Properties Of Electrocatalysts Research Articles

Unassisted photoelectrochemical CO2 reduction by employing III–V photoelectrode with 15% solar‐to‐fuel efficiency

AbstractSolar‐driven carbon dioxide reduction reaction (CO2RR) provides an opportunity to produce value‐added chemical feedstocks and fuels. However, achieving efficient and stable photoelectrochemical (PEC) CO2RR into selective products is challenging owing to the difficulties associated with the optical and the electrical configuration of PEC devices and electrocatalyst properties. Herein, we construct an efficient, concentrated sunlight‐driven CO2RR setup consisting of InGaP/GaAs/Ge triple‐junction cell as a photoanode and oxide‐derived Au (Ox‐Au) as a cathode to perform the unassisted PEC CO2RR. Under one‐sun illumination, a maximum operating current density of 11.5 mA cm–2 with an impressive Faradaic efficiency (FE) of ~98% is achieved for carbon monoxide (CO) production, leading to a solar‐to‐fuel conversion efficiency of ~15%. Under concentrated intensity of 10 sun, the photoanode records a maximum current density of ~124 mA cm–2 and maintains ~60% of FE for CO production. The results demonstrate crucial advancements in using III–V based photoanodes for concentrated PEC CO2RR.

Development of NiFeSx for Selective Oxygen Evolution Reaction (OER) in Alkaline Seawater: Mitigating Chlorine Evolution in Next-Gen Seawater Electrolysis Devices

Efficient seawater electrolysis for hydrogen production faces challenges like active site poisoning, chloride oxidation, and anode corrosion, necessitating the development of effective oxygen evolution reaction (OER) electrocatalysts[1]. Strategies such as enhancing OER kinetics, mitigating chloride oxidation, bolstering corrosion resistance, and integrating multifunctionality into electrocatalysts are being pursued. Researchers explore internal and external cultivation methods to optimize electrocatalyst properties while understanding structural evolution and OER mechanisms remains crucial. Seawater electrolysis, tapping into Earth's abundant seawater resources, offers a scalable solution for green hydrogen production, especially when paired with renewable energy sources[2]. It holds promise for providing energy and water to offshore areas and mobile maritime systems, crucial for addressing energy and environmental challenges. In this study, we have fabricated a PGM (platinum group metal) free anode that shows promising performance in alkaline seawater. The material consists of nanoclusters of FeNiSx.This study applied a polyol-assisted hydrothermal synthesis strategy to describe an advanced procedure for synthesising NiFeSx. Several physical and chemical characterisation tools are applied to investigate the anode electrode for alkaline seawater oxidation XRD, SEM, TEM and electrochemical characterisation. The outcomes of these characterisations were displayed as graphs. The catalysts reveal nanocluster morphologies. The figure below depicts the preliminary findings, illustrating the electrochemical performance and the physical characterisations. Figure 1 (a) and (b) depict the morphological evaluation by electron microscopy revealing the nanostructure-based clusters of the produced materials with the scanning and transmission electron microscopy, respectively. In. Polarisation curves of the oxygen evolution activity of the synthesised NiFeiSx electrocatalysts on Ni foam working electrodes, in a three-electrode configuration with Pt wire serving as the counter and Hg/HgO serving as the reference electrode in 0.1M KOH + 0.5 NaCl electrolyte. The best-performing catalysts obtained a high current exchange density close to 225 mAcm-2 shown in Figure 1(c). In addition, we are evaluating the efficacy of this high-performance anode electrocatalyst in a single-cell electrolyser and the best and most stable catalyst will be tested in stacks we are developing with our partners in the ANEMEL project.Our research methodology encompasses a comprehensive array of ex-situ and in-situ characterization techniques to delve into the intricacies of seawater electrolysis for hydrogen production. We will utilize impedance spectroscopy to dissect electrochemical behaviour, including resistance, capacitance, and charge transfer resistance. Additionally, chronopotentiometry/chronoamperometry will assess the catalyst's long-term stability, while real-time examination of catalyst crystal structure during OER will be facilitated by Powder X-ray diffraction (XRD). Surface chemistry and elemental composition analysis will be conducted using X-ray photoelectron spectroscopy (XPS), while in-situ Raman spectroscopy will offer insights into electronic structure changes during the reaction, shedding light on the OER mechanism. Furthermore, FTIR spectroscopy will unveil reaction intermediates and mechanisms, providing a detailed understanding of the reaction pathway. Post-mortem catalyst analysis post-electrochemical testing will evaluate degradation, ultimately aiding in optimizing catalyst design for long-term stability and high-performance OER. Acknowledgements The authors acknowledge the ANEMEL Project funded by the Horizon Europe (European Innovation Council) Grant agreement 101071111. Figure 1

Green synthesis of perovskite-type FeMnO3 nanoparticles: Study of its electrochemical hydrogen storage and catalytic activity on the thermal decomposition of ammonium perchlorate

Perovskite-based mixed metal oxides have become a promising material as efficient catalysts and electrocatalysts for various energy storage-related and fuel applications in modern scientific society. This study is the first attempt to explore the catalyst and electrocatalyst application of iron manganese oxide (FeMnO3) perovskite. The pure FeMnO3 nanoparticles (NPs) were synthesized using a green method by Aloe vera extract as a capping agent. The cubic crystal structure, nanosized particle, purity, mesoporous feature and ferromagnetic properties of FeMnO3 NPs were confirmed using XRD, FT-IR, FESEM-EDS mapping, BET, and VSM analysis. The electrocatalyst properties of the sample were measured using cyclic voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the specific capacitance value and hydrogen storage capacity of FeMnO3 NPs were about 382.5 Fg−1 and 2622 mAhg−1 in the aqueous alkaline medium (3 M KOH), respectively. Additionally, the catalytic activity of the sample on the thermal decomposition of ammonium perchlorate (AP) was analyzed using differential scanning calorimetry (DSC) and thermogravimetry (TGA) instruments. The results revealed that FeMnO3 NPs enhanced the released heat of AP from 525 to 1760 Jg−1 and reduced the decomposition temperature from 458 to 381 °C.

Nickel-based hydroxide composite as electrocatalyst for hydrogen evolution reaction

The development of earth-abundant transition-metal-based electrocatalysts for hydrogen evolution reaction (HER) is commercial. In this work, Fe (Co) and Ni hydroxide nanocomposites on Ni foam were synthesized as HER catalyst, FeNi-LDH/NF has the overpotentials of 291 mV at 50 mA cm−2 and 369 mV at 100 mA cm−2. It is found that FeNi-LDH/NF and CoNi-LDH/NF have large Cdl and ECSA, low Rct. Therefore, this simple method to prepare FeNi-LDH/NF and CoNi-LDH/NF can enhance the properties of electrocatalysts, which make FeNi-LDH/NF and CoNi-LDH/NF a promising material to replace noble metal-based catalysts.

Origin of Stability and Activity Enhancements in Pt-Based Oxygen Reduction Reaction Catalysts Via Defect-Mediated Dopant Adsorption

Platinum alloys are highly efficient electrocatalysts for the oxygen reduction reaction (ORR) in acidic conditions. However, these alloys are susceptible to metal loss through leaching and degradation, leading to reduced catalyst stability and activity. Recently, it has been shown that doping with oxophilic elements can significantly alleviate these problems, with a prominent example being Mo-doped Pt alloys. Here, to achieve atomic scale understanding of the exceptional activity and stability of these alloys, we present a detailed density functional theory description of the dopants’ structures and impact on electrocatalyst properties. Beginning with the Mo/Pt system, we demonstrate that Mo can be stabilized in the form of low-dimensional oxyhydroxide moieties on Pt defects. The resulting structures enhance stability and activity via distinct physical processes, with the Mo moieties both directly inhibiting Pt dissolution at defects and indirectly enhancing ORR activity by generation of strain fields on surrounding Pt terraces. We then generalize these analyses to other metal dopant elements, and we demonstrate that similar low-dimensional oxyhydroxide structures control the electrocatalytic properties through an intricate interplay of the structures’ acid stability, intrinsic activity for the ORR, and ability to induce ORR-promoting strain fields on Pt.Reference:Sawant, K., Zeng, Z. & Greeley, J., Angew. Chem., Int. Ed., 10.1002/anie.202312747

Operando X-Ray Scattering for Electrocatalysis and Beyond

The energy transition stands as one of the greatest challenges of today’s society. In this context, electrocatalyst materials at the heart of electrochemical energy conversion devices such as fuel cells and water electrolyzers are expected to play an increasing crucial role in the near future. The urgent bottleneck to be overcome in electrocatalyst materials development to allow the widespread deployment of electrochemical systems is thus reaching combined high activity and long-term stability at low cost. Despite the diversity in electrocatalyst materials, the latter being largely imposed by the various types of electrochemical systems (noble vs. non-noble metals in acidic vs. alkaline media for example) and the prerequisites of the different electrochemical processes (oxidation or reduction reactions of various species at different electrode potential ranges), most activity and stability properties of electrocatalysts directly derive from their (surface) chemistry and structure [1]. Such properties (and their temporal evolution) can thus be directly investigated by means of in situ or operando high energy X-ray scattering (XRD) technique [2].In this presentation, the versatility of in situ and operando XRD technique in addressing key bottlenecks in electrocatalyst materials development, notably by probing adsorption and oxidation trends [3], will be showcased. After an overview of previous contributions from the literature, the talk will focus on our ongoing works which encompass the study of Pt-based nanocatalysts for the oxygen reduction reaction (ORR) at proton-exchange membrane fuel cells (PEMFCs) anode, carbon-capped Ni@C catalyst for the hydrogen oxidation reaction (HOR) at anion-exchange membrane fuel cells (AEMFCs) anode and IrCu unsupported aerogel catalyst for the oxygen evolution reaction (OER) at proton-exchange membrane water electrolyzers (PEMWEs) anode.Finally, the ability of operando XRD to provide device-relevant insights at the macroscale (such as ionomer hydration in PEMFCs or water distribution in AEMFCs) beyond electrocatalysts microstructural properties will be presented.

Ultrathin high-entropy layered double hydroxide electrocatalysts for enhancing oxygen evolution reaction

At the heart of the oxygen evolution reaction (OER), the properties of electrocatalysts play a crucial role in determining reaction efficiency. This underscores the need to design and develop highly effective OER electrocatalysts. The unique layer structure and electronic properties make layer double hydroxide (LDH) a promising candidate for driving OER electrocatalysis. Furthermore, high-entropy materials (HEMs) exhibit core effects such as high entropy, lattice distortion, sluggish diffusion, and cocktail effect, which can enhance active sites and optimize binding energy with intermediates. Combining the advantages of these two material categories, we propose the synthesis of high-entropy layered double hydroxides (HE-LDHs) through a straightforward MOF-mediated synthesis method to showcase exceptional electrocatalytic OER performance. Detailed mechanistic studies have shown that its outstanding performance stems from its ultrathin structure and the inherent activity of a high-entropy material that promotes charge transfer, mass transport, and the evolution of reaction intermediates.

Synthesis and Catalytic Performance of Bimetallic Oxide-Derived CuO-ZnO Electrocatalysts for CO2 Reduction.

Steering the selectivity of electrocatalysts toward the desired product is crucial in the electrochemical reduction of CO2. A promising approach is the electronic modification of the catalyst's active phase. In this work, we report on the electronic modification effects on CuO-ZnO-derived electrocatalysts synthesized via hydrothermal synthesis. Although the synthesis method yields spatially separated ZnO nanorods and distinct CuO particles, strong restructuring and intimate atomic mixing occur under the reaction conditions. This leads to interactions that have a profound effect on the catalytic performance. Specifically, all of the bimetallic electrodes outperformed the monometallic ones (ZnO and CuO) in terms of activity for CO production. Surprisingly, on the other hand, the presence of ZnO suppresses the formation of ethylene on Cu, while the presence of Cu improves CO production of ZnO. In situ X-ray absorption spectroscopy studies revealed that this catalytic effect is due to enhanced reducibility of ZnO by Cu and stabilization of cationic Cu species by the intimate contact with partially reduced ZnO. This suppresses ethylene formation while favoring the production of H2 and CO on Cu. These results show that using mixed metal oxides with different reducibilities is a promising approach to alter the electronic properties of electrocatalysts (via stabilization of cationic species), thereby tuning the electrocatalytic CO2 reduction reaction performance.

Emerging MXene-based electrocatalysts for efficient nitrate reduction to ammonia: recent advance, challenges, and prospects

Ammonia (NH3) plays an irreplaceable role in traditional agriculture and emerging renewable energy. Its preparation in industry mainly relies on the energy-intensive Haber-Bosch process, which is associated with high energy consumption and large CO2 emissions. Recently, the nitrate reduction reaction (NO3-RR) driven by renewable energy has received extensive attention. This reaction can efficiently synthesize NH3 with water as a hydrogen source and NO3- as a nitrogen source under mild conditions, which is conducive to reducing energy consumption and promoting the carbon cycle. It is well known that the properties of electrocatalysts determine the performance of NO3-RR. As an emerging two-dimensional material, MXenes (transition metal carbides/nitrides/carbon nitrides) possess excellent electrical conductivity, large specific surface area and controllable surface functional groups, which shows great application potential in the field of NO3-RR. Herein, this review summarized the structure, properties and synthesis strategies of MXenes to elucidate the possibilities from foundation to application. Then, the latest research progress in applying MXene-based electrocatalysts to NO3-RR was summarized and the applicability of different NH3 detection methods was analyzed. Finally, the present challenges and future prospects of NO3-RR were presented. This review aimed to provide thoughtful insights into the rational design of MXene-based electrocatalysts for sustainable NH3 synthesis.

What Limits Conquest of Stability Descriptors? – Intriguing Aspects of Dissolution of Oxygen Evolution Electrocatalysts

AbstractDesign of active and stable electrocatalysts for the oxygen evolution reaction (OER) requires in‐depth understanding of the electrocatalyst properties and interfacial structural dynamics during OER. One of the essential insights for advanced electrocatalyst design is vivid understanding of the drivers and mechanisms of dissolution of electrocatalysts. In this work we analyze some important aspects of electrocatalyst dissolution during OER, to deepen and advance our understanding of activity‐stability relations and relevant stability descriptors.

Morphology engineering of self-assembled bimetallic PtCo alloy nanofoams as efficient multifunctional electrocatalysts for oxygen reduction and alcohol oxidation

The exploration of high properties of electrocatalysts is imperative for the commercialization application of fuel cells. Enhancing the catalytic activity and stability of Pt-based catalysts can be achieved by rationally designing their morphology and composition. Here, we synthesized self-assembled PtCo alloy nanofoams (ANs) catalysts with controllable surface composition and porous network. The experimental results show that prepared PtxCo1-ANs catalysts display excellent electrochemical performance in oxygen reduction reaction (ORR), methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Interestingly, the mass activities of Pt2Co1-ANs with optimized surface composition for ORR, MOR, and EOR are 6.41, 6.64, and 7.71-fold higher than commercial Pt/C catalysts, respectively. Meantime, it also maintains high electrocatalytic durability in ORR, MOR, and EOR. Such results ascribe to the modified surface composition, optimized electronic structure, and porous interconnected nanofoam structure. These findings provide valuable insights into the design of highly active and durable multifunctional electrocatalysts with controllable shapes and composition.

Ultrathin graphitic carbon nitride interface layer regulated nickel-iron oxyhydroxide stabilized on nickel foam for efficient oxygen evolution reaction

Regulating interfacial properties of electrocatalysts to enhance the performance of oxygen evolution reaction (OER) possesses practical significance for water splitting. Herein, we report a novel strategy to form a graphitic carbon nitride (g-C3N4) interface layer on nickel foam (NF), followed by the growth of nickel-iron (oxy)hydroxides (NiFe-OH). The NiFe-OH nanosheets are tightly anchored on the g-C3N4 layer, exhibiting enhanced surface and structural characteristics. Therefore, the as-prepared NF/g-C3N4/NiFe-OH demonstrates superior OER activity with low overpotentials of 272, 342, and 476 mV at the current densities of 50, 100, and 200 mA cm−2, respectively. The reduced Tafel slope and raised TOF values of the electrode compared to NF/NiFe-OH reveal the promoting roles of g-C3N4, which provides more active sites, induces charge redistribution, and facilitates electron transfer. Furthermore, the electrode presents reliable stability and durability without observable morphological damage, alteration in the surface chemical state, and significant depletion of active components.

Application of Amorphous-Crystalline Coupling Materials in Electrocatalysis.

Interface engineering has proven to be a highly efficient strategy for modulating the physicochemical properties of electrocatalysts and further enhancing their electrochemical performance in related energy applications. In this context, the newly proposed crystalline-amorphous (c-a) heterostructures with unusual atomic arrangements at interfaces show strong competitiveness. Nonetheless, few efforts have been made to reveal and summarize the structure-activity relationship at the two-phase interface and the corresponding electrocatalytic mechanism. This concept is devoted to comprehensively discussing the fundamental characteristics of crystalline-amorphous electrocatalysts and their application in the field of energy conversion with typical examples. In addition, the development prospects and opportunities of crystalline-amorphous heterostructure are summarized to provide potential development directions for other types of clean energy development.

A review of carbon-based catalysts and catalyst supports for simultaneous organic electro-oxidation and hydrogen evolution reactions

Producing organic electro-oxidation and hydrogen evolution reactions (HER) simultaneously in an electrolytic cell is an appealing method for generating valuable chemicals at the anode while also producing H2 at the cathode. Within this framework, the task of designing energy-saving electrocatalysts with high selectivity and stability is a considerable challenge. Carbon-based catalysts, along with their supports, have emerged as promising candidates due to their diverse sources, large specific surface area, high porosity and multidimensional characteristics. This review summarizes progress from 2012 to 2022, in the use of carbon-based catalysts and their supports for organic electrooxidation and HER. It delves into outer-sphere electrooxidation mechanisms involving molecule-mediated oxidation and oxidative radical coupling reactions, as well as inner-sphere electrooxidation mechanisms, encompassing both acidic and alkaline electrolytes. The review also explores prospective research directions within this domain, addressing various aspects such as the design of electrocatalytic materials, the study of the relationship between the structure and properties of electrocatalysts, as well as examining their potential industrial applications.

Transforming Nature's Bath Sponge into Stacking Faults-Enhanced Ag Nanorings-Decorated Catalyst for Hydrogen Evolution Reaction.

The rational design of cost-effective and efficient electrocatalysts for electrochemical water splitting is essential for green hydrogen production. Utilizing nanocatalysts with abundant active sites, high surface area, and deliberate stacking faults is a promising approach for enhancing catalytic efficiency. In this study, we report a simple strategy to synthesize a highly efficient electrocatalyst for the hydrogen evolution reaction (HER) using carbonized luffa cylindrica as a conductive N-doped carbon skeleton decorated with Ag nanorings that are activated by introducing stacking faults. The introduction of stacking faults and the resulting tensile strain into the Ag nanorings results in a significant decrease in the HER overpotential, enabling the use of Ag as an efficient HER electrocatalyst. Our findings demonstrate that manipulating the crystal properties of electrocatalysts, even for materials with intrinsically poor catalytic activity such as Ag, can result in highly efficient catalysts. Further, applying a conductive carbon backbone can lower the quantities of metal needed without compromising the HER activity. This approach opens up new avenues for designing high-performance electrocatalysts with very low metallic content, which could significantly impact the development of sustainable and cost-effective electrochemical water-splitting systems.

Exploring suitability of solid 3D substrates for designing self-supported electrocatalysts for water splitting.

The choice of solid 3D substrates to design electrocatalysts significantly impacts the efficiency and effectiveness of self-supported electrocatalysts used in water splitting. These substrates are pivotal in significantly boosting the performance by providing structural support, facilitating electron transport, and increasing the active surface area. This improvement leads to higher catalytic performance and better stability, ultimately optimizing the electrocatalytic process. The interaction between the substrate and the electrocatalyst can also affect the intrinsic properties of the catalyst, further influencing its performance. Therefore, understanding and optimizing the use of solid 3D substrates is vital for advancing water-splitting technologies. This article explores the critical role of solid 3D substrates in enhancing the activity of self-supported materials for water splitting. By examining recent developments and research in this region, we target to showcase a comprehensive understanding of how different 3D substrates influence electrocatalyst properties and performance and to highlight future directions for optimizing these systems in water-splitting applications.

Origin of Stability and Activity Enhancements in Pt-based Oxygen Reduction Reaction Catalysts via Defect-Mediated Dopant Adsorption.

Platinum alloys are highly efficient electrocatalysts for the oxygen reduction reaction (ORR) in acidic conditions. However, these alloys are susceptible to metal loss through leaching and degradation, leading to reduced catalyst stability and activity. Recently, it has been shown that doping with oxophilic elements can significantly alleviate these problems, with a prominent example being Mo-doped Pt alloys. Here, to achieve atomic scale understanding of the exceptional activity and stability of these alloys, we present a detailed density functional theory description of the dopants' structures and impact on electrocatalyst properties. Beginning with the Mo/Pt system, we demonstrate that Mo can be stabilized in the form of low-dimensional oxyhydroxide moieties on Pt defects. The resulting structures enhance stability and activity via distinct physical processes, with the Mo moieties both directly inhibiting Pt dissolution at defects and indirectly enhancing ORR activity by generation of strain fields on surrounding Pt terraces. We then generalize these analyses to other metal dopant elements, and we demonstrate that similar low-dimensional oxyhydroxide structures control the electrocatalytic properties through an intricate interplay of the structures' acid stability, intrinsic activity for the ORR, and ability to induce ORR-promoting strain fields on Pt.

Origin of Stability and Activity Enhancements in Pt‐based Oxygen Reduction Reaction Catalysts via Defect‐Mediated Dopant Adsorption

AbstractPlatinum alloys are highly efficient electrocatalysts for the oxygen reduction reaction (ORR) in acidic conditions. However, these alloys are susceptible to metal loss through leaching and degradation, leading to reduced catalyst stability and activity. Recently, it has been shown that doping with oxophilic elements can significantly alleviate these problems, with a prominent example being Mo‐doped Pt alloys. Here, to achieve atomic scale understanding of the exceptional activity and stability of these alloys, we present a detailed density functional theory description of the dopants’ structures and impact on electrocatalyst properties. Beginning with the Mo/Pt system, we demonstrate that Mo can be stabilized in the form of low‐dimensional oxyhydroxide moieties on Pt defects. The resulting structures enhance stability and activity via distinct physical processes, with the Mo moieties both directly inhibiting Pt dissolution at defects and indirectly enhancing ORR activity by generation of strain fields on surrounding Pt terraces. We then generalize these analyses to other metal dopant elements, and we demonstrate that similar low‐dimensional oxyhydroxide structures control the electrocatalytic properties through an intricate interplay of the structures’ acid stability, intrinsic activity for the ORR, and ability to induce ORR‐promoting strain fields on Pt.

Elucidation of the Interplay between the Features of the Precursor and the Physicochemical Properties of “Core-Shell” Hierarchical Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a major bottleneck in the operation of proton-exchange membrane fuel cells (PEMFCs) since it introduces large overpotentials (no less than 250-300 mV), which degrade significantly the energy conversion efficiency of the device. In addition, the electrocatalysts (ECs) yielding the lowest ORR overpotentials in the acidic environment found at the PEMFC cathode are based on Pt, a very scarce critical raw material (CRM). Pt raises concerns as it might trigger serious supply bottlenecks in the event of a practical widespread implementation of PEMFCs in the framework of today’s energy transition. Hence, the development of high-performing and durable ECs for the ORR is a major stepping stone towards the large-scale rollout of PEMFCs.In our research group a new breakthrough approach has been devised for the synthesis of ORR ECs, that is completely different form the preparation routes that are commonly adopted in the state of the art [1, 2]. Briefly, the approach consists in the pyrolysis and subsequent treatment of a precursor obtained by coupling suitable carbon species/sacrificial supports with a zeolitic inorganic-organic polymer electrolyte (Z-IOPE). The latter comprises anionic complexes including the Pt “catalyst” and other “co-catalysts”, which are bridged by organic binders [1,2].On one hand, the proposed approach has already shown its potential to yield ECs exhibiting a performance and durability improved with respect to Pt/C benchmark ECs. On the other hand, the proposed approach is extremely flexible, especially with respect to the synthesis of the initial EC precursor. In principle, it is possible to modulate a number of crucial features of such EC precursor, with a particular reference to: (i) the chemical composition (e.g., in terms of Pt, other “co-catalysts” and N; the latter plays a crucial role to stabilize the active sites into “coordination nests” on the EC surface, raising durability); and (ii) the morphology, that can be “templated” on suitable species (e.g., carbon species, sacrificial supports). The very flexibility of the proposed synthetic process needs to be leveraged appropriately to maximize the performance of the final ORR ECs, at the same time minimizing the efforts wasted on approaches with a low development potential.Herein it is elucidated how the modulation in the parameters involved in the synthesis of the EC precursor (e.g., the binder and the approaches to couple the Z-IOPE with the support) impact the physicochemical and electrochemical properties of the final ECs, with a particular reference to the chemical composition, morphology and distribution of the ORR active sites. An extensive characterization of the final ECs is carried out. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are adopted to determine the bulk chemical composition. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to elucidate the surface chemical composition and the chemical states of the surface elements. Ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM) allow for the elucidation of EC morphology. The porosimetric features are probed by automatic gas adsorption instrumentations. Wide-angle X-ray diffraction (WAXD) is crucial to resolve the crystal structure. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) is used to clarify the “ex-situ” electrochemical performance and ORR reaction mechanism. Finally, the most promising ECs are used in the fabrication of single PEMFCs, that are tested as a function of the operating conditions.It is revealed that, in comparison with the Pt/C benchamark, some ECs are characterized by a much higher intrinsic kinetic performance due to the electronic and bifunctional effects bestowed by the carbon nitride support and the «co-catalysts». Finally, the binder has a marked effect on the stoichiometry, size, and distribution of the PtMx aggregates bearing the active sites.

Development of a Robust Electrochemical Ammonia Electrolysis Protocol Using in Operando Quantitative Analysis

Ammonia electrolysis is an eco-friendly technology that shows promise for producing clean hydrogen. Compared to water electrolysis, ammonia electrolysis only requires a low external voltage of 0.06 V to produce hydrogen. This research proposes a simple protocol for evaluating the practical properties of electrocatalysts for ammonia electrolysis using in-operando gas chromatography. The protocol allows for reliable and efficient comparison and evaluation of new ammonia oxidation catalysts, including distinguishing between competitive oxidation reactions and monitoring them in real-time. Additionally, the author investigated the correlation between physical or electrochemical surface areas and stability performances to estimate practical stability based on half-cell analysis. The use of this rigorous protocol should aid in evaluating the practical performance of ammonia oxidation and contribute to identifying viable pathways for the practical electrochemical oxidation of ammonia to hydrogen.