Durable Oxygen Reduction Research Articles

Confined pyrolysis synthesis of N-doped carbon-supported FePr nanoparticles for efficient oxygen reduction based on 3d–4f orbital coupling

To meet the growing demand for new energy storage and conversion technologies, there is an urgent need to prepare highly efficient, economical and durable oxygen reduction catalysts that can replace those based on precious. Herein, N-doped porous carbon supported FePr nanoparticles (FePr/NC) were prepared by confined adsorption and pyrolysis. The characterizations and electrocatalytic properties of the FePr/NC were investigated in details. The prepared FePr/NC catalyst showed excellent oxygen reduction reaction (ORR) catalytic performance with a half-wave potential (E1/2) of 0.87 V in a 0.1 M KOH solution, outperforming commercial Pt/C catalyst (E1/2 = 0.82 V) under the identical conditions. Besides, its onset potential (Eonset) was up to 1.002 V, exceeding the Pt/C (Eonset = 0.92 V). Moreover, the E1/2 only exhibited a negative shift of 7 mV after 2000 cycles, reflecting its significant stability. To understand their exceptional preference for the ORR, the electronic structure of Fe influenced by the doped Pr and the synergistic effect of the FePr nanoparticles with N-doped carbon were investigated. The coupling of Fe's 3d orbitals with Pr's 4 f orbitals in the FePr significantly enhanced the electrocatalytic activity. This work provides a promising strategy for preparation of high-quality transition metal-based carbon catalysts for green energy devices.

MOF-derived three-dimensional porous dodecahedral structured bimetallic Mn/Co-C-N composite for high-performance durable oxygen reduction reaction electrocatalysts

Investigating high-efficiency oxygen reduction reaction (ORR) catalysts is one of the most effective methods for addressing the sluggish kinetics at the fuel cell cathode. Bimetallic three-dimensional porous materials have garnered significant attention due to their diverse structures, large specific surface area and synergistic catalytic effects. Herein, we synthesized a bimetallic three-dimensional porous dodecahedral structure, Mn/Co-C-N, derived from MOF using a straightforward approach. Experimental reults confirm that the strategic incorporation of Mn enhances the electrocatalytic activity for ORR. Meanwhile, the synergistic effects of Mn and Co, as well as the advantages of the dodecahedral structure for expediting electron transfer, all contribute to the exceptional ORR performance. Arc testing in an alkaline electrolyte reveals that the initial potential (Eonset) and the half-wave potential (E1/2) are 0.89 V and 0.80 V, closely approximating those of commercial Pt/C (20 wt%). Following 10 000 stability test cycles, the half-wave potential exhibits a mere 8 mV change, confirming its remarkable stability.

Engineering peripheral S-doped atomic Fe-N4 in defect-rich porous carbon nanoshells for durable oxygen reduction reaction and Zn-air batteries

Iron-nitrogen-carbon (Fe-N-C) single-atom materials have emerged as the most promising catalysts for the oxygen reduction reaction (ORR), which yet suffers from inadequate stability arising from the attack of ·OH and HO2· radicals generated by H2O2. In this study, density functional theory (DFT) calculations reveal that the presence of peripheral S atoms can regulate the electronic structure of the Fe center and suppress the formation of H2O2 to enhance the catalyst's durability. Thereafter, atomic Fe-N4 with peripheral S doping is intricately engineered in defect-rich porous carbon nanoshells (Fe-NS-C) through an adsorption-pyrolysis method. The incorporation of S not only optimizes the coordination microenvironment of Fe-N4 but also induces a larger specific surface area and richer defects. The Fe-NS-C catalyst displays remarkable ORR performance, featuring a half-wave potential (E1/2) of 0.90 V. Its low H2O2 yield (below 1.1 %) and excellent stability (10 mV day in E1/2 after 10,000 cycles) further underscore the superiority of Fe-NS-C. When employed as the cathode for Zn-air battery, Fe-NS-C achieves an impressive peak power density of 230.1 mW cm−2 and stable charge/discharge potentials over an extended duration of 150 h. This study presents an effective strategy for engineering efficient and durable single-atom electrocatalysts for ORR and Zn-air batteries.

Concave Grain Boundaries Stabilized by Boron Segregation for Efficient and Durable Oxygen Reduction.

The oxygen reduction reaction (ORR) is a critical process that limits the efficiency of fuel cells and metal-air batteries due to its slow kinetics, even when catalyzed by platinum (Pt). To reduce Pt usage, enhancing both the specific activity and electrochemically active surface area (ECSA) of Pt catalysts is essential. Here, ultrafine, grain boundary (GB)-rich Pt nanoparticle assemblies are proposed as efficient ORR catalysts. These nanowires offer a large ECSA and a high density of concave GB sites, which improve specific activity. Atoms at these GB sites exhibit increased coordination and lattice distortion, leading to a favorable reduction in oxygen binding energy and enhanced ORR performance. Furthermore, boron segregation stabilizes these GBs, preserving active sites during catalysis. The resulting boron-stabilized Pt nanoassemblies demonstrate ORR specific and mass activities of 9.18 mA cm-2 and 6.40 A mg-1 Pt (at 0.9 V vs. RHE), surpassing commercial Pt/C catalysts by over 35-fold, with minimal degradation after 60000 potential cycles. This approach offers a versatile platform for optimizing the catalytic performance of a wide range of nanoparticle systems.

Challenges and Opportunities in Preparing Fe-N-C Layers Supported on Non-Carbon Supports

Global energy demand will be continuously rising in the foreseeable future. To mitigate the results of climate change it is necessary to reduce the emittance of greenhouse gases. One promising approach is to switch to hydrogen as energy carrier and use proton exchange membrane fuel cells (PEMFCs) to efficiently convert H2 into electric power. Here, hydrogen and oxygen/air are used to directly generate electrical energy with only water as byproduct. Both reactions need to happen efficiently at the same time. The oxygen reduction reaction (ORR), however, is a very sluggish four-electron-reaction and needs efficient catalysts.The state-of-the-art ORR catalyst in PEMFC is platinum but that is a very scarce and expensive metal. Hence, it is important to switch to precious-metal-group (PGM) free catalysts. In recent years, bio inspired iron-based FeNC catalysts have been shown to approach ORR activities that are competitive with those of platinum, even though they need a higher catalyst loading than Pt to reach the desired high current densities.1–3 Those catalysts feature single Fe atoms surrounded by four N atoms in graphitic carbon. The drawback of those materials is their lower stability compared to PGM materials. In a nutshell, the carbon matrix oxidizes during operation in PEMFCs, changing the morphology of the catalytic center and rendering it less active, or inactive, depending on the carbon oxidation extent. Direct demetallation phenomena are also possible, leaving a N4 cavity without metal cation center. It was shown recently by Wu et al.4 that it is possible to raise durability by adding an additional carbon layer on the catalyst. One alternative approach to reduce those degradations is to interface Fe-N4 sites with a carbon-free support. The targeted support material must be immune to corrosion in acid and withstand the typical ORR electrochemical potentials. It also has to be electrically conductive to facilitate electron transfers, both locally and on long scale.In this work, conductive ceramic metal oxide materials (Ta doped SnO2, TTO) was investigated as a possible alternative catalyst supports. This material is resistant to acid and can withstand prolonged potentials at operating conditions in PEMFCs.5 During the synthesis of the FeNC catalysts, high temperatures are generally applied. Such treatments can be detrimental to the conductivity of ceramics due to metal aggregation (in case of doped materials) and may also lead to morphological changes as well as the reduction of the ceramics to metallic materials. A robust method to synthesize FeNC catalysts is by mixing the separate Fe, N and C precursors and using optimized thermal treatment. In this study, the effect of the pyrolysis conditions as well as the ratio of FeNC precursors to TTO was investigated with various characterization methods, e.g. X-ray absorption spectroscopy, Mossbauer spectroscopy, and high resolution TEM. The characterization techniques confirm the presence of single atom Fe as well as different Sn species that might contribute to the activity. The resulting materials were electrochemically characterized with rotating disc electrode techniques and in PEM fuel cells for their ORR-activity and durability. It was shown that the activity of materials with a high FeNC precursor content relative to TTO can outperform a reference FeNC synthesized similarly but without TTO, in both RDE (Figure) and PEMFC.The presentation will report in detail the effects of pyrolysis conditions and FeNC precursor/TTO content on the structure, activity and stability of materials.(1) Mehmood, A. et al. High Loading of Single Atomic Iron Sites in Fe–NC Oxygen Reduction Catalysts for Proton Exchange Membrane Fuel Cells. Nat. Catal. 2022, 5 (4), 311–323. https://doi.org/10.1038/s41929-022-00772-9.(2) Gasteiger, H. A.; Marković, N. M. Just a Dream—or Future Reality? Science 2009, 324 (5923), 48–49. https://doi.org/10.1126/science.1172083.(3) Zion, N. et al.. Electrocatalysis of Oxygen Reduction Reaction in a Polymer Electrolyte Fuel Cell with a Covalent Framework of Iron Phthalocyanine Aerogel. ACS Appl. Energy Mater. 2022, 5 (7), 7997–8003. https://doi.org/10.1021/acsaem.2c00375.(4) Liu, S.et al. Atomically Dispersed Iron Sites with a Nitrogen–Carbon Coating as Highly Active and Durable Oxygen Reduction Catalysts for Fuel Cells. Nat. Energy 2022, 7 (7), 652–663. https://doi.org/10.1038/s41560-022-01062-1.(5) Jiménez-Morales, et al. Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction. ACS Catal. 2020, 10 (18), 10399–10411. https://doi.org/10.1021/acscatal.0c02220. Figure 1

In situ, fast constructing interface/doping-engineered NiCo bimetal-based composites boosting electrocatalytic oxygen reduction for zinc-air battery

Investigating cost-effective, high-performance, stable and durable oxygen reduction reaction (ORR) catalysts is imperative, yet it’s still a formidable obstacle in the advancement of metal-air batteries. In this research, NiCo-bimetallic oxides in situ combined with NiCo-bimetal alloy upon the surface of carbon-based matrix (reduced graphene oxide) (NiCo/Co-NiO/rGO) were synthesized by microwave hydrothermal treatment coupled with an ultrafast Joule heating shock process. The interfacial charge transfer between the bimetal alloy and metal oxide in NiCo/Co-NiO/rGO resulted in electron redistribution at the heterointerface, where *O species migrated to the NiCo alloy surface through Mn+-O-M0 (M=Ni, Co and n=2, 3) bonds, facilitating continuous electron transport between the two phases and unveiling added active sites. Introducing abundant oxygen vacancies by Ni3+ and Co3+ facilitated charge transfer between different valence states and led to forming more active sites, thus significantly enhancing ORR performance. More importantly, solid solution strengthening within the NiCo-bimetallic alloy mitigated the oxidation and corrosion of the catalyst. Therefore, the as-synthesized NiCo/Co-NiO/rGO(5 % Co) exhibited excellent ORR performance under an alkaline medium. It achieved a half-wave potential(E1/2) of 0.85 V(vs. RHE) and maintained 89.10 % of its current density after a 12-h long-term reaction. The assembled zinc-air battery (ZAB) employing this catalyst proved remarkable specific capacity (807.04 mAh·gZn−1), power density (95.54 mW cm−2) and cycling stability (over 240 h), outperforming that of commercial Pt/C+RuO2-based ZAB device. This study presents a viable approach for fabricating low-cost dual transition metal-based catalysts, thereby boosting their electrocatalytic performance and enhancing the efficiency and longevity of metal-air batteries.

Epitaxial growth of highly atomically ordered Pt-Fe nanoparticles from carbon nanotube bundles as durable oxygen reduction electrocatalysts

Intermetallic Pt-based nanoparticles have displayed excellent activity for the oxygen reduction reaction (ORR) in fuel cells. However, it remains a great challenge to synthesize highly atomically ordered Pt-based nanoparticle catalysts because the formation of an atomically ordered structure usually requires high-temperature annealing accompanied by grain sintering. Here we report the direct epitaxial growth of well-aligned, highly atomically ordered Pt3Fe and PtFe nanoparticles (<5 nm) on single-walled carbon nanotube (SWCNT) bundles films. The long-range periodically symmetric van der Waals (vdW) interactions between SWCNT bundles and Pt-Fe nanoparticles play an important role in promoting not only the alignment ordering of inter-nanoparticles but also the atomic ordering of intra-nanoparticles. The ordered Pt3Fe/SWCNT catalyst showed enhanced ORR catalytic performance of 2.3-fold higher mass activity and 3.1-fold higher specific activity than commercial Pt/C. Moreover, the formation of an interlocked interface and strong vdW interaction endow the Pt-Fe/SWCNT catalysts with extreme long-term stability in potential cycling and excellent anti-thermal sintering ability.

Regulation of d‐Orbital Electron in Fe‐N4 by High‐Entropy Atomic Clusters for Highly Active and Durable Oxygen Reduction Reaction

AbstractSimultaneously improving activity and stability is a crucial yet challenge in the development of metallic single‐atom‐based catalysts. In current work, a novel approach is introduced to address this issue by combining post‐adsorption and secondary pyrolysis techniques to create a synergistic catalytic system, in which the single atoms (SAs) Fe sites played in the NC matrix (Fe─NC) are coupled with high‐entropy atomic clusters (HEACs). Theoretical calculations reveal that the incorporation of HEACs lead to a rehybridization of the 3d orbital configuration of Fe‐N4, which helps to balance the adsorption/desorption energy of oxygenated intermediates. In situ spectroscopy further reveals that the rate‐limiting step of OH* desorption on HEAC/Fe─NC in oxygen reduction reaction (ORR) is more facile compared to atomic Fe─NC, implying a higher ORR activity. Moreover, the synergistic effect of diffusion activation barriers and configuration entropy contributes to the structural stability of HEAC/Fe─NC, resulting in remarkable durability. Consequently, this unique catalyst exhibits half‐wave potentials of 0.927 and 0.828 V in an aqueous solution of KOH (0.1 m) and HClO4 (0.1 m), respectively, along with excellent durability. The findings propose a novel strategy for modulating the electronic structure of metallic SAs catalysts and enhancing their stability through strong interactions between SAs and HEACs.

Ti Single Atom Enhancing Pt‐Based Intermetallics for Efficient and Durable Oxygen Reduction

AbstractThe insufficient durability of Pt‐based catalysts and the sluggish kinetics of oxygen reduction reaction (ORR) is hampering the development of proton exchange membrane fuel cells (PEMFCs) for commercialization. Herein, a single atom Ti‐modified activated nitrogen‐doped porous carbon (Ti‐a‐NPC) is designed to equalize O2‐activation/*OH‐removal through regulating the charge rearrangement of ultra‐small L12‐Pt3Co for efficient and durable oxygen reduction. The Ti single‐atom modified in the surface/pore of Ti‐a‐NPC can anchor the Pt‐based intermetallic nanoparticles (NPs) not only guarantees Pt‐based intermetallics’ ultra‐fine size (≈2.62 nm) but also maintains Pt‐based intermetallics during ORR process. The enhanced catalyst (L12‐Pt3Co/Ti‐a‐NPC) achieves 11‐fold mass activity (1.765 A mgPt−1) compared to commercial Pt/C. Notably, after 30 000 cycles of accelerated durability tests, the mass activity of the L12‐Pt3Co/Ti‐a‐NPC only decreased by 3.7%, while that of commercial Pt/C decreased by 37.1%. Rationalized by theoretical simulation, the introduction of Ti atoms can form charge channels between L12‐Pt3Co NPs and Ti‐a‐NPC, accelerating the charge transfer in the ORR process. Furthermore, the charge of L12‐Pt3Co will accumulate to Ti atoms and buffer the electron transfer of L12‐Pt3Co to the N atoms, thus optimizing the adsorption performance of the active site to the oxygen‐containing intermediate and improving the intrinsic activity of the catalyst.

Efficient and durable oxygen reduction in alkaline media by doping heteroatomic boron into FeSA-NC catalyst

Despite extensive research has been conducted on atomic dispersion catalysts for various reactions, altering the electronic structure of the central metal to enhance electrochemical reactivity remains a challenging task. Herein, the electrochemical reactivity was considerably enhanced by introducing heteroatomic B to adjust the d-band of single Fe center. In specific, the obtained FeSA-BNC catalyst demonstrated an outstanding ORR performance (E1/2 = 0.87 V) and exhibited greater long-term durability in alkaline media compared to Pt/C. The performance of FeSA-BNC in Zn–air battery was also higher than that of Pt/C. According to theoretical calculations, a downward shift in the d-band center of Fe was induced by introducing B, thereby improving the desorption of intermediates and facilitating the oxygen reduction reaction (ORR).

Strong Interaction between Titanium Carbonitride Embedded in Mesoporous Carbon Nanofibers and Pt Enables Durable Oxygen Reduction.

Platinum (Pt) supported on high surface area carbon has been the most widely used electrocatalyst in proton exchange membrane fuel cell (PEMFC). However, conventional carbon supports are susceptible to corrosion at high potentials, leading to severe degradation of electrochemical performance. In this work, titanium carbonitride embedded in mesoporous carbon nanofibers (m-TiCN NFs) are reported as a promising alternative to address this issue. Benefiting from the interpenetrating conductive pathways inside the one-dimensional (1D) nanostructures and the embedded TiCN nanoparticles (NPs), m-TiCN NFs exhibit excellent stability at high potentials and interact strongly with Pt NPs. Subsequently, m-TiCN NFs-supported Pt NPs deliver remarkably enhanced oxygen reduction reaction (ORR) activity and durability, with negligible activity decay and less than 5% loss of electrochemical surface area（ECSA） after 50000 cycles. Moreover, the fuel cell assembled by this catalyst delivers a maximum power density of 1.22W cm-2 and merely 3% loss after 30000 cycles of accelerated durability tests under U.S. Department of Energy (DOE) protocols. The improved ORR activity and durability are attributed to the superior corrosion resistance of the m-TiCN NF support and the strong interaction between Pt and m-TiCN NFs.

Atomic controlled shell thickness on Pt@Pt3Ti core-shell nanoparticles for efficient and durable oxygen reduction

The exploitation of durable and highly active Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is essential for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, we designed Pt@Pt3Ti core-shell nanoparticles with atomic-controllable shells through precise thermal diffusing Ti into Pt nanoparticles for effective and durable ORR. Combining theoretical and experiment analysis, we found that the lattice strain of Pt3Ti shells can be tailored by precisely controlling the thickness of Pt3Ti shell in atomic-scale on account of the lattice constant difference between Pt and Pt3Ti to optimize adsorption properties of Pt3Ti for ORR intermediates, thus enhancing its performance. The Pt@Pt3Ti catalyst with one-atomic Pt3Ti shell (Pt@1L-Pt3Ti/TiO2-C) demonstrates excellent performance with mass activity of 592 mA mgPt−1 and durability nearly 19.5-fold that of commercial Pt/C with negligible decay (2 %) after 30,000 potential cycles (0.6–1.0 V vs. RHE). Notably, at higher potential cycles (1.0 V-1.5 V vs. RHE), Pt@1L-Pt3Ti/TiO2-C also showed far superior durability than Pt/C (9.6 % decayed while 54.8 % for commercial Pt/C). This excellent stability is derived from the intrinsic stability of Pt3Ti alloy and the confinement effect of TiO2-C. The catalyst’s enhancement was further confirmed in PEMFC configuration.

Iron-nitrogen co-doped carbon nanospheres prepared by template-free melting salt-assisted pyrolysis as efficient and durable oxygen reduction catalysts

It is necessary to seek oxygen reduction reactions (ORRs) electrocatalyst that can replace commercial Pt/C for new energy conversion devices. Herein, we used molten salt-assisted pyrolysis to successfully convert small nitrogen-containing carbon molecules directly into iron-nitrogen codoped carbon nanospheres (Fe–N–Cs) without the need for external templates. Molten salts provide a solvo-like environment for the high-temperature pyrolysis of small carbon molecules and bulk oxides. Small molecules containing nitrogen and carbon are subjected to spatial domain-limiting effect, reducing volatilization in the calcination processes. Besides, the strong polarity provided by molten salts can not only dissolve bulk oxides but also prevent free metal atoms from gathering again to form particles or clusters. The synthesized Fe–N–Cs exhibit excellent ORR activity. The half wave potential (E1/2, 0.67 V vs. RHE) in acidic solution is almost equivalent to Pt/C. Furthermore, Fe–N–Cs have the ability to prevent methanol poisoning and its stability is strong.

Multiscale Regulation of Ordered PtCu Intermetallic Electrocatalyst for Highly Durable Oxygen Reduction Reaction.

Transforming the Pt-M alloy into an ordered intermetallic is an effective strategy to improve the electrocatalytic activity and stability toward the oxygen reduction reaction (ORR). However, the synthesis of nanosized intermetallics remains challenging. Herein, we report an efficient ORR electrocatalyst, consisting of a monodisperse nanosized PtCu intermetallic on hollow mesoporous carbon spheres (HMCS). As predicted by theoretical calculations, PtCu intermetallics exhibit beneficial electronic structure, with a low theoretical overpotential of 0.33 V and enhanced Cu stability. Resulting from the multiscale modulation of catalyst structure, the O-PtCu/HMCS catalyst delivers a high mass activity of 2.73 A cm-2Pt at 0.9 V and remarkable stability. Identical location transmission electron microscopy (IL-TEM) investigations demonstrate that the rate of carbon corrosion is alleviated on HMCS, which contributes to the long-term durability. This work provides a promising design strategy for an ORR electrocatalyst, and the IL-TEM investigations offer new perspectives for the performance enhancement mechanism.

High entropy La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 with tailored eg occupancy and transition metal-oxygen bond properties for oxygen reduction reaction

Forming high entropy oxide provides a feasible approach to finding a balance among moderate eg occupancy, high transition metal-oxygen (TM-O) covalency, and lattice energy, which is essential to ensure efficient and durable oxygen reduction reaction (ORR) process for perovskite lanthanide-transition metal oxides (LaTMO3). However, due to the compositional complexity, clarifying the relevance among the high entropy components, eg occupancy, TM-O properties, and ORR performance still remains a challenge. Herein, adopting the B site entropy-driven strategy, a series of LaTMO3 (TM = Cr, Mn, Fe, Co, Ni) with tunable eg occupancy and TM-O bond properties are synthesized, and the correlations between high entropy elements, eg occupancy, TM-O properties, and ORR performances are revealed quantitively based on the crystal field theory and the Phillips–Van Vechten–Levine (P–V–L) valence bond theory. High entropy La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 delivers a low overpotential of 493 mV (vs. 503 mV for LaMnO3) and a minuscule decline by only 1.7% (vs. 4.4% for LaMnO3) in half wave potential after 10,000 cycles, which can be associated with the tailored eg occupancy (1.06) and the significant enhancement in both TM-O covalency (4%) and lattice energy (691.75 kJ mol–1). This work not only demonstrates the prospects of high entropy LaTMO3 in the ORR field but also provides a new perspective for the quantitative analysis of the structure-activity relationship for high entropy oxide ORR catalysts.

Mo-Based MXene-Supported Pt Nanoparticles for Highly Durable Oxygen Reduction in Acidic Electrolytes

Mo-Based MXene-Supported Pt Nanoparticles for Highly Durable Oxygen Reduction in Acidic Electrolytes

Collective Effect in a Multicomponent Ensemble Combining Single Atoms and Nanoparticles for Efficient and Durable Oxygen Reduction

AbstractMetal single‐atom catalysts represent one of the most promising non‐noble metal catalysts for the oxygen reduction reaction (ORR). However, they still suffer from insufficient activity and, particularly, durability for practical applications. Leveraging density functional theory (DFT) and machine learning (ML), we unravel an unexpected collective effect between FeN4OH sites, CeN4OH motifs, Fe nanoparticles (NPs), and Fe−CeO2 NPs. The collective effect comprises differently‐weighted electronic and geometric interactions, whitch results in significantly enhanced ORR activity for FeN4OH active sites with a half‐wave potential (E1/2) of 0.948 V versus the reversible hydrogen electrode (VRHE) in alkaline, relative to a commercial Pt/C (E1/2, 0.851 VRHE). Meanwhile, this collective effect endows the shortened Fe−N bonds and the remarkable durability with negligible activity loss after 50,000 potential cycles. The ML was used to understand the intricate geometric and electronic interactions in collective effect and reveal the intrinsic descriptors to account for the enhanced ORR performance. The universality of collective effect was demonstrated effective for the Co, Ni, Cu, Cr, and Mn‐based multicomponent ensembles. These results confirm the importance of collective effect to simultaneously improve catalytic activity and durability.

Collective Effect in a Multicomponent Ensemble Combining Single Atoms and Nanoparticles for Efficient and Durable Oxygen Reduction.

Metal single-atom catalysts represent one of the most promising non-noble metal catalysts for the oxygen reduction reaction (ORR). However, they still suffer from insufficient activity and, particularly, durability for practical applications. Leveraging density functional theory (DFT) and machine learning (ML), we unravel an unexpected collective effect between FeN4OH sites, CeN4OH motifs, Fe nanoparticles (NPs), and Fe-CeO2 NPs. The collective effect comprises differently-weighted electronic and geometric interactions, whitch results in significantly enhanced ORR activity for FeN4OH active sites with a half-wave potential (E1/2) of 0.948 V versus the reversible hydrogen electrode (VRHE) in alkaline, relative to a commercial Pt/C (E1/2, 0.851 VRHE). Meanwhile, this collective effect endows the shortened Fe-N bonds and the remarkable durability with negligible activity loss after 50,000 potential cycles. The ML was used to understand the intricate geometric and electronic interactions in collective effect and reveal the intrinsic descriptors to account for the enhanced ORR performance. The universality of collective effect was demonstrated effective for the Co, Ni, Cu, Cr, and Mn-based multicomponent ensembles. These results confirm the importance of collective effect to simultaneously improve catalytic activity and durability.

Noble metal-free FeCoNiMnV high entropy alloy anchored on N-doped carbon nanotubes with prominent activity and durability for oxygen reduction and zinc–air batteries

Efficient and stable oxygen reduction reaction (ORR) catalysts are essential for constructing reliable energy conversion and storage devices. Herein, we prepared noble metal-free FeCoNiMnV high-entropy alloy supported on nitrogen-doped carbon nanotubes (FeCoNiMnV HEA/N-CNTs) by a one-step pyrolysis at 800 °C, as certificated by a set of characterizations. The graphitization degree of the N-CHTs was optimized by tuning the pyrolysis temperature in the control groups. The resultant catalyst greatly enhanced the ORR characteristics in the alkaline media, showing the positive onset potential (Eonset) of 0.99 V and half-wave potential (E1/2) of 0.85 V. More importantly, the above FeCoNiMnV HEA/N-CNTs assembled Zn-air battery exhibited a greater open-circuit voltage (1.482 V), larger power density (185.12 mW cm−2), and outstanding cycle stability (1698 cycles, 566 h). This study provides some valuable insights on developing sustainable ORR catalysts in Zn-air batteries.

A sub-4 nm PtCu3 intermetallic catalyst with an L12-ordered structure toward efficient activity and durability for oxygen reduction

Pt-based intermetallic alloys have shown bright prospects for promoting the activity and durability of fuel cell cathode oxygen reduction.