Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction

Wang, Guanzhi; Yang, Zhenzhong; Du, Yingge; Yang, Yang

doi:10.1002/anie.201907322

Cited by 89 publications

(60 citation statements)

References 54 publications

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“…The porous structure inhibits the aggregation of cobalt ligands at high temperatures, and cobalt species are dispersed as tiny clusters in carbon nanopores. [ 26–28 ]…”

Section: Figurementioning

confidence: 99%

“…The porous structure inhibits the aggregation of cobalt ligands at high temperatures, and cobalt species are dispersed as tiny clusters in carbon nanopores. [26][27][28] High-resolution transmission electron microscopy (HRTEM) and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were also carried out to study the distribution of cobalt clusters in porous carbon. As shown in Figure 1b and Figure S7, Supporting Information, the HRTEM images reveal that the Co/PC samples are mainly composed of porous, highly disordered graphitic carbon particles with diameters of ≈50 nm, and no clear cobalt nanoparticles can be observed.…”

mentioning

confidence: 99%

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Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

et al. 2020

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electrocatalysts to improve their catalytic activity and stability, the realization of a stable and efficient ORR on air electrodes remains a challenge. [4] Generally, advanced metal-air fuel cells require high power output and robust stability. It is vital to build a stable triplephase reaction interface on the electrocatalyst to achieve a perfect balance among electron conduction, oxygen gas diffusion, and ion transportation. [5] However, the masking of active sites in the disorderly stacked electrocatalyst layer in a metalair fuel cell results in sluggish electron transfer. This phenomenon will greatly reduce the efficiency of electron and ion transport, leading to a distinct reduction in the power density. [6] Moreover, the fragile triple-phase interface is easily eroded by water under long-term high current discharging, thereby blocking the oxygen gas transport channel, and causing a significant decline in the stability of the Zn-air fuel cell. [7] To address these issues, the most common strategy is to mix the electrocatalyst and hydrophobic polymer to form a stable three-phase interface and gas transmission channel. In this case, excessive polymer addition greatly increases the reaction resistance and reduces the power density of the Zn-air fuel cell. [8-10] However, fabricating binder-free air electrodes by directly growing electrocatalysts on a conductive substrate can significantly enhance the electrical conductivity. Unfortunately, numerous catalytic sites will be eroded by water flooding in the long-term reaction Metal-air fuel cells with high energy density, eco-friendliness, and low cost bring significantly high security to future power systems. However, the impending challenges of low power density and high-current-density stability limit their widespread applications. In this study, an ultrahigh-power-density Zn-air fuel cell with robust stability is highlighted. Benefiting from the water-resistance effect of the confined nanopores, the highly active cobalt cluster electrocatalysts reside in specific nanopores and possess stable triple-phase reaction areas, leading to the synergistic optimization of electron conduction, oxygen gas diffusion, and ion transport for electrocatalysis. As a result, the as-established Zn-air fuel cell shows the best stability under high-current-density discharging (>90 h at 100 mA cm −2) and superior power density (peak power density: >300 mW cm −2 , specific power: 500 Wg cat −1) compared to most reported non-noble-metal electrocatalysts. The findings will provide new insights in the rational design of electrocatalysts for advanced metal-air fuel cell systems. Metal-air fuel cells are indispensable as next-generation energy storage systems because of their high energy density, eco-friendliness, and low cost. [1] However, the low power density and vulnerable stability of metal-air fuel cells seriously impede their large-scale applications. In particular, a highly efficient and stable power output will be indispensable for emergency backup power supply in future smart po...

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“…The porous structure inhibits the aggregation of cobalt ligands at high temperatures, and cobalt species are dispersed as tiny clusters in carbon nanopores. [ 26–28 ]…”

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

et al. 2020

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“…Extensive efforts have been carried out to obtain control on the shape, exposed facets, [ 7 ] and size of Pt‐Ni bimetallic nanoparticles (NPs); [ 8–11 ] with different elemental composition, [ 12 ] surface composition, [ 13–15 ] and porosity [ 16 ] to enhance the ORR activity and durability with the lowest possible amount of Pt. Therefore, it is extremely important to design the synthesis of shape‐controlled Pt‐Ni NPs toward their potential use in cathode layers of PEMFCs.…”

Section: Introductionmentioning

confidence: 99%

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

Zysler

Zitoun

2020

Part & Part Syst Charact

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this study), leads to difficulty producing scaled-up catalyst quantities sufficient for a PEMFC test.Extensive efforts have been carried out to obtain control on the shape, exposed facets, [7] and size of Pt-Ni bimetallic nanoparticles (NPs); [8][9][10][11] with different elemental composition, [12] surface composition, [13][14][15] and porosity [16] to enhance the ORR activity and durability with the lowest possible amount of Pt. Therefore, it is extremely important to design the synthesis of shape-controlled Pt-Ni NPs toward their potential use in cathode layers of PEMFCs. The syntheses of Pt-Ni NPs have explored a variety of metal precursors, [17] postsynthesis treatment, [18] and dealloying or etching processes [19][20][21][22][23][24] to yield the best electrocatalysts. The ability to tune the morphology by surfactantassisted synthesis [25] has been instrumental in enhancing the mass activity of polyhedral Pt-Ni NPs. The reaction mechanism of growth [26] and etching [27] has been scarcely reported.Solvothermal synthesis usually generates octahedral NPs with high ORR activity of the {111} facets and yield bimetallic nanoparticles with a Pt skeleton and a Ni-rich core. [28] Pt-Ni cuboctahedra nanocrystals with a high activity toward the same reaction have been reported. Cui et al. [13] have reported very high activities. Recently, a very high specific activity has been reported for a well-defined octahedral particle but the rather large particle size (10-15 nm) impedes the mass activity. [29] In this paper, we investigate the structure-properties relationship of Pt 3 Ni NPs with a particle size of 5-6 nm, which is close to the optimal value for ORR electrocatalysts and the lowest reported to still display shape and preferential crystallographic orientation of the facets. We show how a simple synthetic parameter, the ratio between the solution and the free volume in the reactor, leads to the formation of octahedral or cuboctahedral PtNi nanocrystals. Interestingly, each shape displays a different chemical ordering with Pt or Nirich surface, as evidenced by high-angle annular dark-field (HAADF)-high-resolution transmission electron microscopy (HRTEM) mapping. In the case of cuboctahedral NPs, after a few cyclic voltammograms in acidic medium, the NPs retain their geometry but display a Pt-rich skin which explains their ORR activity.Pt 3 Ni stands as one of the most active electrocatalysts for the oxygen reduction reaction (ORR). The activity varies with the morphology of the nanocrystals with a high activity observed for the octahedral shape where only the high density {111} crystallographic planes are exposed. Herein, the synthesis of 6 nm Pt 3 Ni octahedral nanocrystals with a Pt enriched shell or cuboctahedral nanocrystals with a Ni enriched shell is described. Interestingly, the cuboctahedral nanocrystals display a six-pointed star/skeleton of platinum, which features a very uncommon atomic distribution. In the synthesis, a decrease in the oxygen partial pressure induces the transition from octahedral to cub...

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“…The peak at 856.0 eV (Ni 2p 3/2 ) is ascribed to Ni 2 + and the binding energy at 873.6 eV (Ni 2p 1/2 ) is indexed to Ni 3 + . [11,14] The S 2p spectrum ( Figure 3d) presents two bands at 163.7 (S 2p 3/2 ) and 164.5 eV (S 2p 1/2 ), suggesting the existence of S 2À in Ni 3 S 2 . Moreover, the satellite peak at 168.8 eV is ascribed to the high oxidation state sulfur, arising from the oxidation of surface S. [15] The highresolution XPS spectrum of C 1s (Figure 3e) displays three distinct binding energies around 284.6, 285.6 and 288.9 eV correspond to CÀ C, CÀ N/CÀ S and C=O, respectively.…”

Section: Resultsmentioning

confidence: 95%

Construction of Hierarchical 2D PANI/Ni₃S₂ Nanosheet Arrays on Ni Foam for High‐Performance Asymmetric Supercapacitors

Cheng

Yang

Han

et al. 2020

Batteries & Supercaps

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In this work, a hierarchical 2D polyaniline (PANI)/Ni3S2 nanosheet arrays on Ni foam (NF) with open network was successfully developed by the growth of Ni3S2 nanosheet arrays derived from 2D Ni−MOF templates followed by the electrodeposition of a layer of PANI nanoflakes. The as‐prepared PANI/Ni3S2/NF was served as self‐standing supercapacitor electrode. The optimized PANI/Ni3S2/NF‐100 electrode exhibits a high areal capacity of 1.56 mA h cm−2 (487.5 mA h g−1) at 5 mA cm−2 and good rate capability (57.7 % retention at 50 mA cm−2), which significantly outperforms individual PANI/NF or Ni3S2/NF. Furthermore, an asymmetric supercapacitor fabricated by PANI/Ni3S2/NF‐100 and activated carbon electrodes can deliver a high energy density of 48.3 W h kg−1 at a power density of 799.8 W kg−1 with outstanding durability (85.7 % retention of the initial capacity) during 15000 consecutive charge‐discharge cycles. The superior electrochemical performance of PANI/Ni3S2/NF‐100 is attributed to the unique hierarchical PANI/Ni3S2 nanosheet arrays structure. Firstly, the hierarchical open network facilitates the electrolyte ions transport. Secondly, the ultrathin 2D Ni3S2 nanosheets lead to abundant electroactive sites for the Faradaic process, and the conductive PANI layer builds superb highway for fast electron transfer. Thirdly, the free‐standing electrode enables fast redox reaction and low interfacial resistance. Finally, the synergetic effect of Ni3S2 and PANI also contributes to the enhanced capacity.

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Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction

Cited by 89 publications

References 54 publications

Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

Construction of Hierarchical 2D PANI/Ni₃S₂ Nanosheet Arrays on Ni Foam for High‐Performance Asymmetric Supercapacitors

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Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction

Cited by 89 publications

References 54 publications

Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

Octahedral to Cuboctahedral Shape Transition in 6 nm Pt3Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

Construction of Hierarchical 2D PANI/Ni3S2 Nanosheet Arrays on Ni Foam for High‐Performance Asymmetric Supercapacitors

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Octahedral to Cuboctahedral Shape Transition in 6 nm Pt₃Ni Nanocrystals for Oxygen Reduction Reaction Electrocatalysis

Construction of Hierarchical 2D PANI/Ni₃S₂ Nanosheet Arrays on Ni Foam for High‐Performance Asymmetric Supercapacitors