Developing cost-effective and sustainable catalysts with exceptional activity and selectivity is essential for the practical implementation of on-site H2O2 electrosynthesis, yet it remains a formidable challenge. Metal phosphide core-shell heterostructures anchored in carbon nanosheets (denoted as Ni@Ni2P/C NSs) are designed and synthesized via carbonization and phosphidation of the 2D Ni-BDC precursor. This core-shell nanostructure provides more accessible active sites and enhanced durability, while the 2D carbon nanosheet substrate prevents heterostructure aggregation and facilitates mass transfer. Theoretical calculations further reveal that the Ni/Ni2P heterostructure-induced optimization of geometric and electronic structures enables the favored adsorption of OOH* intermediate. All these features endow the Ni@Ni2P/C NSs with remarkable performance in 2e ORR for H2O2 synthesis, achieving a top yield rate of 95.6 mg L-1 h-1 with both selectivity and Faradaic efficiency exceeding 90% under a wide range of applied potentials. Furthermore, when utilized as the anode of an assembled gas diffusion electrode (GDE) device, the Ni@Ni2P/C NSs achieve in situ H2O2 production with excellent long-term durability (>32 h). Evidently, this work provides a unique insight into the origin of 2e ORR and proposes optimization of H2O2 production through nano-interface manipulation.
Recently, the development of new materials and devices has become the main research focus in the field of energy. Supercapacitors (SCs) have attracted significant attention due to their high power density, fast charge/discharge rate, and excellent cycling stability. With a lamellar structure, 2D transition metal dichalcogenides (2D TMDs) emerge as electrode materials for SCs. Although many 2D TMDs with excellent energy storage capability have been reported, further optimization of electrode materials and devices is still needed for competitive electrochemical performance. Previous reviews have focused on the performance of 2D TMDs as electrode materials in SCs, especially on their modification. Herein, the effects of element doping, morphology, structure and phase, composite, hybrid configuration, and electrolyte are emphatically discussed on the overall performance of 2D TMDs-based SCs from the perspective of device optimization. Finally, the opportunities and challenges of 2D TMDs-based SCs in the field are highlighted, and personal perspectives on methods and ideas for high-performance energy storage devices are provided.
Due to the limited reserves of metals, scientists are devoted to exploring high-performance metal-free catalysts based on carbon materials to solve environment-related issues. Doping would build up inhomogeneous charge distribution on surface, which is an efficient approach for boosting the catalytic performance. However, doping sites are difficult to control in traditional carbon materials, thus hindering their development. Taking the advantage of unique sp-C in graphdiyne (GDY), a new N doping configuration of sp-hybridized nitrogen (sp-N), bringing a Pt-comparable catalytic activity in oxygen reduction reaction is site-defined introduced. However, the reaction intermediate of this process is never captured, hindering the understanding of the mechanism and the precise synthesis of metal-free catalysts. After the four-year study, the fabrication of intermediate-like molecule is realized, and finally sp-N doped GDY via the pericyclic reaction is obtained. Compared with GDY doped with other N configurations, the designed sp-N GDY shows much higher catalytic activity in electroreduction of CO2 toward CH4 production, owing to the unique electronic structure introduced by sp-N, which is more favorable in stabilizing the intermediate. Thus, besides opening the black-box for the site-defined doping, this work reveals the relationship between doping configuration and products of CO2 reduction.
Hollow multishelled structure (HoMS) is a promising multi-functional platform for energy storage, owing to its unique temporal-spatial ordering property and buffering function. Accurate co-control of its multiscale structures may bring fascinating properties and new opportunities, which is highly desired yet rarely achieved due to the challenging synthesis. Herein, a sequential sulfidation and etching approach is developed to achieve the delicate co-control over both molecular- and nano-/micro-scale structure of WS2- x HoMS. Typically, sextuple-shelled WS2- x HoMS with abundant sulfur vacancies and expanded-interlayer spacing is obtained from triple-shelled WO3 HoMS. By further coating with nitrogen-doped carbon, WS2- x HoMS maintains a reversible capacity of 241.7 mAh g-1 at 5 A g-1 after 1000 cycles for sodium storage, which is superior to the previously reported results. Mechanism analyses reveal that HoMS provides good electrode-electrolyte contact and plentiful sodium storage sites as well as an effective buffer of the stress/strain during cycling; sulfur vacancy and expanded interlayer of WS2- x enhance ion diffusion kinetics; carbon coating improves the electron conductivity and benefits the structural stability. This finding offers prospects for realizing practical fast-charging, high-energy, and long-cycling sodium storage.
Because of its advantages such as abundant resources, low cost, simple synthesis, and high electrochemical stability, cobalt phosphide (CoP) is considered as a promising candidate for electrocatalytic hydrogen evolution reaction. Through element doping, the morphology and electronic structure of the catalyst can be tuned, resulting in both the increase of the active site number and the improvement of the intrinsic activity of each site. Herein, we designed and fabricated Mn-doped CoP nanowires with a length of 3 µm, a diameter of 50 nm, and the pores between the grains of 10 nm. As a highly efficient electrocatalyst for alkaline hydrogen evolution, the Mn10-doped CoP/NF (doping amount is about 10 atom %) electrode presented overpotentials of 60 mV @ 10 mA cm-2 and 112 mV @ 100 mA cm-2, improved by 35 and 23%, respectively, compared with CoP/NF. Characterizations indicate that Mn doping increases the electrochemical active area, reduces the impedance, and tunes the electronic structure of the material. Density functional theory calculations also revealed that an appropriate amount of Mn dopant at a suitable location can both react as an active site itself and boost the activity of the surrounding Co sites, delivering favorable H* adsorption and rapid reaction kinetics. This result may not only promote the development of hydrogen evolution reaction catalysts but also encourage explorations of the relationship between the property and fine doping structure.
The coupling of TiO2 and SrTiO3 through elaborate bandgap engineering can provide synergies for highly efficient photocatalysts. To further improve the separation between photogenerated electrons and holes, a nano-heterostructured combination of semicrystalline SrTiO3 (S-SrTiO3 ) and anatase TiO2 nanoparticles is designed, and an optimized interface is achieved between uniformly grown S-SrTiO3 and metal organic framework (MOF)-derived anatase TiO2 through a controlled hydrothermal process. Besides tuning of the bandgap and broadening of the absorption spectral range, S-SrTiO3 particles alleviate charge carrier recombination benefiting from the coupling of the semicrystalline SrTiO3 around the interface. Additionally, highly dispersed S-SrTiO3 on TiO2 provides a good spatial distribution of active sites and the abundant carbon remained from MOF may reduce charge transport resistance. Moreover, the rapid transfer within the nano-heterostructure promotes the separation of the photogenerated charge carriers. With the above predominant architecture, when used as a photocatalyst, the as-synthesized S-SrTiO3 /TiO2 heterostructure exhibits exceptionally high photocatalytic performance of 13â¯005 µmol h-1 g-1 for H2 production, exceeding most oxide-based photocatalysts reported. This study might provide mechanistic insights into a new perspective for the design and preparation of photocatalysts with novel structure and enhanced catalysis activity.
Solar evaporation, which enables water purification without consuming fossil fuels, has been considered the most promising strategy to address global scarcity of drinkable water. However, the suboptimal structure and composition designs still result in a trade-off between photothermal conversion, water transport, and tolerance to harsh environments. Here, an ultrastable amorphous Ta2 O5 /C nanocomposite is designed with a hollow multishelled structure (HoMS) for solar evaporation. This HoMS results in highly efficient photoabsorption and photothermal conversion, as well as a decrease of the actual water evaporation enthalpy. A superfast evaporation speed of 4.02 kg m-2 h-1 is achieved. More importantly, a World Health Organization standard drinkable water can be achieved from seawater, heavy-metal- and bacteria-containing water, and even from extremely acidic/alkaline or radioactive water sources. Notably, the concentration of pseudovirus SC2-P can be decreased by 6 orders of magnitude after evaporation.
Achieving highly efficient hydrogen evolution reaction (HER) in alkaline media is a great challenge. Single-atom catalysts with high-loading amount have attracted great interest due to their remarkable catalytic properties. Herein, by using nickel foam as the substrate, the authors design and precisely synthesize atomic ruthenium (Ru)-loaded nickel hydroxide ultrathin nanoribbons (R-NiRu) with a high atomic Ru loading amount reaching ≈7.7 wt% via a one-step hydrothermal method. The presence of concentrated Cl- in the synthetic system is beneficial for constructing ultrathin nanoribbons, which, with abundant edge OH groups, make it easy to trap atomic Ru. Taking advantage of the synergy between atomic Ru and the nanoribbon morphology of nickel hydroxide, R-NiRu exhibit a low overpotential of 16 mV for HER at 10 mA cm-2 and a Tafel slope of 40 mV dec-1 in aqueous 1.0 m KOH solution, which are superior to those of commercial Pt/C (overpotential of 17 mV at 10 mA cm-2 , Tafel slope of 43 mV dec-1 ). Density functional theory (DFT) calculation results demonstrate that atomically dispersed Ru can significantly reduce the HER energy barrier. Moreover, R-NiRu maintains exceptional stability after 5000 cyclic voltammetry cycles. This efficient and facile synthetic strategy provides a new avenue for designing efficient catalysts.
La- and Rh-co-doped SrTiO3 (STO:La/Rh) hollow multishelled structures (HoMSs) are fabricated by adding La3+ and Rh3+ ions during the hydrothermal process of converting TiO2 HoMSs to STO HoMSs. STO:La/Rh HoMSs have successfully expanded the light absorption edge to 520 nm. Accompanied with the benefits of the unique hierarchical structure and relatively thin shells, STO:La/Rh HoMSs exhibit elevated light-harvesting capacity and charge separation efficiency. Compared with STO:La/Rh nanoparticles (NPs), STO:La/Rh HoMSs demonstrate enhanced photocurrent response, photocatalytic hydrogen evolution activity, and the quantum efficiency. Moreover, overall water splitting is realized by a Z-scheme system combining STO:La/Rh HoMSs with BiVO4 (BVO) nanosheets with 1 wt% Pt as the co-catalyst. Steady evolution of hydrogen and oxygen is performed under both visible light and simulated sunlight irradiation. The solar-to-hydrogen efficiency of double-shelled STO:La/Rh HoMS-BVO photocatalysts reaches 0.08%, which is twofold higher than STO:La/Rh NP-BVO photocatalysts.
Hollow multishelled structures (HoMSs) provide a promising platform for fabricating photocatalysts, because the unique structure optimizes the effective surface and mass transport, showing enhanced light absorption, optimized mass transport and highly effective active sites exposed. Subsequently, the rational design on HoMS photocatalytsts is elaborated to boost the photocatalytic activity with efforts in all dimensions, from nanoscale to microscale. Breakthroughs in synthetic methodology of HoMSs have greatly evoked the prosperous photocatalytic researches for HoMSs since the developing of sequential templating approach in 2009. The dawn of HoMS photocatalyst is coming after revealing the temporal-spatial ordering property, which is also discussed in this paper with pioneer works demonstrating the greatly enhanced energy/mass transfer processes. Some insights into the key challenges and perspectives of HoMSs photocatalysts are also discussed. With the reviewed fate and future of HoMSs photocatalysts, hopefully new concepts and innovative works can be inspired to flourish this sun-rise field.
To boost the performance for various applications, a rational bottom-up design on materials is necessary. The defect engineering on nanoparticle at the atomic level can efficiently tune the electronic behavior, which offers great opportunities in enhancing the catalytic performance. In this paper, we optimized the surface oxygen vacancy concentration and created the lattice distortion in rare-earth-based perovskite oxide through gradient replacement of the Bâ site with valence alternated element. The dual defects make the electron spin state transit from low spin state to high spin state, thus decreasing the charge transport resistance. Furthermore, assembly the modified nanoparticle subunits into the micro-sized hollow multishelled structures can provide porous shells, abundant interior space and effective contact, which enables an enhanced mass transfer and a shorter charge transport path. As a result, the systemic design in the electronic and nano-micro structures for catalyst has brought an excellent oxygen evolution performance.
Textile-based energy-storage devices are highly appealing for flexible and wearable electronics. Here, a 3D textile cathode with high loading, which couples hollow multishelled structures (HoMSs) with conductive metallic fabric, is reported for high-performance flexible lithium-ion batteries. V2 O5 HoMSs prepared by sequential templating approach are used as active materials and conductive metallic fabrics are applied as current collectors and flexible substrates. Taking advantage of the desirable structure of V2 O5 HoMSs that effectively buffers the volume expansion and alleviates the stress/strain during repeated Li-insertion/extraction processes, as well as the robust flexible metallic-fabric current collector, the as-prepared fabric devices show excellent electrochemical performance and ultrahigh stability. The capacity retains a high value of 222.4 mA h g-1 at a high mass loading of 2.5 mg cm-2 even after 500 charge/discharge cycles, and no obvious performance degradation is observed after hundreds of cycles of bending and folding. These results indicate that V2 O5 HoMSs/metallic-fabric cathode electrode is promising for highly flexible lithium-ion batteries.
The lithium-ion capacitor (LIC) has attracted tremendous research interest because it meets both the requirement on high energy and power densities. The balance between effective surface areas and mass transport is highly desired to fabricate the optimized electrode material for LIC. Now, triple-shelled (3S) Nb2 O5 hollow multi-shelled structures (HoMSs) were synthesized for the first time through the sequential templating approach and then applied for the anode of LIC. The unique structure of HoMSs, such as large efficient surface area, hierarchical pores, and multiple shells, provides abundant reaction sites, decreases the electron transport resistance, and increases the diffusion rate for ion transport. In this case, the best combination performance has been achieved among all the reported Nb2 O5 -based materials, which delivered an excellent energy and power densities simultaneously, and superb cycling stability.
In nature, sequential harvesting of light widely exists in the old life entity, i.e. cyanobacteria, to maximize the light absorption and enhance the photosynthesis efficiency. Inspired by nature, we propose a brand new concept of temporally-spatially sequential harvesting of light in one single particle, which has purpose-designed heterogeneous hollow multi-shelled structures (HoMSs) with porous shells composed of nanoparticle subunits. Structurally, HoMSs consist of different band-gap materials outside-in, thus realizing the efficient harvesting of light with different wavelengths. Moreover, introducing oxygen vacancies into each nanoparticle subunit can also enhance the light absorption. With the benefit of sequential harvesting of light in HoMSs, the quantum efficiency at wavelength of 400 nm is enhanced by six times compared with the corresponding nanoparticles. Impressively, using these aforementioned materials as photocatalysts, highly efficient photocatalytic water splitting is realized, which cannot be achieved by using the nanoparticle counterparts. This new concept of temporally-spatially sequential harvesting of solar light paves the way for solving the ever-growing energy demand.
The crystal phase plays an important role in controlling the properties of a nanomaterial; however, it is a great challenge to obtain a nanomaterial with high purity of the metastable phase. For instance, the large-scale synthesis of the metallic phase MoS2 (1T-MoS2 ) is important for enhancing electrocatalytic reaction, but it can only be obtained under harsh conditions. Herein, a spatially confined template method is proposed to synthesize high phase-purity MoS2 with a 1T content of 83 %. Moreover, both the confined space and the structure of template will affect the purity of 1T-MoS2 ; in this case, this approach was extended to other similar spatially confined templates to obtain the high-purity material. The obtained ultrathin nanosheets exhibit good electrocatalytic activity and excellent stability in the hydrogen evolution reaction.
Herein, we present heterogeneous hollow multi-shelled structures (HoMSs) prepared by exploiting the properties of the metal-organic framework (MOFs) casing. Through accurately controlling the transformation of MOF layer into different heterogeneous casings, we can precisely design HoMSs of SnO2 @Fe2 O3 (MOF) and SnO2 @FeOx -C(MOF), which not only retain properties of the original SnO2 -HoMSs, but also structural information from the MOFs. Tested as anode materials in LIBs, SnO2 @Fe2 O3 (MOF)-HoMSs demonstrate superior lithium-storage capacity and cycling stability to the original SnO2 -HoMSs, which can be attributed to the topological features from the MOF casing. Making a sharp contrast to the electrodes of SnO2 @Fe2 O3 (particle)-HoMSs fabricated by hydrothermal method, the capacity retention after 100â cycles for the SnO2 @Fe2 O3 (MOF)-HoMSs is about eight times higher than that of the SnO2 @Fe2 O3 (particle)-HoMS.
Lanthanide-doped nanomaterials have attracted significant attention for their preeminent properties and widespread applications. Due to the unique characteristic, the lanthanide-doped photoluminescence materials with hollow structures may provide advantages including enhanced light harvesting, intensified electric field density, improved luminescent property, and larger drug loading capacity. Herein, the synthesis, properties, and applications of lanthanide-doped photoluminescence hollow structures (LPHSs) are comprehensively reviewed. First, different strategies for the engineered synthesis of LPHSs are described in detail, which contain hard, soft, self-templating methods and other techniques. Thereafter, the relationship between their structure features and photoluminescence properties is discussed. Then, niche applications including biomedicines, bioimaging, therapy, and energy storage/conversion are focused on and superiorities of LPHSs for these applications are particularly highlighted. Finally, keen insights into the challenges and personal prospects for the future development of the LPHSs are provided.
Lanthanoid Series Elements/chemistry , Luminescence , Electricity , Lanthanoid Series Elements/chemical synthesis , Nanospheres/ultrastructure
TiO2 is a potential anode material for lithium-ion batteries due to its high rate capability and high safety. Here, a controllable synthesis for hollow nanostructured TiO2 , with heterostructured shells of TiO2 (B) and anatase phases, is presented for the first time, by using a sequential templating approach. The hollow nanostructures can be easily controlled to produce core-shell and double-shelled materials with different compositional ratios of anatase to TiO2 (B) by tuning the synthetic conditions. When used as the anode materials for lithium-ion batteries, a specific discharge capacity of 215.4 mAh g-1 for the double-shelled anatase/TiO2 (B) hollow microspheres is achieved at a current rate of 1 C (335 mA g-1 ) for the 100th cycle and shows high specific discharge capacities of 141.6 and 125.7 mAh g-1 at the high rates of 10 and 20 C over 1000 cycles. These results are due to the unique stable hollow multishelled structure, which has a high specific surface area, as well as the interface between the heterostructured anatase/TiO2 (B) phases contributing a substantial number of lithium-ion storage sites.
Hollow micro/nanostructured CeO2 -based materials (HMNCMs) have triggered intensive attention as a result of their unique structural traits, which arise from their hollowness and the fascinating physicochemical properties of CeO2 . This attention has led to widespread applications with improved performance. Herein, a comprehensive overview of methodologies applied for the synthesis of various hollow structures, such as hollow spheres, nanotubes, nanoboxes, and multishelled hollow spheres, is provided. The synthetic strategies toward CeO2 hollow structures are classified into three major categories: 1) well-established template-assisted (hard-, soft-, and in situ template) methods; 2) newly emerging self-template approaches, including selective etching, Ostwald ripening, the Kirkendall effect, galvanic replacement, etc.; 3) bottom-up self-organized formation synthesis (namely, oriented attachment and self-deformation). Their underlying mechanisms are concisely described and discussed in detail, the differences and similarities of which are compared transversely and longitudinally. Niche applications of HMNCMs in a wide range of fields including catalysis, energy conversion and storage, sensors, absorbents, photoluminescence, and biomedicines are reviewed. Finally, an outlook of future opportunities and challenges in the synthesis and application of CeO2 -based hollow structures is also presented.
Precisely carving of multi-shelled manganese-cobalt oxide hollow dodecahedra (Co/Mn-HD) with shell number up to three is achieved by a controlled calcination of the Mn-doped zeolitic imidazolate framework ZIF-67 precursor (Co/Mn-ZIF). The unique multi-shelled and polycrystalline structure not only provides a very large electrochemically active surface area (EASA), but also enhances the structural stability of the material. The residual C and N in the final structures might aid stability and increase their conductivity. When used in alkaline rechargeable battery, the triple-shelled Co/Mn-HD exhibits high electrochemical performance, reversible capacity (331.94â mAh g-1 at 1â Ag-1 ), rate performance (88 % of the capacity can be retained with a 20-fold increase in current density), and cycling stability (96 % retention over 2000â cycles).
