Designing earth-abundant electrocatalysts with high performance towards water oxidation is highly decisive for the sustainable energy technologies. This study develops a facile natural corrosion approach to fabricate nickel-iron hydroxides for water oxidation. The resulted electrode demonstrates an outstanding activity and stability with an overpotential of 275 mV to deliver 10 mA·cm−2. Experimental and theoretical results suggest the corrosion-induced formation of hydroxides and their transformation to oxyhydroxides would account for this excellent performance. This work not only provides an interesting corrosion approach for the fabrication of excellent water oxidation electrode, but also bridges traditional corrosion engineering and novel materials fabrication, which would offer some insights in the innovative principles for nanomaterials and energy technologies.
Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis, but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature. We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer (PtNi@Pt-SL) towards efficient triiodide reduction reaction (TRR) via an acid-dealloying approach. The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys, and thus results in good catalytic performance towards TRR. Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites. The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.
Potassium-ion batteries (PIBs) are appealing alternatives to conventional lithium-ion batteries (LIBs) because of their wide potential window, fast ionic conductivity in the electrolyte, and reduced cost. However, PIBs suffer from sluggish K+ reaction kinetics in electrode materials, large volume expansion of electroactive materials, and the unstable solid electrolyte interphase. Various strategies, especially in terms of electrode design, have been proposed to address these issues. In this review, the recent progress on advanced anode materials of PIBs is systematically discussed, ranging from the design principles, and nanoscale fabrication and engineering to the structure-performance relationship. Finally, the remaining limitations, potential solutions, and possible research directions for the development of PIBs towards practical applications are presented. This review will provide new insights into the lab development and real-world applications of PIBs.
Two-dimensional (2D) oxide can be continuously produced by bubbling oxygen into liquid metals and the harvesting of these oxide relies on the proper choice of dispersion solvents. The mass-production of ligand-free 2D materials from high melting-point metals will not be possible if the limited stability of the traditional dispersion solvents is not circumvented. Herein, liquid tin was used for the first time in the bubbling protocol and 2D tin oxide was obtained in molten salts. The nanosheets were studied with combined microscopic and spectroscopic techniques, and high-density grain boundaries was identified between the sub-5-nm nano-crystallites in the nanosheets. It gives rise to the high performance in electrocatalytic CO2 reduction reaction. Density-functional-theory based calculation was applied to achieve a deeper understanding of the relationship between the activity, selectivity, and the grain-boundary features. The molten-salt based protocol could be explored for the synthesis of a library of functional 2D oxides.
Tellurene, probably one of the most promising two-dimensional (2D) system in the thermoelectric materials, displays ultra-low thermal conductivity. However, a linear thickness-dependent thermal conductivity of unique tellurium nanoribbons in this study reveals that unprecedently low thermal conductivity can be achieved via well-defined nanostructures of low-dimensional tellurium instead of pursuing dimension-reduced 2D tellurene. For thinnest tellurium nanoribbon with thickness of 144 nm, the thermal conductivity is only ∼1.88 ± 0.22 W·m−1·K−1 at room temperature. It’s a dramatic decrease (45%), compared with the well-annealed high-purity bulk tellurium. To be more specific, an expected thermal conductivity of tellurium nanoribbons is even lower than that of 2D tellurene, as a result of strong phonon-surface scattering. We have faith in low-dimensional tellurium in which the thermoelectric performance could realize further breakthrough.
Despite the extensive application of porous nanostructures as oxygen electrocatalysts, it is challenging to synthesize single-metal state materials with porous structures, especially the ultrasmall ones due to the uniform diffusion of the same metal. Herein, we pioneer demonstrate a new size effect-based controllable synthesis strategy for the homogeneous Co nanokarstcaves assisted by Co-CN hybrids (CCHs). The preferential migration of cobalt atoms on the surface of small size zeolitic imidazolate framework (ZIF) with high surface energy during pyrolysis is the key factor for the formation of nanokarstcave structure. Furthermore, graphene can act as a diffusion barrier to prevent the agglomeration of nanoparticles in the synthesis process, which also plays an important role in the formation of porous nanostructures. In alkali media, CCHs achieve overpotential of 287 mV (@10 mA·cm−2) for oxygen evolution reaction (OER) and a half wave potential of 0.86 V (vs. RHE) for oxygen reduction reaction (ORR).
An efficient preparation and local coordination environment regulation of isolated single-atom sites catalysts (ISASC) for improved activity is still challenging. Herein, we develop a solid phase thermal diffusion strategy to synthesize Mn ISASC on highly uniform nitrogen-doped carbon nanotubes by employing MnO2 nanowires@ZIF-8 core-shell structure. Under high-temperature, the Mn species break free from core-MnO2 lattice, which will be trapped by carbon defects derived from shell-ZIF-8 carbonization, and immobilized within carbon substrate. Furthermore, the poly-dispersed Mn sites with two nitrogen-coordinated centers can be controllably renovated into four-nitrogen-coordinated Mn sites using NH3 treatment technology. Both experimental and computational investigations indicate that the symmetric coordinated Mn sites manifest outstanding oxygen reduction activity and superior stability in alkaline and acidic solutions. This work not only provides efficient way to regulate the coordination structure of ISASC to improve catalytic performance but also paves the way to reveal its significant promise for commercial application.
The rational design and construction of hierarchically porous nanostructure for oxygen reduction reaction (ORR) electrocatalysts is crucial to facilitate the exposure of accessible active sites and promote the mass/electron transfer under the gas-solid-liquid triple-phase condition. Herein, an ingenious method through the pyrolysis of creative polyvinylimidazole coordination with Zn/Fe salt precursors is developed to fabricate hierarchically porous Fe-N-doped carbon framework as efficient ORR electrocatalyst. The volatilization of Zn species combined with the nanoscale Kirkendall effect of Fe dopants during the pyrolysis build the hierarchical micro-, meso-, and macroporous nanostructure with a high specific surface area (1,586 m2·g−1), which provide sufficient exposed active sites and multiscale mass/charge transport channels. The optimized electrocatalyst exhibits superior ORR activity and robust stability in both alkaline and acidic electrolytes. The Zn-air battery fabricated by such attractive electrocatalyst as air cathode displays a higher peak power density than that of Pt/C-based Zn-air battery, suggesting the great potential of this electrocatalyst for Zn-air batteries.
Ferroelectric barium titanate nanoparticles (BTO NPs) may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors. While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade, the majority of the investigation was carried out in thin-film materials; therefore, the doping effect on nanoparticles remains unclear. Especially, doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled. In this work, we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), integrated differential phase contrast (iDPC)-STEM, and energy dispersive X-ray spectroscopy (EDX) mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles. Powder X-ray diffraction (PXRD) results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase, but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles. Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.
The development of rechargeable lithium-ion batteries (LIBs) is being driven by the ever-increasing demand for high energy density and excellent rate performance. Charge transfer kinetics and polarization theory, considered as basic principles for charge regulation in the LIBs, indicate that the rapid transfer of both electrons and ions is vital to the electrochemical reaction process. Graphene, a promising candidate for charge regulation in high-performance LIBs, has received extensive investigations due to its excellent carrier mobility, large specific surface area and structure tunability, etc. Recent progresses on the structural design and interfacial modification of graphene to regulate the charge transport in LIBs have been summarized. Besides, the structure-performance relationships between the structure of the graphene and its dedicated applications for LIBs have also been clarified in detail. Taking graphene as a typical example to explore the mechanism of charge regulation will outline ways to further understand and improve carbon-based nanomaterials towards the next generation of electrochemical energy storage devices.
Biochemical reactions in vivo occur at the temperature usually lower than that in vitro, however the underlying mechanism still remains a challenge. Inspired by our recent studies of adenosine triphosphate (ATP) releasing photons to resonantly drive DNA replication in a quantum way, we propose a quantized chemical reaction driven by multiple mid-infrared (MIR) photons. The space confinement effect of enzymes on a reactant molecule increases the lifetime of excitation state of its bond vibration, providing a chance for the bond to resonantly absorb multiple photons. Although the energy of each MIR photon is significantly lower than that of chemical bond, the resonant absorption of multiple photons can break the appointed bond of confined molecules. Different from the traditional thermochemistry and photochemistry, the quantized chemical reactions could have a high energy efficiency and ultrahigh selectivity. In addition, we also suggest a quantum driving source for our quantum-confined superfluid reactions proposed previously. The quantized chemical reaction resonantly driven by multiple MIR photons holds great promise to develop novel approaches for the chemical engineering in future.
Bifunctional electrocatalysts with high activity toward both oxygen reduction and evolution reaction are highly desirable for rechargeable Zn-air batteries. Herein, a kind of carbon nanotube (CNT) supported single-site Fe-N-C catalyst was fabricated via pyrolyzing in-situ grown Fe-containing zeolitic imidazolate frameworks on CNTs. CNTs not only serve as the physical supports of the Fe-N-C active sites but also provide a conductive network to facilitate the fast electron and ion transfer. The as-synthesized catalysts exhibit a half-wave potential of 0.865 V for oxygen reduction reaction and a low overpotential of 0.442 V at 10 mA·cm−2 for oxygen evolution, which is 310 mV smaller than that of Fe-N-C without CNTs. The rechargeable Zn-air batteries fabricated with such hybrid catalysts display a high peak power density of 182 mW·cm−2 and an excellent cycling stability of over 1,000 h at 10 mA·cm−2, which outperforms commercial Pt-C and most of the reported catalysts. This facile strategy of combining single-site Metal-N-C with CNTs network is effective for preparing highly active bifunctional electrocatalysts.
The depletion of energy and increasing environmental pressure have become one of the main challenges in the world today. Synthetic high-efficiency catalysts bring hope for efficient conversion of energy and effective treatment of pollutants, especially, single-atom catalysts (SACs) are promising candidates. Herein, we comprehensively summarizes the atomic diffusion strategy, which is considered as an effective method to prepare a series of SACs. According to the different diffusion forms of the precursors, we review the synthesis pathways of SACs from three aspects: gas diffusion, solid diffusion and liquid diffusion. The gaseous diffusion method mainly discusses atomic layer deposition (ALD) and chemical vapor deposition (CVD), both of which carry out gas phase mass transfer at high temperatures. The solid-state diffusion method can be divided into nanoparticle transformation into single atoms and solid atom migration. Liquid diffusion mainly describes the electrochemical method and the molten salt method. We hope this review can trigger the rational design of SACs.
Surfaces can significantly alter the optical properties of nanomaterials, but they are difficult to control and their roles are hard to understand in highly reactive materials such as silicon nanomaterials. In this work, we investigate the role of the surface in controlling the optical transitions in highly luminescent silicon-derived nanoparticles. By combining high-pressure and low-temperature experiments, we experimentally correlate the anomalously intense and narrow transitions in the UV range with the surface oxides, while the visible transition and the photoluminescence (PL) are verified to originate from the Si-ligand charge transfer band. We find that the high-pressure absorption and PL depends on the rigidity of the surface ligand. This indicates that the surface plays a dominant role on the optical properties of these silicon-derived nanoparticles, and is different than other semiconductor nanomaterials, in which pressure-dependent optical transitions depend on lattice strain or phase transformations. This work presents a comprehensive understanding of the optical transitions and the effect of surface ligands and surface oxidation in these highly luminescent Si-derived nanoparticles. The new insight into the oxidation-activated and ligand-mediated transitions, and the pressure-dependent PL may help with engineering the band structure of other highly-reactive optical nanomaterials.
The metal—organic frameworks (MOFs) are expected as ideal biomimetic enzymes for colorimetric glucose detection because of their large surface areas, well defined pore structures, tunable chemical composition, and multi-functional sites. However, the intrinsically chemical instability and low mimetic enzyme activity of MOFs hinder the application of them in imitating the enzyme reactions. In this work, we demonstrated a metal-MOF synergistic catalysis strategy, by loading Pt nanoparticles (Pt NPs) on MIL-88B-NH2 (Fe-MOF) to increase peroxidase-like activity for the detection of glucose. The induced electrons transfer from Pt atom to Fe atom accelerated the redox cycling of Fe3+/Fe2+, improved the overall efficiency of the peroxidase-like reaction, and enabled the efficient and robust colorimetric glucose detection, which was proved by both experiments and density functional theory (DFT) calculation. Additionally, the sensitivity and chemical stability of this synergistic effect strategy to detect the glucose are not affected by the complex external factors, which represented a great potential in fast, easy, sensitive, and specific recognition of clinical diabetes.
The rational fabrication of highly efficient electrocatalysts with low cost toward oxygen evolution reaction (OER) is greatly desired but remains a formidable challenge. In this work, we present a facile and straightforward method of incorporating NiCo-layered double hydroxide (NiCo-LDH) into GO-dispersed CNTs (GO-CNTs) with interconnected configuration. X-ray absorption spectroscopy (XAS) reveals the strong electron interaction between NiCo-LDH and the underlying GO-CNTs substrate, which is supposed to facilitate charge transfer and accelerate the kinetics for OER. By tuning the amount of CNTs, the optimized NiCo-LDH/GO-CNTs composite can achieve a low overpotential of 290 mV at 10 mA·cm−2 current density, a small Tafel slope of 66.8 mV·dec−1 and robust stability, superior to the pure NiCo-LDH and commercial RuO2 in alkaline media. The preeminent oxygen evolution performance is attributed to the synergistic effect stemming from the merits and the intimate electron interaction between LDH and GO-CNTs. This allows NiCo-LDH/GO-CNTs to be potentially applied in an industrial non-noble metal-based water electrolyzer as the anodic catalysts.
Lithium-sulfur (Li-S) battery has attracted intensive attention in the realm of energy storage owing to its high theoretical capacity and energy density. However, the shuttle effect of soluble lithium polysulfides (LiPSs) between electrodes results in rapid capacity degradation. Herein, a strategy which combines the design of both chemical interaction and microstructure of interlayer was proposed to suppress the shuttle effect. The chemical interaction between different functionalized MOFs and LiPSs was systematically studied to find the best candidate. Furthermore, an interlayer with ordered structure was constructed via the layer-by-layer assembly of metal-organic frameworks (MOFs) on graphene (UiO-66-NH2@graphene) to create sinuous channels which can better impede the diffusion process of LiPSs by the strong adsorption of MOF toward LiPSs. Consequently, in comparison to the battery with a bare separator, the ordered interlayer increased the initial discharge capacity of battery by 28.98% at 1.0 C and lowered the capacity decay rate remarkably from 0.10% to 0.067% per cycle, indicating that the design of chemical interaction and microstructure paves the way for high-performance Li-S batteries.