Hierarchical FeCoS2–CoS2 double‐shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO2 reduction under visible light. The synthetic strategy, engaging the ...two‐step cation‐exchange reactions, precisely integrates two metal sulfides into a double‐shelled tubular heterostructure with both of the shells assembled from ultrathin two‐dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS2–CoS2 hybrid can reduce bulk‐to‐surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO2 adsorption and surface‐dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS2–CoS2 double‐shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO2 reduction, affording a high CO‐generating rate of 28.1 μmol h−1 (per 0.5 mg of catalyst).
The unique structure of hierarchical FeCoS2–CoS2 double‐shelled nanotubes constructed by ultrathin nanosheets can sufficiently inhibit recombination of electrons and holes by shortening diffusion length, exploit incident visible light by enhancing scattering in the cavity, and expose abundant active sites for redox reactions. Benefiting from these advantages, the obtained FeCoS2–CoS2 hybrid exhibits outstanding performance for CO2‐to‐CO conversion powered by solar light.
Ultrathin ZnIn2S4 nanosheets (NSs) are grown on Co/N‐doped graphitic carbon (NGC) nanocages, composed of Co nanoparticles surrounded by few‐layered NGC, to obtain hierarchical Co/NGC@ZnIn2S4 hollow ...heterostructures for photocatalytic H2 generation with visible light. The photoredox functions of discrete Co, conductive NGC, and ZnIn2S4 NSs are precisely combined into hierarchical composite cages possessing strongly hybridized shell and ultrathin layered substructures. Such structural and compositional virtues can expedite charge separation and mobility, offer large surface area and abundant reactive sites for water photosplitting. The Co/NGC@ZnIn2S4 photocatalyst exhibits outstanding H2 evolution activity (e.g., 11270 µmol h−1 g−1) and high stability without engaging any cocatalyst.
Hierarchical Co/N‐doped graphitic carbon (NGC)@ ZnIn2S4 heterostructured cages are fabricated by supporting ultrathin ZnIn2S4 nanosheets on Co/NGC nanocages. This delicate design can facilitate charge separation and transport as well as provide large surface area and rich active sites for water photosplitting reactions. Outstanding activity and high stability for H2 evolution under visible light are achieved without the assistance of any cocatalysts.
Prussian blue analogs (PBAs) are considered as reliable and promising cathode materials for aqueous Zn‐ion batteries (AZIBs), but they suffer from low capacity and poor cycling stability due to ...insufficient active sites and structural damage caused by the ion insertion/extraction processes. Herein, a template‐engaged ion exchange approach has been developed for the synthesis of Co‐substituted Mn‐rich PBA hollow spheres (CoMn‐PBA HSs) as cathode materials for AZIBs. Benefiting from the multiple advantageous features including hollow structure, abundant active sites, fast Zn2+ ion diffusion, and partial Co substitution, the CoMn‐PBA HSs electrode shows efficient zinc ion storage properties in terms of high capacity, decent rate capability and prolonged cycle life.
Co‐substituted Mn‐rich Prussian Blue Analog (PBA) hollow spheres (CoMn‐PBA HSs) are rationally designed and synthesized through an efficient self‐templating approach. Benefiting from the hollow structure and partial Co substitution, the CoMn‐PBA HSs electrode exhibits enhanced zinc ion storage performance with high capacity, favorable rate capability, and impressive cycling stability.
Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal‐organic framework‐assisted pyrolysis‐replacement‐reorganization approach ...is developed to obtain ultrafine Pt‐Co alloy nanoparticles (sub‐10 nm) attached on the inner and outer shells of porous nitrogen‐doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt‐Co nano‐alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically‐neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media.
Ultrafine Pt‐Co alloy nanoparticles confined on the inner and outer surfaces of porous nitrogen‐doped carbon nanotubes (Pt‐Co@NCNT) have been synthesized through a metal–organic framework (MOF)‐assisted pyrolysis‐replacement‐reorganization approach. With the structural and compositional merits, the Pt3Co@NCNT electrocatalyst presents superior activity and stability in both acidic and alkaline media for the hydrogen evolution reaction.
Electrocatalysts based on hierarchically structured and heteroatom‐doped non‐noble metal oxide materials are of great importance for efficient and low‐cost electrochemical water splitting systems. ...Herein, the synthesis of a series of hierarchical hollow nanoplates (NPs) composed of ultrathin Co3O4 nanosheets doped with 13 different metal atoms is reported. The synthesis involves a cooperative etching−coordination−reorganization approach starting from zeolitic imidazolate framework‐67 (ZIF‐67) NPs. First, metal atom decorated ZIF‐67 NPs with unique cross‐channels are formed through a Lewis acid etching and metal species coordination process. Afterward, the composite NPs are converted to hollow Co3O4 hierarchical NPs composed of ultrathin nanosheets through a solvothermal reaction, during which the guest metal species is doped into the octahedral sites of Co3O4. Density functional theory calculations suggest that doping of small amount of Fe atoms near the surface of Co3O4 can greatly enhance the electrocatalytic activity toward the oxygen evolution reaction (OER). Benefiting from the structural and compositional advantages, the obtained Fe‐doped Co3O4 hierarchical NPs manifest superior electrocatalytic performance for OER with an overpotential of 262 mV at 10 mA cm−2, a Tafel slope of 43 mV dec−1, and excellent stability even at a high current density of 100 mA cm−2 for 50 h.
Metal‐atom‐doped Co3O4 hierarchical nanoplates constructed by ultrathin nanosheets are synthesized by a cooperative etching−coordination−reorganization approach. The method allows doping of 13 metal elements in total. With its structural and compositional advantages, as an example, the Fe‐doped Co3O4 hierarchical nanoplates exhibit greatly enhanced electrocatalytic performance for oxygen evolution.
Metal–organic framework (MOF) composites have recently been considered as promising precursors to derive advanced metal/carbon‐based materials for various energy‐related applications. Here, a ...dual‐MOF‐assisted pyrolysis approach is developed to synthesize Co–Fe alloy@N‐doped carbon hollow spheres. Novel core–shell architectures consisting of polystyrene cores and Co‐based MOF composite shells encapsulated with discrete Fe‐based MOF nanocrystallites are first synthesized, followed by a thermal treatment to prepare hollow composite materials composed of Co–Fe alloy nanoparticles homogeneously distributed in porous N‐doped carbon nanoshells. Benefitting from the unique structure and composition, the as‐derived Co–Fe alloy@N‐doped carbon hollow spheres exhibit enhanced electrocatalytic performance for oxygen reduction reaction. The present approach expands the toolbox for design and preparation of advanced MOF‐derived functional materials for diverse applications.
A dual‐metal–organic framework pyrolysis approach is developed to synthesize cobalt–iron alloy/nitrogen‐doped carbon hollow spheres. With the structural and compositional advantages, these unique bimetallic alloy/carbon‐based materials exhibit enhanced electrocatalytic performance for oxygen reduction reaction.
The development of efficient and low‐cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage ...devices. Here, we report an elaborate design and synthesis of porous Co‐based trimetallic spinel oxide nanoboxes (NiCo2−xFexO4 NBs) by a novel metal‐organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo2−xFexO4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm−2, a small Tafel slope of 42 mV dec−1, and good stability in alkaline electrolyte, which is much better than that of Co‐based bi/monometallic spinel oxides and even commercial RuO2.
Co‐based trimetallic spinel oxide nanoboxes are synthesized through an elaborate strategy involving chemical etching, cation exchange and thermal oxidation processes. The unique structural and compositional advantages endow the trimetallic NiCo2−xFexO4 nanoboxes with superior electrocatalytic activity and stability toward oxygen evolution reaction.
The rational design of catalysts’ spatial structure is vitally important to boost catalytic performance through exposing the active sites, enhancing the mass transfer, and confining the reactants. ...Herein, a dual‐linker zeolitic tetrazolate framework‐engaged strategy is developed to construct assembled hollow plates (AHP) of N‐rich carbon (NC), which is loaded with single‐Ni atoms to form a highly efficient electrocatalyst (designated as Ni‐NC(AHP)). In the carbonization process, the thermally unstable linker (5‐aminotetrazole) serves as the self‐sacrificial template and the other linker (2‐methylimidazole) mainly serves as the carbon and nitrogen source to form hollow NC matrix. The formed Ni‐NC(AHP) catalyst possesses enhanced mesoporosity and more available surface area, thus promoting mass transport and affording abundant accessible single‐Ni sites. These features contribute to remarkable performance for electrochemical CO2 reduction with exceptionally high selectivity of nearly 100% towards CO in a wide potential range and dramatically enhanced CO partial current density.
Assembled hollow N‐rich carbon plates with single‐Ni atoms (Ni‐NC(AHP)) are constructed using a novel dual‐linker zeolitic tetrazolate framework (ZTF) as precursor. The open structure and high external surface area enable the Ni‐NC(AHP) catalyst with fast mass transfer and highly exposed single‐Ni sites towards efficient CO2 electroreduction.
Exploring earth‐abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi2S4 yolk‐shell ...spheres (P‐CoNi2S4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas‐phase phosphorization strategy. Benefiting from the strengthened Ni3+/Ni2+ couple, enhanced electronic conductivity, and hollow structure, the P‐CoNi2S4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of −0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm−2, respectively. Remarkably, when used as the anode and cathode simultaneously, the P‐CoNi2S4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm−2 with excellent durability for 100 h, outperforming most of the reported nickel‐based sulfides and even noble‐metal‐based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea‐rich wastewater treatment.
Phosphorus‐substituted CoNi2S4 yolk‐shell spheres (P‐CoNi2S4 YSSs) have been rationally designed and synthesized by a facile hydrothermal sulfidation and subsequent gas‐phase phosphorization strategy. The desired hollow structure and multielement composition with abundant Ni3+ active sites endow P‐CoNi2S4 YSSs with high electrocatalytic activity and robust stability towards electrochemical hydrogen production via water splitting and urea electrolysis.
Herein we report a simple dual‐soft‐template approach to prepare walnut‐shaped macro‐/mesoporous polydopamine particles with diameter of ca. 270 nm, highly accessible bicontinuous channels and wide ...pore size distribution from ca. 20 nm to ca. 95 nm. This approach provides great opportunities to tailor the soft template‐directed assembly processes and generate various polydopamine particles with controllable mesophase curvature. Walnut‐shaped mesoporous carbon particles with large open mesochannels in the range of ca. 13 nm to ca. 50 nm can be fabricated by subsequent thermal treatment under nitrogen atmosphere. Lastly, we demonstrate that the as‐derived walnut‐shaped carbon particles manifest enhanced electrocatalytic performance for oxygen reduction reaction in alkaline electrolyte.
Hole nuts: Novel walnut‐shaped macro‐/mesoporous particles are prepared through a dual‐soft‐template strategy. This approach provides great opportunities to tailor the polymer‐directed assembly processes and generate various polydopamine particles with controllable mesophase curvature. Their dervied carbon particles can be used in the oxygen reduction reaction.
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