Sodium-Directed Photon-Induced Assembly Strategy for Preparing Multisite Catalysts with High Atomic Utilization Efficiency.

Integrating different reaction sites offers new prospects to address the difficulties in single-atom catalysis, but the precise regulation of active sites at the atomic level remains challenging. Here, we demonstrate a sodium-directed photon-induced assembly (SPA) strategy for boosting the atomic utilization efficiency of single-atom catalysts (SACs) by constructing multifarious Au sites on TiO2 substrate. Na+ was employed as the crucial cement to direct Au single atoms onto TiO2, while the light-induced electron transfer from excited TiO2 to Au(Na+) ensembles contributed to the self-assembly formation of Au nanoclusters. The synergism between plasmonic near-field and Schottky junction enabled the cascade electron transfer for charge separation, which was further enhanced by oxygen vacancies in TiO2. Our dual-site photocatalysts exhibited a nearly 2 orders of magnitude improvement in the hydrogen evolution activity under simulated solar light, with a striking turnover frequency (TOF) value of 1533 h-1 that exceeded other Au/TiO2-based photocatalysts reported. Our SPA strategy can be easily extended to prepare a wide range of metal-coupled nanostructures with enhanced performance for diverse catalytic reactions. Thus, this study provides a well-defined platform to extend the boundaries of SACs for multisite catalysis through harnessing metal-support interactions.

Porous Molybdenum Compound Design for Strong Microwave Absorption.

Exploring highly efficient microwave absorption (MA) materials with a facile preparation method is of great significance for tackling electromagnetic pollution and remains a challenge. Herein, ternary MoO2/Mo2C/Mo2N composites with porous structures are fabricated by a simple precursor pyrolysis process. The unique structure and multiple components, which could generate sufficient heterogeneous interfaces, are conducive to improve impedance matching, trigger polarization loss, and strengthen conduction loss. Profiting from the synergistic effect of multiple dissipation mechanisms, the composites exhibit exceedingly good MA performance. The minimum reflection loss value reaches -38.0 dB at 10.4 GHz when the thickness is 2.0 mm, and the maximum effective absorbing bandwidth is 4.11 GHz ranged from 12.41 to 16.52 GHz when the thickness is 1.5 mm. These strategies pave opportunities for rational design of Mo-related composites for high-efficiency electromagnetic-wave absorption performance.

Combining non-thermal plasma technology with photocatalysis: a critical review.

Due to the excellent application prospects in the fields of new energy generation and environmental remediation, photocatalysis technology has attracted the increasing attention of researchers. Although significant progress has been made in the past decades, the practical application of this technology is still restricted by the moderate catalytic efficiency. To improve the performance of catalysts, new methods are extremely required for the controllable synthesis of high-efficiency catalysts. To further comprehend the relationship between material structure and catalytic activity, the surface active sites of catalysts should be regulated at the atomic and molecular levels. As the fourth state of matter, plasma can generate diverse active species with low energy consumption. As a subset of plasmas, non-thermal plasma (NTP), defined by the great temperature difference between ions (near room temperature) and electrons (usually hotter than 2 orders of magnitude), contributes to the rapid synthesis of functional nanomaterials under relatively mild conditions. Furthermore, NTP has been widely used for the surface modification of materials. Therefore, the combination of NTP and photocatalysis is expected to provide an ideal approach to synthesize high-performance catalysts and precisely customize their surface structures, which is becoming a new direction in the field of catalysis research. This paper fundamentally reviews the progress in the combination of NTP with photocatalysis for versatile applications. Beginning with the principles of photocatalysis and plasma technology, the application of NTP for catalyst synthesis, the plasma-assisted modification of surface actives sites, and the impact of plasma-involved processes on the catalytic performance are discussed, which will provide useful insights into the performance enhancement of catalysts via plasma-assisted processes.

Effect of Single-Atom Cocatalysts on the Activity of Faceted TiO2 Photocatalysts.

The synergetic contribution of crystal facets and atomic cocatalysts toward the photoactivity of TiO2 was fundamentally investigated. Atomic-level dispersed Pt and Au were deposited onto 001-faceted and 101-faceted TiO2, separately. When used as photocatalysts for photocatalytic H2 production, Pt/TiO2-001 showed 1156 and 3 times higher H2 evolution rate than that of cocatalyst-free TiO2-001 and Pt-cocatalyzed TiO2-101. The significantly improved photocatalytic performance was attributed to the efficient separation of high-energy electrons and the sufficient exposure of reactive sites. This study demonstrates a promising way to design single-atom-assisted photocatalysts for high-efficiency water splitting.

Interfacial Charge Transfer in MoS2/TiO2 Heterostructured Photocatalysts: The Impact of Crystal Facets and Defects.

One of the most challenging issues in photocatalytic hydrogen evolution is to efficiently separate photocharge carriers. Although MoS2 loading could effectively improve the photoactivity of TiO2, a fundamental understanding of the charge transfer process between TiO2 and MoS2 is still lacking. Herein, TiO2 photocatalysts with different exposed facets were used to construct MoS2/TiO2 heterostructures. XPS, ESR, together with PL measurements evidenced the Type II electron transfer from MoS2 to {001}-TiO2. Differently, electron-rich characteristic of {101}-faceted TiO2 were beneficial for the direct Z-scheme recombination of electrons in TiO2 with holes in MoS2. This synergetic effect between facet engineering and oxygen vacancies resulted in more than one order of magnitude enhanced hydrogen evolution rate. This finding revealed the elevating mechanism of constructing high-performance MoS2/TiO2 heterojunction based on facet and defect engineering.

Synthesis of Pd nanorod arrays on Au nanoframes for excellent ethanol electrooxidation.

Au-Pd hollow nanostructures have attracted a lot of attention because of their excellent ethanol electrooxidation performance. Herein, we report a facile preparation of Au nanoframe@Pd array electrocatalysts in the presence of cetylpyridinium chloride. The reduced Pd atoms were directed to mainly deposit on the surface of the Au nanoframes in the form of rods, leading to the formation of Au nanoframe@Pd arrays with a super-large specific surface area. The red shift and damping of the plasmon peak were ascribed to the deposition of the Pd arrays on the surface of the Au nanoframes and nanobipyramids, which was verified by electrodynamic simulations. Surfactants, temperature and reaction time determine the growth process and thereby the architecture of the obtained Au-Pd hollow nanostructures. Compared with the Au nanoframe@Pd nanostructures and Au nanobipyramid@Pd arrays, the Au nanoframe@Pd arrays exhibit an enhanced electrocatalytic performance towards ethanol electrooxidation due to an abundance of catalytic active sites. The Au NF@Pd arrays display 4.1 times higher specific activity and 13.7 times higher mass activity than the commercial Pd/C electrocatalyst. Moreover, the nanostructure shows improved stability towards the ethanol oxidation reaction. This study enriches the manufacturing technology to increase the active sites of noble metal nanocatalysts and promotes the development of direct ethanol fuel cells.