RESUMEN
Rational design hybrid nanostructure photocatalysts with efficient charge separation and transfer, and good solar light harvesting ability have critical significance for achieving high solar-to-chemical conversion efficiency. Here a highly active and stable composite photocatalyst is reported by integrating ultrathin ZnIn2 S4 nanosheets on surface of hollow CdS cube to form the cube-in-cube structure. Experimental results combined with density functional theory calculations confirm that the Z-scheme ZnIn2 S4 /CdS heterojunction is formed, which highly boosts the charge separation and transfer under the local-electric-field at semiconductor/semiconductor interface, and thus prolongs their lifetimes. Moreover, such a structure affords the highly enhanced light-harvesting property. The optimized ZnIn2 S4 /CdS nanohybrids exhibit superior H2 generation rate under visible-light irradiation (λ ≥ 420 nm) with excellent photochemical stability during 20 h continuous operation.
RESUMEN
Clarifying the responsibilities and constructing the synergy of different active phases are of great significance but still an urgent challenge for the heterostructure catalyst to improve the hydrogen evolution reaction (HER) process. Here, three-dimensional (3D) CoxNi(1-x)(OH)2 hollow structure integrating MoS2 nanosheet catalysts [CoxNi(1-x)(OH)2@MoS2] were ingeniously designed and prepared. This unique structure has realized the construction of a dual active phase for the optimized stepwise-synergetic hydrogen evolution process over a universal pH range through interface assembly engineering. Meanwhile, the 3D hollow heterostructure with a high surface-to-volume ratio can effectively avoid the agglomeration of MoS2 and enhance the CoxNi(1-x)(OH)2-MoS2 heterointerfaces. Thus, superior HER activity and stability were obtained over the universal pH range. Density functional theory calculation reveals that CoxNi(1-x)(OH)2 and MoS2 phases provide efficient active sites for rate-determining water dissociation and H* adsorption/H2 generation on CoxNi(1-x)(OH)2-MoS2 heterointerfaces, respectively, resulting in an optimized energy barrier for HER. This work proposes a constructive strategy to design highly efficient electrocatalysts based on the heterointerface with a defined responsible active phase of electrocatalysts.
RESUMEN
Although metallic chalcogenides are deemed as attractive sodium anode materials recently, the electrochemical performance is severely confined by the liability of structural collapse and sluggish ion diffusion kinetics. Herein a composite of carbon-encapsulated bimetallic selenides MoSe2-Sb2Se3 was prepared by a hydrothermal method on the basis of abundant reaction sites, high activity, an extra built-in electric field generated from heterointerfaces, and synergistic effects between the different components. Equally important, the carbon coating is effective to support the structural stability by restraining the vast volumetric variation to achieve the purpose of improving the cycling performance. The density functional theory calculation results indicate that the band gap is narrowed and that the work function is decreased on the interface of the MoSe2-Sb2Se3 heterojunction, leading to an additional driving force stemming from the introduction of the built-in electric field and the formation of the Sb-Se (Se from MoSe2) bond. Therefore, the resultant composite presents increased reaction kinetics and good electrochemical properties by acquiring a capacity of 376.0 mA h g-1 over 580 cycles at 2.0 A g-1 for the half-cell and 276 mA h g-1 over 750 cycles at 2 A g-1 for the full-cell. This work highlights bimetallic selenides with facilitated ion transferability with high performance.
RESUMEN
The design on synthesizing a sturdy, low-cost, clean, and sustainable electrocatalyst, as well as achieving high performance with low overpotential and good durability toward water splitting, is fairly vital in environmental and energy-related subject. Herein, for the first time the growth of sulfur (S) defect engineered self-supporting array electrode composed of metallic Re and ReS2 nanosheets on carbon cloth (referred as Re/ReS2 /CC) via a facile hydrothermal method and the following thermal treatment with H2 /N2 flow is reported. It is expected that, for example, the as-prepared Re/ReS2 -7H/CC for the electrocatalytic hydrogen evolution reaction (HER) under acidic medium affords a quite low overpotential of 42 mV to achieve a current density of 10 mA cm-2 and a very small Tafel slope of 36 mV decade-1 , which are comparable to some of the promising HER catalysts. Furthermore, in the two-electrode system, a small cell voltage of 1.30 V is recorded under alkaline condition. Characterizations and density functional theory results expound that the introduced S defects in Re/ReS2 -7H/CC can offer abundant active sites to advantageously capture electron, enhance the electron transport capacity, and weaken the adsorption free energy of H* at the active sites, being responsible for its superior electrocatalytic performance.
