With high energy density and low material cost, lithium-sulfur batteries (LSBs) emerge quite expeditiously as a fascinating energy storage system over the past decade. Broad applications of LSBs ...ranging from electric vehicles to stationary grid storage seem rather bright in recent literatures. However, there still exist many pressing challenges to be addressed because we do not yet fully understand and control the electrode-electrolyte interface chemistries during battery operation, such as polysulfide shuttling and poor utilization of active sulfur. Single-atom catalysts (SACs) pave new possibilities of tackling the tough issues due to their decent applicability in the atomic-level identification of structure-activity relationships and reaction mechanism, as well as their structural tunability with atomic precision. This review comprehensively summarizes the very recent advances in utilization of highly active SACs for LSBs by stating and discussing the related publications, which involves catalyst synthesis routes, battery performance, catalytic mechanisms, optimization strategies, and promises to achieve long-life, high-energy LSBs. We see that endeavors to employ SACs to modify sulfur cathode have allowed efficient polysulfide conversion and confinement, leading to the minimization of shuttle effect. Parallel efforts are being devoted to extending the scope of SACs to cell separator and lithium metal anode in order to unlock the full potential of LSBs. We also obtain mechanistic insights into battery chemistries and nature of SACs in their strong interactions with polysulfides through advanced
in situ
characterizations documented. Overall, acceleration in the development of LSBs by introducing SACs is noticeable, and this cutting edge needs more attentions to further promoting the design of better LSBs.
Abstract
Metallic tungsten disulfide (WS
2
) monolayers have been demonstrated as promising electrocatalysts for hydrogen evolution reaction (HER) induced by the high intrinsic conductivity, however, ...the key challenges to maximize the catalytic activity are achieving the metallic WS
2
with high concentration and increasing the density of the active sites. In this work, single-atom-V catalysts (V SACs) substitutions in 1T-WS
2
monolayers (91% phase purity) are fabricated to significantly enhance the HER performance via a one-step chemical vapor deposition strategy. Atomic-resolution scanning transmission electron microscopy (STEM) imaging together with Raman spectroscopy confirm the atomic dispersion of V species on the 1T-WS
2
monolayers instead of energetically favorable 2H-WS
2
monolayers. The growth mechanism of V SACs@1T-WS
2
monolayers is experimentally and theoretically demonstrated. Density functional theory (DFT) calculations demonstrate that the activated V-atom sites play vital important role in enhancing the HER activity. In this work, it opens a novel path to directly synthesize atomically dispersed single-metal catalysts on metastable materials as efficient and robust electrocatalysts.
Intricate hollow structures garner tremendous interest due to their aesthetic beauty, unique structural features, fascinating physicochemical properties, and widespread applications. Here, the recent ...advances in the controlled synthesis are discussed, as well as applications of intricate hollow structures with regard to energy storage and conversion. The synthetic strategies toward complex multishelled hollow structures are classified into six categories, including well‐established hard‐ and soft‐templating methods, as well as newly emerging approaches based on selective etching of “soft@hard” particles, Ostwald ripening, ion exchange, and thermally induced mass relocation. Strategies for constructing structures beyond multishelled hollow structures, such as bubble‐within‐bubble, tube‐in‐tube, and wire‐in‐tube structures, are also covered. Niche applications of intricate hollow structures in lithium‐ion batteries, Li–S batteries, supercapacitors, Li–O2 batteries, dye‐sensitized solar cells, photocatalysis, and fuel cells are discussed in detail. Some perspectives on the future research and development of intricate hollow structures are also provided.
Intricate hollow structures attract tremendous interest due to their aesthetic beauty, unique structural features, fascinating physicochemical properties, and widespread applications. A comprehensive overview on the controlled synthesis of intricate hollow structures is given, along with their niche applications in secondary batteries, supercapacitors, dye‐sensitized solar cells, photocatalysis, and fuel cells.
High-entropy alloys have received considerable attention in the field of catalysis due to their exceptional properties. However, few studies hitherto focus on the origin of their outstanding ...performance and the accurate identification of active centers. Herein, we report a conceptual and experimental approach to overcome the limitations of single-element catalysts by designing a FeCoNiXRu (X: Cu, Cr, and Mn) High-entropy alloys system with various active sites that have different adsorption capacities for multiple intermediates. The electronegativity differences between mixed elements in HEA induce significant charge redistribution and create highly active Co and Ru sites with optimized energy barriers for simultaneously stabilizing OH
and H
intermediates, which greatly enhances the efficiency of water dissociation in alkaline conditions. This work provides an in-depth understanding of the interactions between specific active sites and intermediates, which opens up a fascinating direction for breaking scaling relation issues for multistep reactions.
Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A ...Schottky catalyst based on metal–semiconductor junction principles is presented. With metallic MoB, the introduction of n‐type semiconductive g‐C3N4 induces a vigorous charge transfer across the MoB/g‐C3N4 Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec−1 and a high exchange current density of 17 μA cm−2, which is far better than that of pristine MoB. First‐principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation.
Schottky catalyst: The hydrogen evolution activity of a metallic MoB catalyst can be significantly promoted by enhancing the surface charge density across a Schottky contact with an n‐type semiconductor.
Defect engineering is one of the effective strategies to optimize the physical and chemical properties of molybdenum disulfide (MoS
2
) to improve catalytic hydrogen evolution reaction (HER) ...performance. Dislocations, as a typical defect structure, are worthy of further investigation due to the versatility and sophistication of structures and the influence of local strain effects on the catalytic performance. Herein, this study adopted a low-temperature hydrothermal synthesis strategy to introduce numerous dislocation-strained structures into the in-plane and out-of-plane of MoS
2
nanosheets. Superior HER catalytic activity of 5.85 mmol·g
−1
·h
−1
under visible light was achieved based on the high-density dislocations and the corresponding strain field. This work paves a new pathway for improving the catalytic activity of MoS
2
via a dislocation-strained synergistic modulation strategy.
Herein, a graphene oxide (GO)-wired manganese silicate (MS) hollow sphere (MS/GO) composite is successfully synthesized. Such an architecture possesses multiple advantages in lithium and sodium ...storage. The hollow MS structure provides a sufficient free space for volume variation accommodation; the porous and low-crystalline features facilitate the diffusion of lithium ions; meanwhile, the flexible GO sheets enhance the electronic conductivity of the composite to a certain degree. When applied as the anode material for lithium-ion batteries (LIBs), the as-obtained MS/GO composite exhibits a high reversible capacity, ultrastable cyclability, and good rate performance. Particularly, the MS/GO composite delivers a high capacity of 699 mA h g–1 even after 1000 cycles at 1 A g–1. The sodium-storage performance of MS/GO has been studied for the first time, and it delivers a stable capacity of 268 mA h g–1 after 300 cycles at 0.2 A g–1. This study suggests that the rational design of metal silicates would render them promising anode materials for LIBs and SIBs.
Porous carbons have been extensively studied in supercapacitors. However, it remains a grand challenge for porous carbons to achieve a volumetric capacitance (C v) of over 200 F cm–3 because of the ...low intrinsic density and limited capacitance. Herein, we propose a pomegranate-like carbon microsphere (PCS) constructed by monodisperse, submicron, N-doped microporous carbon spheres for high-volumetric-capacitance supercapacitors. The assembly of submicron carbon spheres into pomegranate-like structures significantly reduces the required binder amount (2.0 wt %) for electrode preparation, diminishes the interparticle resistance, and most importantly, endows the PCS with a high packing density (0.75 g cm–3). Benefited from the high surface area (1477 m2 g–1), N-doping (3.0 wt %), and high packing density, the PCS demonstrates a high C v (254 F cm–3), four times that of unassembled monodisperse carbon spheres. This work opens a new avenue to enhance the C v of porous carbons without compromising the rate capability or cyclability.
Efficient dual‐single‐atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction ...(HOR) in alkaline media and the facile dual‐single‐atom site generation remains formidable challenges. Here, we break the local symmetry of ultra‐small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1Ru1,n/rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen‐affine Co atom disrupts the symmetry of ultra‐small Ru nanoparticles, resulting in parasitic Ru and Co dual‐single‐atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2O. As anticipated, Co1Ru1,n/rGO exhibits ultrahigh mass activity (7.68 A mgRu−1) at 50 mV and exchange current density (0.68 mA cm−2), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi‐single‐atom and metal nanoparticle catalysis.
The symmetry of ultrasmall Ru nanoparticles is compromised by embedding Co single atoms, leading to the release of Ru single atoms and the formation of a Co1Ru1,n/rGO structure, which regulates the interaction between active sites and enhances the hydrogen oxidation reaction kinetics, mass activity and excellent durability.
Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total ...electrochemically active surface area (ECSA) for the oxygen reduction reaction (ORR) in hydrogen-based proton-exchange membrane fuel cells. Accordingly, a facile, low-cost, and hydrogen-assisted two-step method is developed in this work, to massively prepare carbon-supported uniform, small-sized, and surfactant-free Pd nanoparticles (NPs) with ultrathin ∼3-atomic-layer Pt shells (Pd@Pt
3L
NPs/C). Comprehensive physicochemical characterizations, electrochemical analyses, fuel cell tests, and density functional theory calculations reveal that, benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects, Pd@Pt
3L
NPs/C exhibits not only significantly enhanced ECSA, electrocatalytic activity, and noble-metal (NM) utilization compared to commercial Pt/C, showing 81.24 m
2
/g
Pt
, 0.710 mA/cm
2
, and 352/577 mA/mg
NM/Pt
in ECSA, area-, and NM-/Pt-mass-specific activity, respectively; but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test. More importantly, the corresponding 25-cm
2
H
2
-air/O
2
fuel cell with the low cathodic Pt loading of ∼ 0.152 mg
Pt
/cm
2
geo
achieves the high power density of 0.962/1.261 W/cm
2
geo
at the current density of only 1,600 mA/cm
2
geo
, which is much higher than that for the commercial Pt/C. This work not only develops a high-performance and practical Pt-based ORR electrocatalyst, but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure, which can be further expanded to other metal shells for other energy-conversion applications.
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