Confinement of noble nanometals in a zeolite matrix is a promising way to special types of catalysts that show significant advantages in size control, site adjustment, and nano‐architecture design. ...The beauty of zeolite‐confined noble metals lies in their unique confinement effects on a molecular scale, and thus enables spatially confined catalysis akin to enzyme catalysis. In this Minireview, the confined synthesis strategies of zeolite‐confined noble metals will be briefly discussed, showing the processes, advantages, features, and mechanisms. The confined catalysis carried on zeolite‐confined noble metals will be summarized, and great emphasis will be paid to the confinement effects involving size, encapsulation, recognition, and synergy. Great progress of atomic sites in the size effect, supercage stabilization in the encapsulation effect, site adsorption in the recognition effect, and cascade reaction in the synergy effect are highlighted. This Minireview is concluded with challenges and opportunities in terms of the synthesis of zeolite‐confined noble metals and their applications to design multifunctional catalysts with high catalytic activity, selectivity, and stability.
The beauty of zeolite‐confined noble metals lies in their unique confinement effects on a molecular scale, and thus enables spatially confined catalysis akin to enzyme catalysis. This Minireview summarizes synthesis strategies and targeted catalysis applications for multifunctional zeolite‐confined noble metal catalysts.
In the present work, the spontaneous dewetting of thin Au layers on single crystalline anatase nanosheets into narrow‐disperse Au nanoparticles is investigated. Patterns of the Au particles can be ...formed on the main facets of anatase that provide a high co‐catalytic activity for photocatalytic generation of H2. Dewetting is distinctly influenced by the respective facets (001) and (101), the deposit thickness, and secondary thermal dewetting, but most strongly by the surface termination of the nanosheets. Fluoride termination not only leads to an enhanced Au‐phobic behavior but strongly affects the co‐catalytic activity for photocatalytic generation of H2. While fluoride termination with or without Au decoration is detrimental for hole transfer, the interplay of the Au co‐catalyst and surface fluoride yields highly beneficial effect for electron transfer. This results in a three‐times higher photocatalytic H2 production for the F‐terminated surface. The findings suggest that dewetting of Au on surface fluorinated TiO2 is an effective way to modulate surface dewetting and achieve a strongly enhanced photocatalytic activity.
This study presents an investigation on the spontaneous dewetting behavior of thin Au layers on single‐crystalline anatase nanosheets. Dewetting is facet‐dependent and influenced by F‐termination. For photocatalytic H2 production, F‐termination and dewetted Au exhibit a strong co‐catalytic synergy effect that leads to a significant improvement of the H2 evolution rate.
The homojunction of oxygen/metal vacancies and its interfacial n–p effect on the physiochemical properties are rarely reported. Interfacial n–p homojunctions of TiO2 are fabricated by directly ...decorating interfacial p‐type titanium‐defected TiO2 around n‐type oxygen‐defected TiO2 nanocrystals in amorphous–anatase homogeneous nanostructures. Experimental measurements and theoretical calculations on the cell lattice parameters show that the homojunction of oxygen and titanium vacancies changes the charge density of TiO2; a strong EPR signal caused by oxygen vacancies and an unreported strong titanium vacancies signal of 2D 1H TQ‐SQ MAS NMR are present. Amorphous–anatase TiO2 shows significant performance regarding the photogeneration current, photocatalysis, and energy storage, owing to interfacial n‐type to p‐type conductivity with high charge mobility and less structural confinement of amorphous clusters. A new “homojunction of oxygen and titanium vacancies” concept, characteristics, and mechanism are proposed at an atomic‐/nanoscale to clarify the generation of oxygen vacancies and titanium vacancies as well as the interface electron transfer.
The homojunction of oxygen and titanium vacancies developed in the amorphous–anatase interface of nanostructured TiO2 results in a unique n–p electronic transmission, which is mostly preferred to the mobility of electronic charge carriers. It also contributes to significant performance regarding photogeneration current, photocatalysis, and energy storage.
An electrocatalyst composed of RuO2 surrounded by interfacial carbon, is synthesized through controllable oxidization‐calcination. This electrocatalyst provides efficient charge transfer, numerous ...active sites, and promising activity for pH‐universal electrocatalytic overall seawater splitting. An electrolyzer with this catalyst gives current densities of 10 mA cm−2 at a record low cell voltage of 1.52 V, and shows excellent durability at current densities of 10 mA cm−2 for up to 100 h. Based on the results, a mechanism for the catalytic activity of the composite is proposed. Finally, a solar‐driven system is assembled and used for overall seawater splitting, showing 95% Faraday efficiency.
An electrocatalyst composed of RuO2 surrounded by interfacial carbon is synthesized through controllable oxidization‐calcination. The interfacial carbon in RuO2/carbon compositions can provide efficient charge transfer and enhanced structural stability for the RuO2, which exhibits promising activity for pH‐universal electrocatalytic overall seawater splitting and its application in the solar‐driven electrolyzer.
Photodriven seawater splitting is considered to be one of the most promising techniques for sustainable hydrogen production. However, the high salinity of seawater would deactivate catalysts and ...consume the photogenerated carriers. Metal vacancies in metal oxide semiconductors are critical to directed electron transfer and high salinity resistance; they are thus desirable but remain a challenge. We demonstrate a facile controllable calcination approach to synthesize TiO2 nanofibers with rich Ti vacancies with excellent photo/electro performances and long‐time stability in photodriven seawater splitting, including photocatalysis and photo‐electrocatalysis. Experimental measurements and theoretical calculations reveal the formation of titanium vacancies, as well as unidirectional electron trap and superior H+ adsorption ability for efficient charge transfer and resistance to corrosion by seawater. Therefore, atomic‐/nanoscale characteristics and mechanism have been proposed to clarify the generation of titanium vacancies and the corresponding interfacial electron transfer.
Erosion of corrosion: TiO2 nanofibers with rich Ti vacancies have been designed by a facile controllable calcination approach. They exhibit efficient charge transfer and resistance to corrosion by seawater owing to a unidirectional electron trap and superior H+ adsorption; which contribute to excellent activity and long‐time stability in photodriven seawater splitting. This study could provide a promising strategy for the design of efficient semiconductors in marine applications.
Dual active sites from acidic zeolite and Pd are not only capable of catalyzing multiple type of reactions, but could also generate unique functions owing to the synergy between metals and acidic ...sites. However, there are only a few reports on the investigation of the synergy of acid/Pd dual sites in TS-1. Herein, TS-1 confined Pd catalyst with mesoporous silica shell (Pd@TS-1 @meso-SiO2) has been successfully synthesized and its synergy effect contributes to the enhanced conversion rate (19.2%) and selectivity (74.7%) on styrene oxidation. The interaction between Pd and TS-1 has been investigated by EPR and 1H NMR techniques, the experimental measurements show an obvious change in the signal distribution of weakly acidic terminal hydroxyls and hydrogen-bonding silanols. The schematic illustration of selective styrene oxidation in the model of Pd@TS-1 @meso-SiO2 is proposed to clarify the synergistic effect on styrene oxidation between TS-1 and Pd nanoparticles at an atomic-/nanoscale.
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•A dual active sites catalyst with acid sites and Pd nanometals is synthesized.•The catalyst shows higher conversion and selectivity ratio in styrene oxidation.•The synergy effect of dual active sites is investigated by 1H NMR techniques.•A possible schematic illustration of the selective styrene oxidation is proposed.
TiO2 used as a light‐absorbing semiconductor represents the classic benchmark for photocatalytic solar energy conversion and many other photocatalytic reactions. Various strategies are developed to ...improve the photoresponse of TiO2‐based materials, such as bandgap engineering or surface sensitization in combination with nanostructuring and geometry optimization. The present feature article is focused on direct and indirect approaches involving bulk or surface fluorine used to tune the surface chemistry, electronic structure, and the morphology of TiO2 photocatalysts. A comprehensive overview is provided on fluorine effects on TiO2, involving morphology modifications, and how surface or bulk fluorine affect the photocatalytic performance of TiO2. After outlining some basic interaction principles of F and TiO2, characterization techniques for different fluorine species are discussed. It is reviewed how fluorine during crystal growth mediates the morphology of TiO2; then how surface fluorination and doping fluorine effects can be beneficially utilized in photocatalysis are discussed. Finally, synergistic effects between fluorine and cocatalyst are discussed, for example, the use of lattice fluorine species to stabilize Pt single‐atom cocatalysts. Finally, the challenges and outlook on further advancing the development of fluorine effects are highlighted.
TiO2 semiconductors are very promising photocatalysts in solar energy conversion and increasing its solar conversion efficiency is greatly demanded. Fluorine species involved in the design of TiO2 is capable of tuning the structural properties of TiO2. This perspective summarizes the direct and indirect effect of fluorine on photocatalytic performance of TiO2, along with future needs and opportunities in this field.
Hierarchically dual‐mesoporous TiO2 microspheres have been synthesized by a solvothermal process in the presence of 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF4) and diethylenetriamine ...(DETA) as co‐templates. Secondary mesostructured defects in the hierarchical TiO2 microspheres produce oxygen vacancies, which not only significantly enhance photocatalytic activity in the degradation of methylene blue (1.7 times that with P25) and acetone (2.9 times that with P25), but are also beneficial for lithium storage. Moreover, we propose a mechanism to rationalize the role of this dual mesoporosity of the TiO2 microspheres in enhancing molecular diffusion, ion transportation, and electronic transitions.
Beneficial dual mesoporosity: Hierarchically dual‐mesoporous TiO2 has been synthesized by a co‐templating method. Its mesostructured defects caused by an ionic liquid lead to a high level of oxygen vacancies (see graphic), which significantly enhance its photoelectrochemical performance.
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