Nanocatalysts For Oxygen Reduction Reaction Research Articles

The Synthesis of Highly Durable Pt-Based Hollow Nanocatalysts for Oxygen Reduction Reaction

Platinum (Pt) catalysts have been considered as the most active electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells. However, cost and durability of Pt catalysts are the biggest obstacles impeding their practical applications. In this talk, the combination of Pt ion-treatment and acid-treatment methods is developed to prepare Pt-based hollow nanocatalysts. Catalytic results indicated the ORR performance of our Pt-Ni nanocatalysts far exceed that of commercial Pt/C electrocatalysts, in terms of mass-specific activities it is up to a 19-fold increase than that of Pt/C and 6 times than that of Department of Energy requirement (0.44 A/mg Pt). The performance loss of Pt-Ni is negligible even after a prolonged durability test of 300,000 cycles. The in-situ spectroelectrochemical results and theoretical simulation further explain the catalytic mechanism and such excellent durability. We believe our method provides an effective strategy for the rational design of Pt-based alloy nanostructures and will help guide the future development of catalysts for their practical applications in energy conversion technologies.

C48, B24N24, CNT(8, 0) and BNNT(8, 0) as catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)

The capacities and performances of Mn doped nanostructures as nano-catalysts for ORR and OER are investigated. The mechanism of ORR by four-electron reaction is opposite of OER and in fuel cell the change in Gibbs free energy of OER is calculated on various surfaces of catalysts. Results shown that the over-potential of ORR on C48, B24N24 and C nanostructures and BN nanostructures are 1.14, 1.10, 1.05 and 0.99 V. Results indicated that the over-potential of OER on C48, B24N24 and C nanostructures and BN nanostructures are 1.10, 1.05, 0.98 and 0.92 V. Results shown that the ΔGreaction of ORR on C48, B24N24 and C nanostructures and BN nanostructures are −0.68, −0.65, −0.57 and −0.52 eV. Results indicated that the ΔGreaction of OER on C48, B24N24 and C nanostructures and BN nanostructures are −0.38, −0.35, −0.29 and −0.27 eV. The Mn-BNNT(8, 0) with high performances is suggested as new catalysts of ORR and OER reactions by theoretical models.

Stable and Efficient Ir Nanoshells for Oxygen Reduction and Evolution Reactions

We report the characterization and applications of core–shell Cu–Ir nanocatalysts for oxygen reduction reaction and oxygen evolution reaction. Core–shell Cu–Ir particles with tunable thickness of Ir can be oxidized to remove the Cu core and obtain Ir shells. The thickness of the Ir shells determines the stability and optimization of the precious metals. We showed with in situ scanning transmission electron microscopy the remarkable stability of the Ir shells at elevated temperatures under oxidative and reductive environments. In situ scanning transmission electron microscopy and in situ X-ray absorption spectroscopy also showed that traces of remaining copper could be detected in the Ir shells. Electrochemical measurements for oxygen reduction and evolution reactions show promising activity and stability compared to a commercial catalyst. Thin Ir shells, with high surface area per gram of Ir, were more active but less stable than thicker shells. In contrast, thicker Ir shells were more stable and had excellent electrochemical properties in aqueous and alkaline environments. Hence, Ir nanoshells appear as interesting candidates for reducing the cost of catalysis while improving chemical performance in fuel cells.

Using an ionomer as a size regulator in γ-radiation induced synthesis of Ag nanocatalysts for oxygen reduction reaction in alkaline solution

Ag nanoparticles (Ag NPs) are among the most promising candidates to replace Pt as the catalyst for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, synthesizing size-controlled Ag NPs with efficient catalytic performance is still challenging. Herein, uniform Ag NPs are produced through a γ-radiation induced synthesis route in aqueous solutions, using the ionomer PTPipQ100 as both an efficient size regulator in the synthesis and a conductor of hydroxide ions during the ORR process. The origin of the size control is mainly attributed to the affinity of the ionomer to metallic silver. The resulting Ag NPs covered with ionomer layers can be applied as model catalysts for ORR. The nanoparticles that were prepared using 320 ppm ionomer in the reaction solution turned out to be coated with a ∼ 1 nm thick ionomer layer and exhibited superior ORR activity as compared to other Ag NPs of similar size studied here. The improved electrocatalytic performance can be attributed to the optimal ionomer coverage that enables fast oxygen diffusion, as well as interactions at the Ag-ionomer interface which promote the desorption of OH intermediates from the Ag surface. This work demonstrates the advantage of using an ionomer as the capping agent to produce efficient ORR catalysts.

Noble-Metal-Free FeMn-N-C catalyst for efficient oxygen reduction reaction in both alkaline and acidic media

The oxygen reduction reaction (ORR) is important cathodic reaction running in several electrochemical energy conversion devices. It is still difficult to develop non-precious nanocatalysts for ORR that have high activity and increased durability for practical application. Herein, bimetallic FeMn(mIm)-N-C composite incorporated with Fe and Mn via an encapsulation-ligand exchange technique is prepared and established as an efficient ORR catalyst. The results reveal that FeMn(mIm)-N-C shows outstanding ORR performance with E1/2 of 0.861 V and 0.778 V in alkaline and acid solutions, along with robust durability. Additionally, the assembled Zn-Air batteries (ZAB) and proton exchange membrane fuel cells (PEMFCs) both have exceptional power densities and show promise for long-term stability compared to 20% Pt/C. The present work provides a useful strategy for designing and synthesizing a reliable low-cost and high-efficient electrocatalysts for energy conversion and storage.

Negatively charged platinum nanoparticles on dititanium oxide electride for ultra-durable electrocatalytic oxygen reduction

Negatively charged Pt nanoparticles supported by a [Ti2O]2+·2e− electride with a self-passivation a-TiOx layer demonstrated superb long-term durability in the electrocatalytic ORR, which is superior to that of commercial Pt/C catalysts.

A Systematic Investigation of Carbon Pretreatment for the Synthesis of Platinum Nano-Catalysts for Oxygen Reduction Reaction

The synthesis of electrocatalysts for low- and high temperature fuel cells is dependent on many different factors that determine the activity of the produced catalysts. One important and highly underrepresented factor in literature are carbon pretreatments, which have a strong impact on the electrochemical activity of the produced catalyst. A web of science search showed that less than 1% of the articles working with the synthesis of Pt-based catalysts for the Oxygen reduction reaction (ORR) contain information on carbon pretreatments. In recent years no articles on the topic of carbon pretreatment for the synthesis of Pt-based ORR catalyst have been published.However, different forms (as powder, nano tubes, etc.) of carbon are commonly used as support material for Pt-based catalysts. Previous work has shown the importance of pretreatment of carbon supports to change the surface-active groups, enhancing the dispersion and reducing agglomeration of Pt-nanoparticles [1]. Oxidizing treatments are known to change the surface groups and decreasing the BET surface area [2]. Furthermore, carbon pretreatments can effectively reduce impurities present in as-purchased carbon [3].A systematic study of pretreatments of Vulcan XC72-R and Ketjen 300 have been carried out followed by the synthesis of supported Pt-nanoparticles using XPS, XRD, TEM, BET and RDE techniques. We found that the presence of sulfur in the surface strongly correlates with the ECSA of the supported Pt catalyst. This talk will elaborate on the effect of pretreatments on the carbon support, the synthesis of Pt nanoparticles and its impact on the resulting electrochemical performance: Compared to as received carbon, the Pt mass activity could be increased by a factor 4, exceeding the mass activity of comparable commercial Pt/C electrocatalysts.[1] Bimetallic Pt–Sn catalysts supported on activated carbon I. The effects of support modification and impregnation strategy - A. Erhan Aksoylu; M. Madalena A. Freitas; Jose L. Figueiredo[2] The effect of pretreatment of Vulcan XC-72R carbon on morphology and electrochemical oxygen reduction kinetics of supported Pd nano-particle in acidic electrolyte - Senthil Kumar, S. M.; Soler Herrero, Jaime; Irusta, Silvia; Scott, Keith[3] Effect of the carbon pre-treatment on the properties and performance for nitrobenzene hydrogenation of Pt/C catalysts - Torres, G. C.; Jablonski, E. L.; Baronetti, G. T.; Castro, A. A.; De Miguel, S. R.; Scelza, O. A.; Blanco, M. D.; Peña Jiménez, M. A.; Fierro, J. L.G. Figure 1

Recent advance on structural design of high-performance Pt-based nanocatalysts for oxygen reduction reaction

Proton exchange membrane fuel cells (PEMFCs) represent a promising technology to overcome the current energy and environmental issues, where high-performance cathodic catalysts are badly needed due to the sluggish kinetics of oxygen reduction reaction (ORR). By far Pt stands for the best ORR catalyst, however, considering the scarcity and high cost, it is imperative to further improve its catalytic activity and atomic efficiency to reduce the loading amount. In view of the key issues, this review concentrates on recent advances on developing high-performance Pt-based nanocatalysts for ORR. The catalytic ORR mechanism was first described, followed by presenting the major principles to regulate ORR activity involving ligand effect and geometric effect. Guided by the principles, typical design strategies of Pt-based nanocatalysts were detailedly summarized, with emphasis on increasing intrinsic activity of single active site and electrochemical active surface area. We finally concluded by providing the remaining challenges and future directions in this field.

Ternary Pdnimo Alloy as Bifunctional Nanocatalysts for Oxygen Reduction Reaction and Hydrogen Revolution Reaction

Ternary Pdnimo Alloy as Bifunctional Nanocatalysts for Oxygen Reduction Reaction and Hydrogen Revolution Reaction

First-principle-data-integrated machine-learning approach for high-throughput searching of ternary electrocatalyst toward oxygen reduction reaction

Platinum (Pt) alloys are expected to overcome long-standing issues of Pt/C electrocatalysts for oxygen reduction reaction (ORR). Entangled with serious uncertainty in configurational and compositional information, the design of a promising multi-component electrocatalyst, however, has been delayed. Here, we demonstrate that a first-principle database-driven machine-learning approach is extremely useful for the purpose via exploring materials beyond the regime of pure quantum mechanical calculations. Guided by a computational ternary phase diagram we indeed experimentally synthesized a PtFeCu nanocatalyst with 2 g per batch capacity and measured its catalytic performance for ORR. Both our computation and experiment consistently demonstrate that PtFeCu is highly active due to the atomic distribution of Cu leading to beneficial modulation of surface strain and segregation. Strikingly, PtFe high Cu low (776 μA cm −2 Pt and 0.67 A mg −1 Pt ) exhibits not only 3-fold better specific and mass activities than Pt/C but also little performance degradation over the accelerated stress test. • First-principle establishment of catalytic property data for ternary nanoparticles • Parametrization of atomistic interaction into neural network potentials • A striking consistency between computational prediction and experimental validation • Exceptional catalytic mass activity of PtFeCu 3-fold higher than that of Pt/C One of the challenging issues in nanocatalyst design for catalysis applications is to introduce the atomic-level functionalities of nanoparticles, determining the activity and stability. Multi-component systems can be promising, but the enormous configurational degrees of freedom and optimization routes for a target reaction remained unsolved. We demonstrate the combination of a machine-learning approach and experimental tests of PtFeCu nanoparticles for oxygen reduction reaction. Promising candidates were efficiently screened theoretically and successfully validated by the experiments. Both our computational and experimental outcomes indicate that the highly active electrocatalytic performance of PtFeCu originates from Cu atomic distribution. Our study suggests that first-principle calculations combined with machine-learning technology can be a promising approach in design of nanocatalysts to reduce the gap between the simulations and experiments. To efficiently design the Pt-based alloy nanocatalysts for oxygen reduction reaction, we utilized first-principle data integrated with machine learning to search for PtFeCu configurational spaces. We identified the promising candidates and revealed the atomic-level understanding via first-principle calculations. Cu atomic distribution remarkably modulated surface strain energies and segregation of the alloying components toward better oxygen reduction reaction performance. Tuning of Cu contents led to the high electrochemical performance of PtFeCu nanocatalysts, which was successfully validated by experiments.

Surface/Near‐Surface Structure of Highly Active and Durable Pt‐Based Catalysts for Oxygen Reduction Reaction: A Review

Proton exchange membrane fuel cells (PEMFCs) are highly promising energy‐conversion devices because of their zero‐emission and high efficiency. A great deal of Pt is of significant necessity on the cathode to accelerate the rate of kinetically sluggish oxygen reduction reaction (ORR) and maintain the long‐term operation, leading to the prohibitive cost of PEMFCs and limiting their widespread deployment. In the past decades, numerous efforts including manipulation of composition, morphology, and structure have been devoted to improving their higher activity and stability, but still lag behind the actual requirement. ORR is a typical surface‐sensitive electrochemical reaction and its process is mainly determined by surface/near‐surface structure. Herein, the recent advances in the manipulation of surface structure are summarized. The ORR mechanism and evaluation method for activity and stability are introduced. Then, solutions toward the engineering of surface structure and its effect on activity and stability are presented. Finally, comments on the future direction of nanocatalysts for ORR are presented in terms of engineered surface structure.

Electrochemical determination of the degree of atomic surface roughness in Pt–Ni alloy nanocatalysts for oxygen reduction reaction

AbstractPt–Ni alloy nanocrystals with Pt‐enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone. The changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area, the potential of zero total charge (PZTC), and relative surface roughness, which were determined from CO‐ and CO2‐displacement experiments before and after 3000 potential cycles under oxygen reduction reaction conditions. While the highest activity and durability were achieved in hydroquinone‐treated Pt–Ni, sulfuric acid‐treated one showed the lower activity and durability despite its higher surface Pt concentration and alloying level. Both PZTC and /Q CO ratio (desorption charge of reductively adsorbed CO2 normalized by COad‐stripping charge) depend on surface roughness. In particular, /Q CO ratio change better reflects the roughness on an atomic scale, and PZTC is also affected by the electronic modification of Pt atoms in surface layers. In this study, a comparative study is presented to find a relationship between surface structure and electrochemical properties, which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt–Ni alloy catalysts with Pt‐rich surfaces.

A Trimetallic Pt2NiCo/C Electrocatalyst with Enhanced Activity and Durability for Oxygen Reduction Reaction

Commercialization of the polymer electrolyte membrane fuel cell (PEMFC) requires that electrocatalysts for oxygen reduction reaction (ORR) satisfy two main considerations: materials must be highly active and show long-term stability in acid medium. Here, we describe the synthesis, physical characterization, and electrochemical evaluation of carbon-dispersed Pt2NiCo nanocatalysts for ORR in acid medium. We synthesized a trimetallic electrocatalyst via chemical route in organic medium and investigated the physical properties of the Pt2NiCo/C nanocatalyst by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy-scanning electron microscope (EDXS-SEM), and scanning transmission electron microscopy (STEM), whereas the catalytic activities of the Pt2NiCo/C and Pt/C nanocatalysts were determined through cyclic voltammetry (CV), CO-stripping, and rotating disk electrode (RDE) electrochemical techniques. XRD and EDXS-SEM results confirmed the presence of the three metals in the nanoparticles, and scanning transmission electron microscopy (STEM) allowed observation of the Pt2NiCo nanoparticles at ~10 nm. The measured specific activity for the synthesized nanocatalyst is ~6.4-fold higher than that of Pt/C alone, and its mass activity is ~2.2-fold higher than that of Pt/C, which is attributed to the synergistic interaction of the trimetallic electrocatalyst. Furthermore, the specific and mass activities of the synthesized material are maintained after the accelerated stability test, whereas the catalytic properties of Pt/C decreased. These results suggest that the Pt2NiCo/C trimetallic nanocatalyst is a promising candidate cathode electrode for use in PEMFCs.

Pd(II)/Ni(II)-dimethylglyoxime derived Pd‒Ni‒P@N-doped carbon hybrid nanocatalysts for oxygen reduction reaction

Searching for an efficient non‑platinum electrocatalyst for oxygen reduction reaction (ORR) is of great significance for some energy conversion devices. In this work, Pd‒Ni‒P hybrid nanocatalysts loaded on nitrogen-doped carbon supports (defined as Pd‒Ni‒P@NC) are prepared by simply reacting Pd(II)/Ni(II)-dimethylglyoxime with NaH2PO2 at 500 °C. Compared with Pd‒P@NC and Ni‒P@NC counterparts, the Pd‒Ni‒P@NC exhibits a more positive onset potential and higher specific/mass activity towards ORR due to the interfacial coupling interaction between Pd3P0.8 and Ni2P. Moreover, it has a higher catalytic durability and better methanol tolerance than commercial Pt/C catalyst. The surface valence state analysis and electrochemistry characterization reveals that the enhanced electrocatalytic performance of Pd‒Ni‒P@NC is attributed to the modified Pd 3d electronic structure and improved charge transfer character, originating from the incorporation of Ni2P component. Our study provides an alternative non‑platinum electrocatalyst for ORR in fuel cell and metal-air battery.

Versatile synthesis of CuPt nanocatalysts for oxygen reduction reaction

The synthesis of catalysts in the lab is typically limited to low mass quantities, and it makes the large quantity production of catalysts a challenge. The High Energy Ball Milling technique allows for the processing of more massive amounts. In this work, we prepared CuPt nanoparticles, and their oxygen reduction catalytic activity was evaluated. The nanoparticles were prepared by galvanic displacement of Cu coming from a High Energy Ball Milling process. Alumina from the wear of the milling vials was present in the catalyst. Hydrodynamic curves from rotating-disk electrode measurements showed a catalytic activity seven times higher on the alloy than that observed on platinum-loaded carbon black. The catalytic activity was not negatively affected by the presence of the Al2O3 impurities.

First-principles database driven computational neural network approach to the discovery of active ternary nanocatalysts for oxygen reduction reaction.

An elegant machine-learning-based algorithm was applied to study the thermo-electrochemical properties of ternary nanocatalysts for oxygen reduction reaction (ORR). High-dimensional neural network potentials (NNPs) for the interactions among the components were parameterized from big dataset established by first-principles density functional theory calculations. The NNPs were then incorporated with Monte Carlo (MC) and molecular dynamics (MD) simulations to identify not only active, but also electrochemically stable nanocatalysts for ORR in acidic solution. The effects of surface strain caused by selective segregation of certain components on the catalytic performance were accurately characterized. The computationally efficient and precise approach proposes a promising ORR candidate: 2.6 nm icosahedron comprising 60% of Pt and 40% Ni/Cu. Our methodology can be applied for high-throughput screening and designing of key functional nanomaterials to drastically enhance the performance of various electrochemical systems.

Toward High-Performance Pt-Based Nanocatalysts for Oxygen Reduction Reaction through Organic–Inorganic Hybrid Concepts

Pt-based multistructured nanocatalysts such as alloy, core–shell, and surface Pt-rich nanoparticles have been extensively studied for hydrogen fuel cell applications, and their catalytic performances for oxygen reduction reactions have been significantly upgraded for decades. Due to these technical enhancements, Pt-based nanoarchitectures have turned out to be compatible with commercially accessible fuel cell systems. In addition, based on physical and electrochemical backgrounds for the basic catalyst nanoarchitectures, novel catalyst designs with organic–inorganic hybrid concepts have been recently developed to more effectively improve the electrochemical reaction activities and durabilities. In this review, the typical class of Pt-based nanocatalysts are systematically explained according to their compositions and structures, and the emerging class of organic–inorganic hybrid catalyst designs are then thoroughly introduced. It is expected that the most recent improvements of Pt-based nanoarchitectures ...

Functionalized TiO2 Supported Pt Nanocatalysts for Oxygen Reduction Reaction in PEMFCs

The activity and durability of the catalysts used for the oxygen reduction reaction (ORR) are crucial to the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). Pt is still the most common catalytic material for the PEMFCs. Many factors, such as the catalyst’s composition, size, shape, support, and adsorbates, are related to the catalyst’s performance; such matters have been extensively studied over the past several decades in pursuit of high ORR activity, long term stability, and reduced Pt consumption. Titanium oxidebased materials compared to traditional carbon supports have been seen as promising supports for nanosized catalysts in electrochemical applications because of their low cost, nontoxicity, and high stability in acidic and oxidative environments1,2. In this presentation, dual doping of anatase TiO2, used as a Pt catalyst support, both augments resistance against the carbon corrosion that commonly occurs in oxygen reduction reaction (ORR) Pt/C catalysts and promotes the generation of oxygen vacancies that allow better electron transfer from the nanosupport to Pt, thereby facilitating the oxygen dissociation reaction. The effects of the oxygen vacancies within the doped TiO2 nanosupport on ORR activity and stability are investigated both experimentally and by density functional theory analysis. The mass activity of Pt supported doped anatase TiO2 is shown to be 9.1 times higher than that of a commercial standard Pt/C catalyst after hydrogen reduction3. The oxidesupported nanocatalysts also show improved stability against Pt sintering under during cycling, because of strong metal−support interactions (SMSI).

Highly active Pt decorated Pd/C nanocatalysts for oxygen reduction reaction

This article describes findings of the correlation between the atomic scale surface structure and the electrocatalytic performance of nanoengineered Pt-Pd/C catalysts for oxygen reduction reaction (ORR), aiming at providing a new fundamental insight into the role of the detailed atomic decorated structure of the catalysts in fuel cell reactions. Carbon-supported Pt decorated Pd nanoparticles (donated as Pt-Pd/C), with Pt coverage close to a monolayer, were prepared from a simple galvanic replacement reaction between Pd/C particles and PtCl42− at room temperature. The decorated architecture was confirmed by extensive microstructural characterization techniques, including TEM, XRD, XPS, HAADF-STEM, ICP and HS-LEIS. The catalysts were also examined for their intrinsic kinetic activities towards oxygen reduction reaction. The results have shown that the Pt-Pd/C catalysts are highly active towards molecular oxygen electrocatalytic reduction. These findings have profound implications to the design and nanoengineering of decorated surfaces of catalysts for oxygen reduction reaction.

Metal‐Organic Framework‐Derived Non‐Precious Metal Nanocatalysts for Oxygen Reduction Reaction

AbstractBy virtue of diverse structures and tunable properties, metal‐organic frameworks (MOFs) have presented extensive applications including gas capture, energy storage, and catalysis. Recently, synthesis of MOFs and their derived nanomaterials provide an opportunity to obtain competent oxygen reduction reaction (ORR) electrocatalysts due to their large surface area, controllable composition and pore structure. This review starts with the introduction of MOFs and current challenges of ORR, followed by the discussion of MOF‐based non‐precious metal nanocatalysts (metal‐free and metal/metal oxide‐based carbonaceous materials) and their application in ORR electrocatalysis. Current issues in MOF‐derived ORR catalysts and some corresponding strategies in terms of composition and morphology to enhance their electrocatalytic performance are highlighted. In the last section, a perspective for future development of MOFs and their derivatives as catalysts for ORR is discussed.