Constructing monodispersed metal sites in heterocatalysis is an efficient strategy to boost their catalytic performance. Herein, a new strategy using monodispersed metal sites to tailor Pt‐based ...nanocatalysts is addressed by engineering unconventional p–d orbital hybridization. Thus, monodispersed Ga on Pt3Mn nanocrystals (Ga‐O‐Pt3Mn) with high‐indexed facets was constructed for the first time to drive ethanol electrooxidation reaction (EOR). Strikingly, the Ga‐O‐Pt3Mn nanocatalyst shows an enhanced EOR performance with achieving 8.41 times of specific activity than that of Pt/C. The electrochemical in situ Fourier transform infrared spectroscopy results and theoretical calculations disclose that the Ga‐O‐Pt3Mn nanocatalyst featuring an unconventional p–d orbital hybridization not only promote the C−C bond‐breaking and rapid oxidation of ‐OH of ethanol, but also inhibit the generation of poisonous CO intermediate species. This work discloses a promising strategy to construct a novel nanocatalysts tailored by monodispersed metal site as efficient fuel cell catalysts.
The monodispersed Ga site tailored Pt3Mn nanocatalyst based on high‐indexed facets was constructed and shows excellent EOR performance with high activity and selectivity towards the C2 reaction pathway, which was attributed to the unconventional p–d orbital hybridization and atomic‐level interface synergy.
Binders have been reported to play a key role in improving the cycle performance of Si anode materials of lithium‐ion batteries. In this study, the biopolymer guar gum (GG) is applied as the binder ...for a silicon nanoparticle (SiNP) anode of a lithium‐ion battery for the first time. Due to the large number of polar hydroxyl groups in the GG molecule, a robust interaction between the GG binder and the SiNPs is achieved, resulting in a stable Si anode during cycling. More specifically, the GG binder can effectively transfer lithium ions to the Si surface, similarly to polyethylene oxide solid electrolytes. When GG is used as a binder, the SiNP anode can deliver an initial discharge capacity as high as 3364 mAh g−1, with a Coulombic efficiency of 88.3% at the current density of 2100 mA g−1, and maintain a capacity of 1561 mAh g−1 after 300 cycles. The study shows that the electrochemical performance of the SiNP anode with GG binder is significantly improved compared to that of a SiNP anode with a sodium alginate binder, and it demonstrates that GG is a promising binder for Si anodes of lithium‐ion batteries.
Guar gum is used as a robust binder for a silicon nanoparticle anode of a lithium‐ion battery for the first time. With a large number of polar hydroxyl groups, the guar gum binder can provide effective transport pathways for lithium ions, which significantly improves the electrochemical performance.
Defects have been found to enhance the electrocatalytic performance of NiFe‐LDH for oxygen evolution reaction (OER). Nevertheless, their specific configuration and the role played in regulating the ...surface reconstruction of electrocatalysts remain ambiguous. Herein, cationic vacancy defects are generated via aprotic‐solvent‐solvation‐induced leaking of metal cations from NiFe‐LDH nanosheets. DFT calculation and in situ Raman spectroscopic observation both reveal that the as‐generated cationic vacancy defects tend to exist as VM (M=Ni/Fe); under increasing applied voltage, they tend to assume the configuration VMOH, and eventually transform into VMOH‐H which is the most active yet most difficult to form thermodynamically. Meanwhile, with increasing voltage the surface crystalline Ni(OH)x in the NiFe‐LDH is gradually converted into disordered status; under sufficiently high voltage when oxygen bubbles start to evolve, local NiOOH species become appearing, which is the residual product from the formation of vacancy VMOH‐H. Thus, we demonstrate that the cationic defects evolve along with increasing applied voltage (VM → VMOH → VMOH‐H), and reveal the essential motif for the surface restructuration process of NiFe‐LDH (crystalline Ni(OH)x → disordered Ni(OH)x → NiOOH). Our work provides insight into defect‐induced surface restructuration behaviors of NiFe‐LDH as a typical precatalyst for efficient OER electrocatalysis.
Along with increasing voltage during the OER process, the structural evolution of cationic defects within NiFe‐LDH, where the simple vacancy VM changes to VMOH and then to the most reactive VMOH‐H, and the surface restructuration, where surface crystalline Ni(OH)x is converted to disordered Ni(OH)x and then to the surface local NiOOH species, are voltage‐regulated concurrent events defining the eventual catalytic performance of the precatalyst.
Metal‐containing nanoparticles (M‐NPs) in metal/nitrogen‐doped carbon (M‐N‐C) catalysts have been considered hostile to the acidic oxygen reduction reaction (ORR). The relation between M‐NPs and the ...active sites of metal coordinated with nitrogen (MNx) is hard to establish in acid medium owing to the poor stability of M‐NPs. Herein, we develop a strategy to successfully construct a new FeCo‐N‐C catalyst containing highly active M‐NPs and MN4 composite sites (M/FeCo‐SAs‐N‐C). Enhanced catalytic activity and stability of M/FeCo‐SAs‐N‐C is shown experimentally. Calculations reveal that there is a strong interaction between M‐NPs and FeN4 sites, which can favor ORR by activating the O−O bond, thus facilitating a direct 4 e− process. Those findings firstly shed light on the highly active M‐NPs and FeN4 composite sites for catalyzing acid oxygen reduction reaction, and the relevant reaction mechanism is suggested.
Highly active metal‐containing nanoparticles and FeN4 composite sites have been constructed. Experiment and calculation results reveal the enormous potential for activating the O−O bond and promoting the direct 4 e− dissociation pathway in the acidic oxygen reduction reaction (ORR), which could fundamentally improve ORR activity and inhibit the formation of reactive oxygen species.
Lithium-sulfur batteries are attractive alternatives to lithium-ion batteries because of their high theoretical specific energy and natural abundance of sulfur. However, the practical specific energy ...and cycle life of Li-S pouch cells are significantly limited by the use of thin sulfur electrodes, flooded electrolytes and Li metal degradation. Here we propose a cathode design concept to achieve good Li-S pouch cell performances. The cathode is composed of uniformly embedded ZnS nanoparticles and Co-N-C single-atom catalyst to form double-end binding sites inside a highly oriented macroporous host, which can effectively immobilize and catalytically convert polysulfide intermediates during cycling, thus eliminating the shuttle effect and lithium metal corrosion. The ordered macropores enhance ionic transport under high sulfur loading by forming sufficient triple-phase boundaries between catalyst, conductive support and electrolyte. This design prevents the formation of inactive sulfur (dead sulfur). Our cathode structure shows improved performances in a pouch cell configuration under high sulfur loading and lean electrolyte operation. A 1-A-h-level pouch cell with only 100% lithium excess can deliver a cell specific energy of >300 W h kg
with a Coulombic efficiency >95% for 80 cycles.
P2-type sodium manganese-rich layered oxides are promising cathode candidates for sodium-based batteries because of their appealing cost-effective and capacity features. However, the structural ...distortion and cationic rearrangement induced by irreversible phase transition and anionic redox reaction at high cell voltage (i.e., >4.0 V) cause sluggish Na-ion kinetics and severe capacity decay. To circumvent these issues, here, we report a strategy to develop P2-type layered cathodes via configurational entropy and ion-diffusion structural tuning. In situ synchrotron X-ray diffraction combined with electrochemical kinetic tests and microstructural characterizations reveal that the entropy-tuned Na
Mn
Ni
Cu
Mg
Ti
O
(CuMgTi-571) cathode possesses more {010} active facet, improved structural and thermal stability and faster anionic redox kinetics compared to Na
Mn
Ni
O
. When tested in combination with a Na metal anode and a non-aqueous NaClO
-based electrolyte solution in coin cell configuration, the CuMgTi-571-based positive electrode enables an 87% capacity retention after 500 cycles at 120 mA g
and about 75% capacity retention after 2000 cycles at 1.2 A g
.
The development of electrocatalysts capable of efficient reduction of nitrate (NO
) to ammonia (NH
) is drawing increasing interest for the sake of low carbon emission and environmental protection. ...Herein, we present a CuCo bimetallic catalyst able to imitate the bifunctional nature of copper-type nitrite reductase, which could easily remove NO
via the collaboration of two active centers. Indeed, Co acts as an electron/proton donating center, while Cu facilitates NO
adsorption/association. The bio-inspired CuCo nanosheet electrocatalyst delivers a 100 ± 1% Faradaic efficiency at an ampere-level current density of 1035 mA cm
at -0.2 V vs. Reversible Hydrogen Electrode. The NH
production rate reaches a high activity of 4.8 mmol cm
h
(960 mmol g
h
). A mechanistic study, using electrochemical in situ Fourier transform infrared spectroscopy and shell-isolated nanoparticle enhanced Raman spectroscopy, reveals a strong synergy between Cu and Co, with Co sites promoting the hydrogenation of NO
to NH
via adsorbed *H species. The well-modulated coverage of adsorbed *H and *NO
led simultaneously to high NH
selectivity and yield.
Toward the pursuit of high-performance Ni2+/Co2+/Fe3+-relevant oxygen evolution reaction (OER) electrocatalysts, the modulation of local electronic structure of the active metal sites provides the ...fundamental motif, which could be achieved either through direct modifications of local chemical environment or interfacial interaction with a second metal substrate which possesses high electronegativity (typically noble metal Au). Herein, we report that the local electronic structure of Ni–Fe layered double hydroxide (LDH) could be favorably modulated through strong interfacial interactions with FeOOH nanoparticles (NPs). The biphasic and multiscale composites FeOOH/LDH demonstrated an increasingly pronounced synergy effect for OER catalysis when the average size of FeOOH NPs decreases from 18.0 to 2.0 nm. Particularly, the composite with average size of FeOOH NPs of 2.0 nm exhibited an overpotential of 174 mV at 10 mA cm–2 and a tafel slope of 27 mV dec–1 in 1.0 M KOH, outmatching all the noble and non-noble OER catalysts reported so far; it also operates smoothly in various stability tests. A mechanistic study based on XANES and EXAFS analysis, d.c. voltammetry and large amplitude Fourier Transformed a.c. voltammetry proved the presence of high-oxidation-state Fe(3+δ)+sites with relatively short Fe(3+δ)+–O bond from the highly unsaturated ultrafine FeOOH NPs which could reform the local electronic structure and favorably manipulate the electronic oxidation and thus electrocatalytic behaviors of the Ni2+ species in the Ni–Fe LDH, hence leading to the easy formation, excellent OER activity, and extraordinary structural and catalytic stability. Our work puts an emphasis on the role of the solid–solid interfacial chemistry between a Ni–Fe LDH and a non-noble-metal component in engineering the local electronic structure of the active metal sites, which successfully pushed forward the catalytic activity of the well-studied Ni–Fe LDH far beyond its current limit in OER catalysis and opened up an avenue for rational design of OER electrocatalysts.
Driven by the persisting poor understanding of the sluggish kinetics of the hydrogen evolution reaction (HER) on Pt in alkaline media, a direct correlation of the interfacial water structure and ...activity is still yet to be established. Herein, using Pt and Pt–Ni nanoparticles we first demonstrate a strong dependence of the proton donor structure on the HER activity and pH. The structure of the first layer changes from the proton acceptors to the donors with increasing pH. In the base, the reactivity of the interfacial water varied its structure, and the activation energies of water dissociation increased in the sequence: the dangling O−H bonds < the trihedrally coordinated water < the tetrahedrally coordinated water. Moreover, optimizing the adsorption of H and OH intermediates can re‐orientate the interfacial water molecules with their H atoms pointing towards the electrode surface, thereby enhancing the kinetics of HER. Our results clarified the dynamic role of the water structure at the electrode–electrolyte interface during HER and the design of highly efficient HER catalysts.
On nickel–platinum alloy nanoparticles under alkaline conditions, the reactivity of interfacial water varies with its structure and the order of water dissociation. The inclusion of nickel re‐orientates interfacial water molecules with their hydrogen atoms pointing towards the electrode surface, thereby enhancing the kinetics of the hydrogen evolution reaction (HER).
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