Domain-Confined Multiple Collision Enhanced Catalytic Soot Combustion over a Fe₂O₃/TiO₂–Nanotube Array Catalyst Prepared by Light-Assisted Cyclic Magnetic Adsorption

The ordered TiO₂ nanotube array (NA)-supported ferric oxide nanoparticles with adjustable content and controllable particulate size were prepared through a facile light-assisted cyclic magnetic adsorption (LCMA) method. Multiple techniques such as SEM, TEM, EDX, XRD, EXAFS, XPS, UV–vis absorption, and TG were employed to study the structure and properties of the catalysts. The influencing factors upon soot combustion including the annealing temperature and loading of the active component in Fe₂O₃/TiO₂–NA were also investigated. An obvious confinement effect on the catalytic combustion of soot was observed for the ferric oxide nanoparticles anchored inside TiO₂ nanotubes. On the basis of the catalytic performance and characterization results, a novel domain-confined multiple collision enhanced soot combustion mechanism was proposed to account for the observed confinement effect. The design strategy for such nanotube array catalysts with domain-confined macroporous structure is meaningful and could be well-referenced for the development of other advanced soot combustion catalysts

Boosting Electrocatalytic Hydrogen-Evolving Activity of Co/CoO Heterostructured Nanosheets via Coupling Photogenerated Carriers with Photothermy

Electrocatalytic hydrogen evolution from water splitting holds great promise for renewable energy conversion and usage, but its application is limited by high energy consumption. The development of a facile strategy to efficiently improve the efficiency of energy conversion and the sluggish reaction kinetics using low-cost and stable electrocatalysts is crucial but still highly challenging. Recently, light irradiation is demonstrated to be an efficient external driving force for improving the hydrogen evolution reaction (HER) activities of electrocatalysts. The enhancement of activities arise from either light-excited hot electrons/carriers or photothermy, while the integrating of two action mechanisms is rarely reported. Herein, we present a synergetic effect between light-excited carriers and photothermy to enhance electrocatalytic HER activities of a Co/CoO heterostructured ultrathin nanosheet array supported on Ni foam (denoted as Co/CoO-NF). After exposure to light irradiation, the overpotential at 10 mA cm^–2 decreased from 232 mV (dark) to 140 mV (light), and the Tafel slope decreased from 151 mV dec^–1 (dark) to 85 mV dec^–1 (light) for Co/CoO-NF. The coupling effect between photogenerated carriers and photothermy is demonstrated for the improvement of electrocatalytic activities through a series of characterizations, revealing a new avenue for developing a novel electrocatalytic system with high efficiency of energy conversion

Photogenerated Carriers Boost Water Splitting Activity over Transition-Metal/Semiconducting Metal Oxide Bifunctional Electrocatalysts

The development of a facile and general strategy to simultaneously enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities of bifunctional electrocatalysts is of great importance for practical applications. However, current strategies are usually restricted to monofunctional electrocatalysts owing to the opposite redox process at cathode and anode. Herein, we present a photogenerated-carrier-driven strategy to enhance the electrocatalytic HER and OER activities of transition-metal/semiconductor bifunctional electrocatalysts. The Ni/NiO heterostructured ultrathin nanosheet array supported on Ni foam (denoted as Ni/NiO-NF) is chosen as the model metal/semiconductor bifunctional electrocatalyst and exhibits 10- and 2.6-fold enhancement of mass activity for HER and OER, respectively, after exposure to light irradiation. The increase in water-splitting activities can be attributed to the transfer of photogenerated electrons from excited NiO to HER-active Ni and the accelerating formation of OER-active Ni^III/IV, respectively

Engineering Sulfur Defects, Atomic Thickness, and Porous Structures into Cobalt Sulfide Nanosheets for Efficient Electrocatalytic Alkaline Hydrogen Evolution

The development of nonprecious metal-based electrocatalysts with high mass activity and efficient atom utilization for alkali hydrogen evolution reaction (HER) is of great importance for the preparation of hydrogen resource. The combination of ultrathin and porous structure, especially with the assistance of vacancy, is expected to be beneficial for achievement of high mass activity, but the development of a facile, robust, and generalized strategy to engineer ultrathin, porous, and vacancy-rich structure into nonlayer structured transition metal-based electrocatalysts is highly challenging. Here, we propose a plasma-induced dry exfoliation method to prepare nonlayer structured Co₃S₄ ultrathin porous nanosheets with abundant sulfur vacancies (Co₃S₄ PNS_vac), which show an onset overpotential of only 18 mV and an extremely large mass activity of 1056.6 A g^–1 at an overpotential of 200 mV. Experimental results and theoretical calculations confirm that the efficient alkaline HER performance could be attributed to the abundant active sites, good intrinsic activity, and accelerated electron/mass transfer. Additionally, the plasma-assisted conversion method can also be extended to fabricate CoSe₂ and NiSe₂ ultrathin porous nanosheets with selenium vacancies

Synthesis of Two-Dimensional CoS_1.097/Nitrogen-Doped Carbon Nanocomposites Using Metal–Organic Framework Nanosheets as Precursors for Supercapacitor Application

Two-dimensional (2D) metal–organic framework (MOF) nanosheets are attracting increasing research interest. Here, for the first time, we report the facile synthesis of 2D porphyrin paddlewheel framework-3 (PPF-3) MOF nanosheets with thickness of ca. 12–43 nm. Through the simultaneous sulfidation and carbonization of PPF-3 MOF nanosheets, we have prepared the 2D nanocomposite of CoS_1.097 nanoparticles (NPs) and nitrogen-doped carbon, referred to as CoSNC, in which the CoS_1.097 NPs with size of ca. 10 nm are embedded in the nitrogen-doped carbon matrix. As a proof-of-concept application, the obtained 2D CoSNC nanocomposite is used as an electrode material for a supercapacitor, which exhibits a specific capacitance of 360.1 F g^–1 at a current density of 1.5 A g^–1. Moreover, the composite electrode also shows high rate capability. Its specific capacitance delivered at a current density of 30.0 A g^–1 retains 56.8% of the value at 1.5 A g^–1

Edge Epitaxy of Two-Dimensional MoSe₂ and MoS₂ Nanosheets on One-Dimensional Nanowires

Rational design and synthesis of heterostructures based on transition metal dichalcogenides (TMDs) have attracted increasing interests because of their promising applications in electronics, catalysis, etc. However, the construction of epitaxial heterostructures with an interface at the edges of TMD nanosheets (NSs) still remains a great challenge. Here, we report a strategy for controlled synthesis of a new type of heterostructure in which TMD NSs, including MoS₂ and MoSe₂, vertically grow along the longitudinal direction of one-dimensional (1D) Cu_2–<i>x</i>S nanowires (NWs) in an epitaxial manner. The obtained Cu_2–<i>x</i>S-TMD heterostructures with tunable loading amount and lateral size of TMD NSs are achieved by the consecutive growth of TMD NSs on Cu_2–<i>x</i>S NWs through gradual injection of chalcogen precursors. After cation exchange of Cu in Cu_2–<i>x</i>S-TMD heterostructures with Cd, the obtained CdS–MoS₂ heterostructures retained their original architectures. Compared to the pure CdS NWs, the CdS–MoS₂ heterostructures with 7.7 wt % loading of MoS₂ NSs exhibit the best performance in the photocatalytic hydrogen evolution reaction with a H₂ production rate up to 4647 μmol·h^–1·g^–1, about 58 times that catalyzed with pure CdS NWs. Our synthetic strategy opens up a new way for the controlled synthesis of TMD-based heterostructures, which could have various promising applications