Catalyst-support Interactions Research Articles

Synergistic Chemisorption and Electrocatalysis of MoO2 Nanoparticles/Carbon Nanosheets with Strong Catalyst-Support Interactions for High Performance Lithium-Sulfur Batteries

Synergistic Chemisorption and Electrocatalysis of MoO2 Nanoparticles/Carbon Nanosheets with Strong Catalyst-Support Interactions for High Performance Lithium-Sulfur Batteries

Acid-enabled carbon cloth boosts activity and durability of Au/Co3O4 catalysts for acidic water electrolysis

Abstract The advancement of efficient and durable electrocatalysts is crucial for enhancing overall water-splitting technologies, particularly in harsh acidic environments. In this work, we treated carbon cloth (CC) with a mixture of HNO3 and H2SO4 to improve its surface properties and use it as a substrate for depositing Au/Co3O4 catalysts. The acid-treated CC (TCC) exhibited enhanced hydrophilicity due to the introduction of increased hydroxyl and carboxyl functional groups, leading to a higher loading of the Au/Co3O4 catalyst (3.36 wt% Co and 1.42 wt% Au) combined with uniform morphology compared to the untreated CC. The resulting Au/Co3O4/TCC catalyst demonstrated several desirable characteristics, including a higher specific surface area of 40.5 m2 g−1 and smaller charge transfer resistance. When employed as a bifunctional electrocatalyst for overall water splitting, the Au/Co3O4/TCC exhibited a low cell voltage of 1.62 V in 0.5 M H2SO4 electrolyte and outstanding durability, maintaining its performance over 24 h at a current density of 10 mA cm−2 without significant degradation, attributed to the strong interfacial interaction between the catalyst and the substrate. The enhanced wettability, surface area, and catalyst-support interaction arising from the acid treatment of the carbon cloth substrate were the key factors enabling the superior electrochemical performance of the Au/Co3O4/TCC catalyst system.

Metal-Organic Framework-Templated Synthesis of Nickel-Alumina Nanocatalysts Improves Catalyst-Support Interaction for Higher Activity and Stability in Biogas Reforming under Controlled Oxidizing Conditions.

Tri-reforming methane with CO2, O2, and H2O mixtures requires a delicate balance of dry-reforming, partial oxidation, and steam-reforming reactions to improve the CO2 conversion and H2/CO ratio. Nickel-alumina has been reported before for the tri-reforming of methane, although at higher temperatures (>900 °C). This is because the current approaches for nickel-alumina synthesis are ineffective in generating stronger catalyst-support interactions necessary to maintain higher active sites and stall carbon nanotube (CNT) deposition. Here, we report a synthesis method that allows controlled loading of nickel on alumina-based MIL-53 metal-organic framework followed by calcination to generate 2.5-10 wt % nickel nanoparticles dispersed on alumina. The 5 wt % nickel-alumina mixtures resulted in nanometer-sized crystallites, better metal dispersion, and more active sites for enhanced catalytic activity. This optimal loading of nickel allows stronger interaction with alumina for over 100 h of stable performance of tri-reforming at 800 °C, achieving ∼98% CH4 conversion, ∼36% CO2 conversion, and no carbon deposition while producing Fischer-Tropsch-ready feed containing a H2/CO ratio of 3.2.

Oxygen Evolution Catalysts with Iridium Oxide Supported on Doped Titanium Oxide: Role of Dopants on Catalysts Reactivity and Stability

Titanium dioxide (TiO2) is a semiconductor that has been extensively studied for its thermo and photo catalytic properties due to its high stability, abundant oxygen vacancies and low price. In electrochemistry, titanium dioxide has been used as support for anode catalysts in Proton Exchange Membrane Water Electrolysis (PEMWE). The electrolysis of water into oxygen and hydrogen is kinetically limited by the Oxygen Evolution Reaction (OER) occurring at the positive electrode with a four-electron transfer. The noble metal oxides of Ruthenium and Iridium are currently considered the best electrocatalysts for OER due to their high activity and relatively high IrO2 stability [1]. The high price and scarcity of these precious catalysts prompt a strong interest in minimizing their loading [2]. The use of an electronically conductive support allows to decrease the loading by increasing the surface to volume ratio of precious metal particles. Titania is highly stable at the high potentials used during the OER and can be made conductive using some transition metals as dopants [3].TiO2 exists in nature in three crystalline forms: rutile, anatase, and brookite but because iridium oxide is used for OER in its rutile phase, and to promote epitaxial growth, this work uses the doped-TiO2 rutile phase as a support for Iridium oxide catalysts.New synthetic routes based on sol-gel process are used to form (Ru, Nb, Ta)-TiO2 nanoparticles. The size, shape and crystalline structure of the support was controlled by tuning calcination temperature and the Ti precursor. The doped rutile TiO2 particles synthesized consist of an ideal support for iridium oxide nanoparticles deposited by wet impregnation in different loading and phase. The epitaxial growth from rutile TiO2 to rutile IrOx promotes the catalyst support interaction and electrical conductivity.All the catalysts were characterized by their physico-chemical and electrochemical properties towards the oxygen evolution reaction. The surface morphology and crystallinity of these materials was evaluated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity toward oxygen evolution reaction was investigated in liquid electrolyte in a 3-electrode set-up. [1] Alia, S. M.; Rasimick, B.; Ngo, C.; Neyerlin, K. C.; Kocha, S. S.; Pylypenko, S.; Xu, H.; Pivovar, B. S. Activity and Durability of Iridium Nanoparticles in the Oxygen Evolution Reaction. J. Electrochem. Soc 163, 596-603 (2016) [2] Carmo, M.; Fritz, D. L.; Mergel, J.; Stolten, D. A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 38, 4901– 4934 (2013) [3] Bauerfeind, K.C.L.; Laun, J., Frisch, M.; et al. Metal Substitution in Rutile TiO2: Segregation Energy and Conductivity. J. Electron. Mater. 51, 609–620 (2022)

(Invited) Development of High Entropy Catalysts for Efficient Electrochemical Fuel Production

Electrochemical fuel production methods, such as water splitting, ammonia, and synthetic hydrocarbon production, are at the forefront of sustainable energy resource development. However, the journey to commercialization is fraught with obstacles, particularly in creating active and stable electrocatalysts. This is a critical area of study, as these catalysts are the foundation of electrochemical water splitting for H2 production, nitrogen (NRR) and nitrate (NitRR) reduction reactions for ammonia production and CO2 reduction reaction (CO2RR) for synthetic hydrocarbon synthesis. Therefore, pursuing higher metal utilization efficiency and developing non-precious elements-based catalysts are crucial to ensure the feasibility of cost-effective hydrogen production systems. High entropy catalysts (HEC) with five or more metals are solid solution alloys with unique structures and electrochemical properties. The noble and non-noble metal-based HEC design strategy with strong metal support interaction (SMSI) and porous surfaces amplifies the extrinsic electrocatalytic activity, ensuring high durability over harsh electrochemical conditions for low maintenance and cost-efficiency. The main challenge lies in enhancing their extrinsic activity via catalyst-support interactions for efficient electrochemical reactions. To address this significant and persistent technical barrier, our research is focused on the intensive search for efficient, durable, and inexpensive HEC with high solar energy conversion efficiency for efficient electrochemical water splitting, hydrocarbon conversion reaction, and electrochemical ammonia production processes, thereby making a substantial contribution to the field of sustainable energy resources. Figure 1

Reactivity and Stability of Reduced Ir-Weight TiO2-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes.

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO2-supported Ir@IrO(OH)x core-shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO2-supported Ir@IrO(OH)x core-shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A gIr-1 at 1.53 VRHE while reducing the iridium packing density from 1.6 to below 0.77 gIr cm-3. These advancements allow for viable anode layer thicknesses with lower Ir loading, reducing iridium utilization at 70% LHV from 0.42 to 0.075 gIr kW-1 compared to commercial IrO2/TiO2. The identification of the Ir@IrO(OH)x/TiO2 OER catalyst resulted from extensive HAADF-EDX microscopic analysis, operando XAS, and online ICP-MS analysis of 30-80 wt % Ir/TiO2 materials. These analyses established correlations among Ir weight loading, electrode electrical conductivity, electrochemical stability, and Ir mass-based OER activity. The activated Ir@IrO(OH)x/TiO2 catalyst-support system demonstrated an exceptionally stable morphology of supported core-shell particles, suggesting strong catalyst-support interactions (CSIs) between nanoparticles and crystalline oxide facets. Operando XAS analysis revealed the reversible evolution of significantly contracted Ir-O bond motifs with enhanced covalent character, conducive to the formation of catalytically active electrophilic OI- ligand species. These findings indicate that atomic Ir surface dissolution generates Ir lattice vacancies, facilitating the emergence of electrophilic OI- species under OER conditions, while CSIs promote the reversible contraction of Ir-O distances, reforming electrophilic OI- and enhancing both catalytic activity and stability.

Research Progress of High-entropy Oxides for Electrocatalytic Oxygen Evolution Reaction.

High-entropy oxides (HEOs), similar to high-entropy materials (HEMs), have "four-core effects", i. e., high-entropy effect, delayed diffusion effect, lattice distortion effect and cocktail effect, which have attracted more and more attention in the scientific field of renewable energy technology due to their unique structural characteristics, variable chemical composition and corresponding functional properties. HEOs have become potential candidates for electrocatalytic oxygen evolution reaction (OER), which is a key half reaction for electrolytic CO2, nitrogen reduction, and water electrolysis. However, the precise synthesis of HEOs with a wide range of components and structures is challenging, not to mention their active and stable operation for OER. In this paper, we review the recent advancements in the electrocatalytic oxygen evolution facilitated by HEOs in water electrolysis. We analyze these developments from the perspectives of activity and stability in acid and alkaline conditions, respectively. Furthermore, we summarize the design from the aspect of element composition, structure, morphology, and catalyst-support interactions, along with related reaction mechanism of HEOs. Additionally, we discuss the current challenges faced by HEOs in the field of OER and suggest potential directions for the future development of HEOs beyond water electrolysis application.

Catalyst–Support Interaction in Polyaniline-Supported Ni3Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn-Air Batteries

HighlightsNi3Fe oxide, with an average size of 3.5 ± 1.5 nm, was successfully deposited onto polyaniline (PANI) support through a solvothermal strategy followed by calcination.The catalyst–support interaction between Ni3Fe oxide and PANI can enhance the Ni-O covalency via the interfacial Ni-N bond.Ni3Fe oxide/PANI-assembled Zn-air batteries achieve superior cycling life for over 400 h at 10 mA cm−2 and a low charge potential of around 1.95 V.

Advancing Catalyst Performance in Electrochemical Water Splitting

The transition to renewable energy, vital for a sustainable future, frequently encounters challenges such as low energy density and intermittency. A promising solution lies in converting renewable energy into chemical bonds, notably hydrogen, through electrochemical water splitting. This process, however, is hindered by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Consequently, this necessitates the use of rare and expensive iridium-based catalysts. Given that iridium is the only metal resilient enough to withstand the harsh anodic conditions of OER, reliance on it poses significant economic challenges, making water electrolysis less competitive compared to fossil fuel-based technologies.In response to these challenges, our research has two main objectives. First, we aim to understand the often observed trade-off between iridium OER activity and stability. (1) Second, we intent to enhance our understanding of catalyst-support interactions by explore the use of conductive and potentially durable materials as supports for iridium to improve efficiency, a critical yet largely unexplored area.To achieve these goals, we employ advanced techniques, including inductively coupled plasma mass spectrometry coupled with scanning flow cell. This method enables us to perform detailed potential and time-resolved stability analyses.Specifically, we conduct an in-depth investigation of the impact of pH across a range from acidic to alkaline environments. Furthermore, we explore a variety of backing electrodes, investigate accelerated stress tests (AST) parameters, (2) and assessing how catalyst loading and Nafion content affect the performance and stability of iridium catalysts.Our findings provide a deeper understanding of iridium’s stability during OER and highlight the importance of catalyst-support interactions. (3, 4) By addressing the key challenges associated with iridium-based catalysts, this knowledge is crucial for the development of more cost-effective catalysts with minimized use and hence sustainable water electrolysis technologies, marking a step closer to realizing more efficient and economically viable methods for harnessing and storing renewable energy.

Value-Added Electrolysis Hydrogen Production Via Methanol Oxidation over a Synergetic Pt1-W Dual-Site Catalyst

Electrochemical water splitting is a promising way of generating hydrogen for future sustainable green energy source technology options to replace nonrenewable and environmentally pollutant hydrocarbon energy sources. However, due to its high overpotential in oxygen evolution reaction (OER) and low-value product O2, some candidate anodic reactions with low potential should be proposed to replace OER, such as alcohol oxidation. Unlike fuel cell applications, partial oxidation is preferred to achieve high-value products rather than complete oxidation. For this purpose, we design a synergistic effect Pt1-W site on the dual-doped TiO2 support (Ti0.8W0.2NxOy) to catalyze alkaline methanol oxidation and gain 90% selectivity of formate production. Comparing the case of the Pt nanoparticles (69% selectivity of formaldehyde), the Pt single-atom catalyst controls selectivity and enhances the reactivity and stability attributed to the strong catalyst-support interaction. As a result, this work shows a novel strategy for electrochemical hydrogen production at far lower anodic potential by designing a stable and efficient Pt-based single-atom catalyst.

Probing Charge Transfer across Various Metal Support Interactions in Heterogeneous Catalysts via 4D-STEM Techniques

Probing Charge Transfer across Various Metal Support Interactions in Heterogeneous Catalysts via 4D-STEM Techniques

High performance nickel structured catalysts prepared using EDTA for hydrogen production

Bioethanol Steam Reforming is a sustainable and environmentally friendly way to produce hydrogen. The most promising catalysts for this reaction are deactivated by carbon deposition and sintering. It is well known that the synthesis method can affect the active phase dispersion and metal‒support interactions in catalysts. In this work, structured systems based on Ni/CeO2–MgAl2O4 were prepared by using ethylenediaminetetraacetic acid, EDTA, for Ni incorporation. An EDTA‒free structured system was also prepared, for comparison. FeCrAlloy metal monoliths were used as support, as they provide efficient heat transfer due to their high thermal conductivity. The catalysts were evaluated in the ethanol steam reforming reaction at 650 °C. The Ni precursor influences the properties and catalytic performance of the systems. The systems prepared from [Ni(EDTA)]2- complex showed good reaction performance during 25 h (5.3 and 5.7 mol H2/mol C2H5OH for systems containing 1 and 5 wt% of Ni). The EDTA‒free system showed low activity. The best performing system was subjected to a regeneration process and evaluated in a second reaction cycle, showing good performance. Finally, the best structured system was compared with a powder catalyst. The results reflect that the performance of the monolithic reactor is significantly higher than the packed bed reactor.

Operando X-ray Absorption Spectroscopy as a Powerful Tool for Uncovering Property-Activity Relationships for Oxygen Evolution Transition Metal Oxide Catalysts.

The development of a sustainable and environmentally friendly energy economy encompasses efficient hydrogen production from renewable energy via electrolysis. In this context, great efforts have recently been dedicated to the development of more efficient and cost-effective electrocatalysts. Understanding the mechanism of the oxygen evolution reaction (OER) on transition metal oxide catalysts is of great interest, but the reaction and system complexity render the characterization of active sites and the understanding of reaction mechanisms challenging. Time resolved Quick X-ray Absorption Spectroscopy (XAS) can provide dynamic snapshots of the electronic and local structure of nanocatalysts, revealing the 'real active phase' of the catalyst, which can substantially differ from the as-prepared catalyst powder or the catalyst in form of an electrode under non-operating conditions. In this contribution, several examples will be presented showing how operando XAS can reveal catalyst-support interactions, changes in the reaction mechanism, and dynamic reversible/irreversible changes in the electronic and local structure of OER catalysts.

Establishing the Link across the Synthesis Reaction Kinetics, Structural Changes, and Photocatalytic Efficiency of an Enhanced Chitosan–Clay (1:3) Nanocomposite

This research investigates the influence of synthesis kinetics on the structural and photocatalytic properties of chitosan–clay nanocomposites (Cs/MMT) and chitosan–hectorite nanocomposites (Cs/HET), employing an optimized initial stoichiometry of 1:3. Utilizing a variety of analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR), the study explores the structural evolution of the nanocomposites and their photocatalytic performance using semiconductor catalysts TiO2 and ZnO. The findings emphasize the significant impact of reaction kinetics, particularly after 3 h of reaction time, on the structural features of the nanocomposites. Notably, Cs/MMT demonstrates greater crystalline stability compared to Cs/HET due to variations in octahedral cavity occupancy in the initial clays. FTIR and TEM analyses depict the progressive evolution of the nanocomposites during the reaction, shedding light on how reaction kinetics drive the formation of specific bonds within the nanocomposites. In terms of photocatalytic activity, this study provides insights into the complex dynamics of photocatalytic degradation, with a specific focus on the performance of TiO2 and ZnO under diverse experimental conditions. The superior efficacy of TiO2 as a catalyst, particularly when integrated with Cs/MMT nanocomposites, is unequivocally demonstrated, with degradation rates exceeding 80%. This preference stems from TiO2 consistently exhibiting higher degradation rates compared to ZnO, attributed to structural disparities between montmorillonite and hectorite, influencing catalyst–support interactions. The findings underscore the critical importance of selecting suitable catalyst and support matrix combinations for optimizing performance in specific applications.

Recent Advances on Computational Modeling of Supported Single-Atom and Cluster Catalysts: Characterization, Catalyst–Support Interaction, and Active Site Heterogeneity

To satisfy the need for catalyst materials with high activity, selectivity, and stability for energy conversion, material design and discovery guided by theoretical insights are a necessity. In the past decades, the rise in theoretical investigations into the properties of catalyst materials, reaction mechanisms, and catalyst design principles has shed light on the catalysis field. Quantitative structure–activity relationships have been developed through incorporating spectroscopic simulations, electronic structure calculations, and reaction mechanistic studies. In this review, we report the state-of-the-art computational approaches to catalyst materials characterization for supported single-atom and cluster catalysts utilizing spectroscopic simulations, i.e., XANES simulation, and material properties investigation via electronic-structure calculations. Furthermore, approaches regarding reaction mechanisms, focusing on active site heterogeneity, are also discussed.

Efficient Co0.85Se-CNT sulfur cathode derived from strong catalyst-support interactions: Contribution of adsorption-catalysis mechanism to the redox kinetics of polysulfides

The sluggish conversion chemistry and the notorious ‘shuttle effect’ of lithium polysulfides (LiPSs) are hindering the widespread application of lithium-sulfur batteries (LSBs). Herein, N-doped carbon nanotubes arrays anchored with highly dispersed Co0.85Se nanoparticles were in-situ grown on 3D carbon paper substrates (Co0.85Se-CNT@CP) to promote redox kinetic. The derived sulfur cathode (S/Co0.85Se-CNT@CP) exhibited a sufficient chemisorption ability to accelerate the conversion kinetics and showed considerable capability (1210 mAh/g at 0.2C) and impressive cyclic stability (516 mAh/g at 2.0C after 500cycles). Even at a high loading of 6.0 mg cm−2, the assembled batteries performed a high capacity of 500 mAh/g at 2.0C after 500cycles. The exceptional performance is attributed to the following reasons: On the one hand, the highly efficient conductive carbon nanotubes not only offer sufficient accommodation space for sulfur, but also provide physically confinement for polysulfides. On the other hand, the Co0.85Se nanoclusters drove the transformation of more elemental sulfur to Li2S2/Li2S. In addition, the S/Co0.85Se-CNT@CP did not require conventional binders, thus enhanced surface the reaction kinetic and electron transfer. The associated conversion mechanism was studied by ex-situ XPS, and an adsorption-catalytic model was established to elucidate the electrochemical mechanism. This study proposes a feasible strategy to solve the severe LiPSs shuttling and the sluggish conversion kinetics of LSBs.

Enhancing Polymer Electrolyte Membrane Fuel Cells with Ionic Liquids: A Review.

Polymer electrolyte membrane fuel cells (PEMFCs) represent a promising clean energy solution. However, their widespread adoption faces hurdles related to component optimization. This review explores the pivotal role of ionic liquids (ILs) in enhancing PEMFC performance, focusing on their role in polymer electrolyte membranes, catalyst modification, and other components. By addressing key obstacles, including proton conductivity, catalyst stability, and fuel crossover, ILs provide a pathway towards the widespread commercialization of PEMFCs. In the realm of PEMFC membranes, ILs have shown great potential in improving proton conductivity, mechanical strength, and thermal stability. Additionally, the utilization of ILs as catalyst modifiers has shown promise in enhancing the electrocatalytic activity of electrodes by serving as an effective stabilizer to promote the dispersion of metal nanoparticles, and reduce their agglomeration, thereby augmenting catalytic performance. Furthermore, ILs can be tailored to optimize the catalyst-support interaction, ultimately enhancing the overall fuel cell efficiency. Their unique properties, such as high oxygen solubility and low volatility, offer advantages in terms of reducing mass transport and water management issues. This review not only underscores the promising advancements achieved thus far but also outlines the challenges that must be addressed to unlock the full potential of ILs in PEMFC technology, offering a valuable resource for researchers and engineers working toward the realization of efficient and durable PEMFCs.

High-entropy PtCuSnWNb nanoalloys as efficient and stable catalysts for ethanol oxidation electrocatalysis.

Ternary nanoalloys used as electrochemical ethanol oxidation catalysts for direct ethanol fuel cells are confronted with poor stability issues under harsh acidic operating conditions. To address this issue, a carbon-supported quinary PtCuSnWNb high-entropy nanoalloy (denoted as PtCuSnWNb/C) was synthesized by using a polyol reduction method. Due to the unique high-entropy mixing states and strong catalyst-support interactions, PtCuSnWNb/C shows robust structural and compositional stability.

Strong Catalyst-Support Interaction in WOx Nanowires Supported Iridium Nanocatalysts: A Pathway to Efficient Water Electrolysis

This paper investigates the use of sub-stoichiometric tungsten oxide nanowires (WOxNW) as a support material for Ir nanocatalysts in the oxygen evolution reaction (OER) for proton exchange membrane water electrolysis (PEMWE). The results demonstrate that Ir@WOxNW has exceptional activity and durability, which paves the way for large-scale PEMWE deployment. The catalyst-support interaction plays a crucial role in explaining this performance boost.The preparation and characterization of Ir@WOxNW involved loading ultra-fine Ir nanoparticles onto WOxNW through hydrothermal treatment. High-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the iridium nanoparticles were uniformly loaded on the WOxNW support material, indicating efficient loading and dispersion. X-ray photoelectron spectroscopy (XPS) analysis showed that the supported Ir catalysts had a mixed valence state of Ir0 and Ir4+. Ir@WOxNW was compared with three other Ir-based OER catalysts, outperforming them in terms of activity and durability.The Ir@WOxNW catalyst demonstrated superior OER activity compared to the other three catalysts, with a mass activity of 812 A/gIr at 1.55 V vs reversible hydrogen electrode (RHE). The Tafel slopes of the OER catalysts were grouped into two categories: Ir Black and Ir@WOxNW showed smaller values (about 40 mV/dec), and larger values for Ir@ATO and Ir Oxide (about 120 mV/dec), respectively. Electrochemical impedance spectroscopy (EIS) measurements indicated that the high mass activity of Ir@WOxNW was due to a high population of catalytic sites with fast intrinsic kinetics from the dispersed ultra-fine Ir catalyst on WOxNW. The durability of all catalysts was investigated using an accelerated durability test (ADT), and the Ir@WOxNW catalyst demonstrated unexpectedly high durability compared to the other catalysts.The postmortem XPS analysis showed that the Ir@WOxNW catalyst exhibited a subtle change in Ir0/Ir4+ ratio after the ADT, indicating suppressed Ir oxidation and greater stability compared to the other catalysts. Additionally, non-destructive depth profile analysis by synchrotron based XPS was conducted on the supported ultrafine Ir catalysts before and after the ADT test. The difference in oxidation state increased as the supported Ir catalysts were probed deeper into the core. The results showed that after oxidation potential cycles ADT, the WOxNW-supported Iridium exhibited strong resistance to oxidation. The core location remained a high percentage of metal peak, in contrast to the other three control catalysts.Density functional theory calculations suggested that the oxygen-deficient WOxNW support helps to maintain the OER-active metal@metal oxide core@shell-like form of the Ir catalyst particles by enhancing electron transfer from the WOxNW to the Ir surface, thereby weakening the binding of oxygen to the Ir surface and enhancing the oxidation resistance of the Ir metal to oxides.In conclusion, ultrafine Ir nanoparticles supported on WOxNW have significant potential for practical applications in electrochemical water splitting. The high activity and durability of Ir@WOxNW make it a promising candidate for large-scale PEMWE deployment.

TiNxOy/TiN Supported Ir-Oxide/Ir As Efficient OER Electrocatalyst for Acidic Water Electrolysis

Increasing the mass activity of Iridium-based electrocatalysts for oxygen evolution reaction (OER) is of significant importance for sustainable acidic water electrolyzers generating green hydrogen. Here, we have studied surface oxidized TiN (TiNxOy/TiN) as a catalyst support for Ir-based OER electrocatalysts with high mass activity. TiNxOy/TiN supported Ir-oxide/Ir nanoparticles were synthesized using a microwave-assisted approach. The synthesized IrO2@Ir/TiN with an Ir loading of 40 wt% exhibits a mass-normalized OER activity of ~2.4 times that of a commercial benchmark IrO2 OER electrocatalyst. The synthesized TiNxOy/TiN supported Ir-oxide/Ir catalyst, owing to superior utilization of the active catalyst surface and improved intrinsic activity through catalyst-support interaction, enables significant (~60 wt.%) reduction in the Ir metal loading required to obtain equivalent OER performance, compared to commercial benchmark. In addition, accelerated stress test (AST) involving potential cycling in acidic media suggest the IrO2@Ir/TiN catalyst to be of relatively higher durability (activity retention: 79%) compared to that of the commercial equivalent (activity retention: 66%). In the presentation, we discuss the findings focusing on impacts of surface chemistry of the synthesized catalysts on their mass-activity and the degradation mechanisms during AST. The study opens a new perspective for further research towards development of low-Ir loading OER electrocatalysts. Reference Karade, S. S.; Sharma, R.; Gyergyek, S.; Morgen, P.; Andersen, S. M., ChemCatChem 2023, e202201470, DOI: https://doi.org/10.1002/cctc.202201470.