Junxue Liu

Plasmonic enhancement of photocatalysis over Ag incorporated AgI hollow nanostructures

Hollow-structured polyhedral nanostructures of AgI nanoboxes and cube-tetrapod Ag/AgI cages have been fabricated through the controlled reaction of I− ions with nanocubes and cube-tetrapods of AgCl based on the principle of the Kirkendall effect. The Ag0 nanodomains in the source nanoparticles of AgCl:Ag are preserved in the final hollow Ag/AgI cages during the chemical conversion of AgCl to AgI. The obtained hollow cube-tetrapod Ag/AgI nanostructures exhibited enhanced light absorption in the visible region and photocatalytic performance towards hydrogen evolution from water reduction and decomposition of organic pollutants, owing to the contribution of the surface plasmon resonance (SPR) effect of silver nanoparticles (nanodomains). The present versatile route can be generalized to the preparation of other inorganic functional materials with hollow interiors for different applications.

Graphene oxide coupled AgBr nanosheets: an efficient dual-functional visible-light-responsive nanophotocatalyst with enhanced performance

A facile 2-dimensional coupling of AgBr nanosheets with graphene oxide (GO) sheet has been developed to fabricate an efficient dual-functional visible-light-responsive GO@AgBr nanophotocatalyst. Compared to bare AgBr nanosheets, the as-obtained GO@AgBr nanocomposite exhibits enhanced photocatalytic activity towards degradation of rhodamine-B (RhB) and evolution of H2 from aqueous-methanol solution. The RhB molecules can be decomposed completely within 4 min under visible light irradiation and the catalyst can be reused 10 times without losing activity. A possible mechanism for the highly efficient photocatalyst is proposed, implying GO serves as electron acceptor to facilitate the charge transfer and suppress the recombination of electron–hole pairs. This work provides a convenient means for the exploration of highly efficient and stable GO-based composite photocatalysts.

Ultrathin Co（Ni）-doped MoS2 nanosheets as catalytic promoters enabling efficient solar hydrogen production

The design of efficient artificial photosynthetic systems that harvest solar energy to drive the hydrogen evolution reaction via water reduction is of great importance from both the theoretical and practical viewpoints. Integrating appropriate co-catalyst promoters with strong light absorbing materials represents an ideal strategy to enhance the conversion efficiency of solar energy in hydrogen production. Herein, we report, for the first time, the synthesis of a class of unique hybrid structures consisting of ultrathin Co(Ni)-doped MoS2 nanosheets (co-catalyst promoter) intimately grown on semiconductor CdS nanorods (light absorber). The as-synthesized one-dimensional CdS@doped-MoS2 heterostructures exhibited very high photocatalytic activity (with a quantum yield of 17.3%) and stability towards H2 evolution from the photoreduction of water. Theoretical calculations revealed that Ni doping can increase the number of uncoordinated atoms at the edge sites of MoS2 nanosheets to promote electron transfer across the CdS/MoS2 interfaces as well as hydrogen reduction, leading to an efficient H2 evolution reaction.

Synthesis of few-layer 1T′-MoTe2 ultrathin nanosheets for high-performance pseudocapacitors

The synthesis of layered transition metal dichalcogenide nanocrystals with excellent properties in energy conversion and storage has been well documented in the past several years. However, due to the metallic character of Te, the realization of the chemical synthesis of uniform well-defined MoTe2 nanostructures still remains a challenge, especially to achieve metastable 1T′-MoTe2. In this work, we have developed a colloidal chemical strategy for the synthesis of ultrathin 1T′-MoTe2 nanosheets. The as-achieved sample was characterized by a layered-expanded feature with an interlayer distance of 0.723 nm and rich defects. The shapes of 1T′-MoTe2 can be controlled by varying Mo precursors and the reaction atmosphere, where CO plays an essential role in determining the nanosheet feature. Interestingly, the optimized few-layer 1T′-MoTe2 nanosheets can be used as an efficient supercapacitor electrode with specific capacitances of 1393 F g−1 and 714 F g−1 at current densities of 1 A g−1 and 100 A g−1, respectively. An asymmetric 1T′-MoTe2//activated carbon supercapacitor exhibits a maximum specific capacitance of 158.9 F g−1 with an energy density up to 56.4 W h kg−1. To the best of our knowledge, it is the first time that ultrathin MoTe2 nanosheets have been used as ideal electrode materials for supercapacitors. The present work highlights a facile synthetic strategy to realize uniform transition metal telluride nanostructures for enhancing their electrochemical performances.

Hollow AgI:Ag Nanoframes as Solar Photocatalysts for Hydrogen Generation from Water Reduction

A facile strategy based on the principle of the Kirkendall effect has been developed to synthesize hollow nanoframes and nanoshells of AgI:Ag composites through the controlled anion-exchange reaction between I(-) ions and solid AgBr:Ag (or AgCl:Ag) nanoparticles that serve as templates. Regardless of the morphologies of the template nanoparticles, they can be chemically transformed to hollow AgI:Ag structures with morphologies similar to those of the templates. The synthesized hollow AgI:Ag nanostructures can be used as efficient photocatalysts for H2 generation from water reduction and the decomposition of organic pollutants owing to the enhanced absorption of visible light by the Ag components in the hybrid nanostructures. The hollow nanostructures exhibit a higher photocatalytic performance than the corresponding solid nanoparticles possibly because of the large surface area and unique AgI/Ag interfaces associated with the hollow nanostructures.

Silver Iodide Nanospheres Wrapped in Reduced Graphene Oxide for Enhanced Photocatalysis

We have prepared nanocomposites of well‐defined spherical AgI nanostructures wrapped in reduced graphene oxide nanosheets (AgI@RGO). The as‐obtained AgI@RGO nanocomposites exhibit an enhanced photocatalytic activity and stability in the degradation of organic pollutants, namely, Rhodamine B (RhB), in comparison with bare AgI nanospheres. The hybridization of AgI nanospheres with RGO nanosheets affords a good adsorptive capacity for RhB molecules, facilitated charge transfer, and suppressed recombination of electron–hole pairs. These figures of merit lead to an enhanced photocatalytic performance over AgI@RGO. This work opens new possibilities for the development of highly efficient and stable visible‐light‐driven composite photocatalysts for environmental purification.

NiS nanoparticle decorated MoS2 nanosheets as efficient promoters for enhanced solar H2 evolution over ZnxCd1−xS nanorods

Facilitating charge separation as well as surface redox reactions is central to improve semiconductor catalyzed solar hydrogen generation. Photocatalysts comprising intimately interfaced photoabsorbers and co-promoters for the enhanced photocatalytic efficiency have gained much attention. In this paper, efficient promoters of NiS decorated MoS2 nanosheets (MoS2/NiS) coupled with ZnxCd1−xS nanorods have been prepared through a convenient hydrothermal method. The as-achieved Zn0.2Cd0.8S/MoS2/NiS nanohybrids exhibited a high solar H2 evolution activity with a rate of 41.29 mmol gcat−1 h−1 and the apparent quantum efficiency of 19% at a wavelength of 435 nm. The result represents one of the most active photocatalysts with noble-metal-free cocatalysts. The synergetic effects of MoS2 and NiS are responsible for the enhanced photocatalytic activity, and the presence of NiS further promotes the photo-induced electron-transfer from Zn0.2Cd0.8S to MoS2. This work opens an avenue for the design of efficient cocatalysts towards the enhancement of photocatalytic performance.

Solar-driven Pt modified hollow structured CdS photocatalyst for efficient hydrogen evolution

Hollow CdS nanostructures have been synthesized by a two-step ionic exchange route, which consists of a first synthesis of Ag2S intermediated hollow frames derived from the reaction of S2− ions with AgCl cube-tetrapods, and a subsequent ion-exchange conversion of the obtained Ag2S to CdS hollow nanoframes. The investigation of the corresponding transformation process with scanning electronic microscopy (SEM) revealed that the obtained CdS particles preserved the framework of the original template. The solar-driven hollow structured CdS modified with 5% (w/w) of promoter of Pt nanoparticles/nanoclusters manifested a high hydrogen evolution rate of 10.07 mmol h−1 g−1, corresponding to the apparent quantum yield of 9.6% measured at a single length of 435 nm, which is due to efficient charge separation, fast transport of the photogenerated carriers, and fast photochemical reaction at the CdS/Pt/electrolyte interfaces. The present work can benefit the development of other hollow structured nano-photocatalysts with high efficiency towards new energy applications.

Synthesis of AgInS2-xAg2S-yZnS-zIn6S7 (x, y, z = 0, or 1) Nanocomposites with Composition-Dependent Activity towards Solar Hydrogen Evolution

Metal sulfides-based nanomaterials have been used as a class of efficient solar driven photocatalysts. However, the H2-production rate observed over these photocatalysts remains problematic. Here, the AgInS2-xAg2S-yZnS-zIn6S7 (x, y, z = 0 or 1) nanocomposites with controlled compositions have been successfully prepared by a simple hydrothermal method with AgI polyhedrons as silver source. The obtained AgInS2-xAg2S-yZnS-zIn6S7 nanocomposites showed a composition-dependent activity for H2 evolution from aqueous solution under simulated sun-light irradiation. The results showed that the optimized product of AgInS2-Ag2S-ZnS nanoparticles synthesized with the precursor ratio of Ag:Zn = 1:1 exhibited the highest H2 evolution rate of 5.4 mmol·g−1·h−1. Furthermore, the catalyst can be used for 20 h without loss of activity, showing its high stability. It opens a new path to achieve highly efficient solar photocatalyst for H2 evolution from water splitting.