700 °C and atmospheric pressure at steam to carbon ratio (S/C) of 2. As a result, the 20Ni/20MgO-ZrO2 catalyst exhibited not only outstanding catalytic performances, but also minimized coke deposits, attributed to the presence of oxygen vacancies of MgO-ZrO2 solid solution. In addition, combustion synthesis could result in formation of NiO-MgO solid solution, boosting uniform dispersion of Ni particles. A durability test of the optimized 20Ni/20MgO-ZrO2 catalyst was conducted at 700 °C for 50 h, revealing a near constant methane conversion of approximately 92.9%. Although filamentous carbon and carbon encapsulation were observed on the surface of spent catalyst, there is no significant negative impact on the steam reforming performance. In conclusion, this present work highlights the efficacy of the solution combustion method for synthesis of nanostructured Ni/MgO-ZrO2 catalysts with superior catalytic performance and less coke deposits for hydrogen production from methane steam reforming.

Morphology Variation of Ternary PdCuSn Nanocrystalline Assemblies and Their Electrocatalytic Oxidation of Alcohols.

Metal alloys not only increase the composition and spatial distribution of elements but also provide the opportunity to adjust their physicochemical properties. Recently, multimetallic alloy nanocatalysts have attracted great attention in energy applications and the chemical industry. This work presents the production of three ternary PdCuSn nanocrystalline assemblies with similar compositions via a one-step hydrothermal method. The shape variation of assembly units from nanosheets and nanowires to nanoparticles were realized by adjusting the percentage of Sn in metal precursors. Experimental data show that PdCuSn nanowire networks showed the best catalytic activity by virtue of their optimized morphological characteristics and microscopic electronic structure. With electrooxidation of methanol, ethanol, ethylene glycol, and glycerol at 30 °C, PdCuSn nanowire networks demonstrated catalytic activity of 1129, 2111, 2540, and 1445 mA mg-1, respectively. The catalytic activity for alcohol oxidation is attributed to the production of the electronic structure and morphology features that are most suitable. This is achieved by introducing the proper quantities of Cu and Sn components in the first stage of synthesis. This study would help with the construction of high-efficiency nanostructured alloy catalysts by regulating the electronic structure and morphology.

Atomically Engineered Defect-Rich Palladium Metallene for High-Performance Alkaline Oxygen Reduction Electrocatalysis.

Defect engineering is a key chemical tool to modulate the electronic structure and reactivity of nanostructured catalysts. Here, it is reported how targeted introduction of defect sites in a 2D palladium metallene nanostructure results in a highly active catalyst for the alkaline oxygen reduction reaction (ORR). A defect-rich WOx and MoOx modified Pd metallene (denoted: D-Pd M) is synthesized by a facile and scalable approach. Detailed structural analyses reveal the presence of three distinct atomic-level defects, that are pores, concave surfaces, and surface-anchored individual WOx and MoOx sites. Mechanistic studies reveal that these defects result in excellent catalytic ORR activity (half-wave potential 0.93V vs. RHE, mass activity 1.3AmgPd-1 at 0.9 V vs. RHE), outperforming the commercial references Pt/C and Pd/C by factors of ≈7 and ≈4, respectively. The practical usage of the compound is demonstrated by integration into a custom-built Zn-air battery. At low D-Pd M loading (26µgPdcm-2), the system achieves high specific capacity (809mAhgZn -1) and shows excellent discharge potential stability. This study therefore provides a blueprint for the molecular design of defect sites in 2D metallene nanostructures for advanced energy technology applications.

Pulsed laser processed FeSiBCuNb glassy alloy with polyphasic nanostructure interactions for efficient degradation of reactive red 195 via photoactivating persulfate

An Fe73.5Si13.5B9Cu1Nb3 amorphous ribbon was used as a precursor to fabricate biphasic and polyphasic nanostructure catalysts via pulsed laser processing. The enhancement in nanostructure heterogeneity, light absorption ability, surface hydrophilicity and photothermal conversion of the catalyst resulted in improving photocatalytic performance, evidenced by a higher k value, increased total organic carbon removal rate, and lower ΔE value. The degradation pathway of reactive red 195 molecules in the persulfate system was proposed. Density-functional theory simulations indicated that the excellent catalytic performance of the pulsed laser catalyst was due to its unique polyphasic nanostructure, which induced the reduction in the energy barrier of the rate-determining step (from 2.74 to 1.34 eV) during the conversion of S2O82− to SO4−•. The processed catalyst exhibited an ultrahigh catalytic ability of kSA•C0 = 7733 mg·m−2·min−1 and strong reusability (28 cycles) without efficiency decay. This study revealed that regulating the nanostructure of the catalyst is an effective strategy to achieve high photocatalytic performance.

Investigating metal (M = Mn, Fe, and Ni)-doped Co(OH)2 nanofibers for electrocatalytic oxygen evolution and electrochemical biosensing performance.

To achieve efficient and cost-effective electrochemical water splitting, highly active and affordable nanostructured catalysts are the key requirement. The current study presents the investigations of the efficacy of metal (Mn, Fe and Ni)-doped Co(OH)2 nanofibers towards oxygen evolution via water splitting. Notably, Ni-doped Co(OH)2 demonstrates superior OER performance in KOH electrolyte, surpassing standard IrO2 with a modest potential of 1.62 V at 10 mA cm-2. The remarkable activity is attributed to the nanofiber structure, facilitating faster conduction and offering readily available active sites. Ni-doped Co(OH)2 nanofibers displayed enduring stability even after 1000 cycles. This work underscores the importance of transition-metal based catalysts as effective electrocatalysts, providing the groundwork for the development of cutting-edge catalysts. Additionally, the electrochemical sensing capability towards ascorbic acid is evaluated, with Ni-doped Co(OH)2 showing the most promising response, characterized by the lowest LOD and LOQ values. These findings highlight the potential of Ni-doped Co(OH)2 nanofibers for upcoming diagnostic detection devices.

Accelerated Discovery of Multi-Metallic Nanostructured Catalysts for Anion Exchange Membrane Water Electrolyzers: Oxygen Evolution Reaction

The current reliance on platinum group metals (PGMs) as electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) water electrolyzers, the current industry standard, presents a significant barrier to the widespread adoption of hydrogen as a clean energy carrier. The scarcity and high cost of PGMs necessitate the development of alternative materials and technologies that offer comparable performance at a reduced cost. In this context, anion exchange membrane (AEM) water electrolyzers have emerged as a promising alternative.This presentation addresses this imperative by focusing on the design and synthesis of nanostructured mesoporous multi-metallic catalysts for AEM water electrolyzers, leveraging earth-abundant materials as alternatives to the rare and expensive PGMs currently employed in PEM water electrolyzers. Transition metal oxides, sulfides, and phosphides are promising candidates to replace PGMs, given their abundance, low cost, and tunable catalytic properties conducive to high OER activity. The OER activity and durability of newly developed multi-metallic transition metal catalysts in an alkaline environment will be discussed in this presentation.Preliminary results demonstrate that the developed catalysts exhibit high OER activity, achieving a potential of <1.5 V versus RHE at a current density of 10 mA cm⁻² in 1.0 M KOH. Notably, this surpasses the performance of commercial OER catalysts in alkaline environments. Furthermore, the catalyst exhibits superior durability, with < 0.5 mV/h potential loss over 100 h durability test at 10 mA cm⁻² in 1.0 M KOH.AcknowledgmentsThis work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). Argonne is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, under Contract DE-AC-02-06CH11357 .

Quantification of Hydrogen and Transition Metals in the Cathode Catalyst Layer of Anion Exchange Membrane Electrolyzer By Ion Beam Techniques

Anion Exchange Membrane Water Electrolyzer (AEMWE) has increased interest in H2 production at low cost and high scalability. The efficiency is strongly dependent on the membrane electrode assembly (MEA) with appropriate ionomer and catalyst layers. Herein, we report AEMWE with MoNi4-MoO2 cathode catalyst layer in ionomer-free Catalyst Coated Substrate (CCS) configuration. The optimized MEA for AEMWE demonstrated the superior performance of 225 mA/cm2 at 2V with more than 48 hours of durability. The X-ray diffraction confirmed the NiMoO4 phase transformation to MoNi4-MoO2 and SEM-EDS was used to study the morphology and elemental composition of the deposited catalyst. X-ray photoelectron Spectroscopy demonstrated the dominant metallic MoO2 formed after H2/Ar annealing. Rutherford Backscattering Spectroscopy (RBS) was also employed to measure the depth composition profile of the catalyst layer exhibiting the reduction of Ni concentration in the bulk after annealing. Further, we introduce hydrogen depth profiling by Nuclear Reaction Analysis (NRA) via the resonant 1H(15N,αγ)12C reaction as a versatile method for the highly depth-resolved visualization of hydrogen(H) in the near-surface region, including transitions of hydrogen between the surface and the bulk, and between shallow interfaces of the nanostructured cathode catalyst layer. The diffusion of the H atoms was observed with a 40% atomic percent of Hydrogen after H2/Ar annealing of the catalyst for 180 minutes (about 3 hours) and decreased to 10% atomic percent of hydrogen after 24 hours of electrolyzer operation. This technique also enabled the measurement of the zero-point vibrational energy of hydrogen atoms absorbed on the surfaces of the catalyst layer. Overall, this work better explains the cathode catalyst degradation effects and hydrogen diffusion in the cathode catalyst layer responsible for voltage and mass transfer losses in AEM electrolyzers.