富勒烯[60]的光化学反应研究

从光物理出发 ,综述了近几年富勒烯 [6 0 ]的光化学反应研究进展。 C60 能发生诸多的光化学反应 :( 1 )光氧化 ;( 2 )光氢化还原 ;( 3) [2 + 2 ]光环化加成 ;( 4)与叔胺的光加成 ;( 5 )与氨基酸的光加成 ;( 6 )与金属有机化合物的光加成。

Octahedral Cu_2O-modified TiO_2 nanotube arrays for efficient photocatalytic reduction of CO_2

A photocatalyst composed of TiO 2 nanotube arrays（TNTs） and octahedral Cu2 O nanoparticles was fabricated,and its performance in the photocatalytic reduction of CO2 under visible and simulated solar irradiation was studied. The average nanotube diameter and length was 100 nm and 5 μm,respectively. The different amount of octahedral Cu2 O modified TNTs were obtained by varying electrochemical deposition time. TNTs modified with an optimized amount of Cu2 O nanoparticles exhibited high efficiency in the photocatalysis,and the predominant hydrocarbon product was methane. The methane yield increased with increasing Cu2 O content of the catalyst up to a certain deposition time,and decreased with further increase in Cu2 O deposition time. Insufficient deposition time（5 min） resulted in a small amount of Cu2 O nanoparticles on the TNTs,leading to the disadvantage of harvesting light. However,excess deposition time（45 min） gave rise to entire TNT surface being most covered with Cu2 O nanoparticles with large sizes,inconvenient for the transport of photo-generated carriers. The highest methane yield under simulated solar and visible light irradiation was observed for the catalysts prepared at a Cu2 O deposition time of 15 and 30 min respectively. The morphology,crystallization,photoresponse and electrochemical properties of the catalyst were characterized to understand the mechanism of its high photocatalytic activity. The TNT structure provided abundant active sites for the adsorption of reactants,and promoted the transport of photogenerated carriers that improved charge separation. Modifying the TNTs with octahedral Cu2 O nanoparticles promoted light absorption,and prevented the hydrocarbon product from oxidation. These factors provided the Cu2O-modified TNT photocatalyst with high efficiency in the reduction of CO2,without requiring co-catalysts or sacrificial agents.

Synthesis of TiO_2 mesocrystal film with enhanced photocatalytic activity

TiO2 mesocrystals can considerably enhance charge separation owing to their oriented superstructures,with fewer internal defects and porous properties providing more active sites.In this work,we prepared TiO2 mesocrystal films by a direct annealing method.The morphology and crystal phase of the film were controlled by adjusting the ratio of NH4F and the calcination temperature.Moreover,we found that Au nanoparticles loaded on a TiO2 mesocrystal film enabled highly efficient visible light photocatalytic properties.The photocatalytic activities were studied by hydrogen generation and photoreduction of Cr(VI).This work represents a considerable advance in the development and application of the TiO2 mesocrystals.

Fabrication of hierarchical ZnIn2S4@CNO nanosheets for photocatalytic hydrogen production and CO2 photoreduction

Photocatalytic H2 production and CO2 reduction have attracted considerable attention for clean energy development.In this work,we designed an efficient photocatalyst by integrating lamellar oxygen-doped carbon nitride(CNO)nanosheets into ZnIn2S4(ZIS)microflowers by a one-step hydrothermal method.A well-fitted 2D hierarchical hybrid heterostructure was fabricated.Under visible light irradiation,the ZIS@CNO composite with 40 wt%CNO(ZC 40%)showed the highest hydrogen evolution rate from water(188.4μmol·h-1),which was approximately 2.1 times higher than those of CNO and ZIS(88.6 and 90.2μmol·h-1,respectively).Furthermore,the selective CO production rates of ZC 40%(12.69μmol·h-1)were 2.2 and 14.0 times higher than those of ZIS(5.85μmol·h-1)and CNO(0.91μmol·h-1),respectively,and the CH4 production rate of ZC 40%was 1.18μmol·h-1.This enhanced photocatalytic activity of CNO@ZIS is due mainly to the formation of a heterostructure that can promote the transfer of photoinduced electrons and holes between CNO and ZIS,thereby efficiently avoiding recombination of electron-hole pairs.

Design and applications of hollow‐structured nanomaterials for photocatalytic H2 evolution and CO2 reduction

Photocatalysis is considered a prospective way to alleviate the energy crisis and environmental pollution.It is therefore extremely important to design highly efficient photocatalysts for catalytic systems.In recent years,hollow‐structured materials have attracted considerable interest for application in energy conversion fields owing to their large specific surface areas,improved light absorption,and shortened charge carrier transfer path.Because they contain inner and outer surfaces,hollow‐structured materials can provide a superior platform for the deposition of other components.A number of hollow‐structured hierarchical systems have been designed and fabricated in recent decades.It is important to rationally design and construct complex hierarchical structures.In this review,general preparation approaches for hollow‐structured materials are presented,followed by a summary of the recent synthesis methods and mechanisms of typical hollow‐structured materials for applications in the photocatalytic field.Complex hollow‐structured hierarchical photocatalysts are classified into two types,hollow cocatalyst‐based and hollow host photocatalyst‐based,and the design principle and analysis of the photocatalytic reaction mechanism for photocatalytic H2 evolution and CO_(2) reduction are also introduced.The effects of hollow‐structured materials have also been investigated.This review provides a reference for the rational construction of advanced,highly efficient photocatalytic materials.

MXenes as noble-metal-alternative co-catalysts in photocatalysis

Photocatalysis has become a focal point in research as a clean and sustainable technology with the potential to solve environmental problems and energy crises.The loading of noble-metal co-catalysts can substantially improve the photocatalytic efficiency of semiconductors.Because the high cost and scarcity of noble metals markedly limit their large-scale applications,finding a noble-metal-alternative co-catalyst is crucial.MXene,a novel 2D transition metal material,has attracted considerable attention as a promising substitute for noble metal co-catalysts owing to its cost-efficiency,unique 2D layered structure,and excellent electrical,optical,and thermodynamic properties.This review focuses on the latest advancements in research on MXenes as co-catalysts in relatively popular photocatalytic applications(hydrogen production,CO2 reduction,nitrogen fixation,and organic pollutant oxidation).The synthesis methods and photocatalytic mechanisms of MXenes as co-catalysts are also summarized according to the type of MXene-based material.Finally,the crucial opportunities and challenges in the prospective development of MXene-based photocatalysts are outlined.We emphasize that modern techniques should be used to demonstrate the effects of MXenes on photocatalysis and that the photocatalytic activity of MXene-based photocatalysts can be further improved using defective engineering and recent phenomena such as the localized surface plasmon resonance effect and single-atom catalysis.

Layered double hydroxide photocatalysts for solar fuel production

Splitting water or reducing CO_(2) via semiconductor photocatalysis to produce H2 or hydrocarbon fuels through the direct utilization of solar energy is a promising approach to mitigating the current fossil fuel energy crisis and environmental challenges.It enables not only the realization of clean,renewable,and high-heating-value solar fuels,but also the reduction of CO_(2) emissions.Layered double hydroxides(LDHs)are a type of two-dimensional anionic clay with a brucite-like structure,and are characterized by a unique,delaminable,multidimensional,layered structure;tunable intralayer metal cations;and exchangeable interlayer guest anions.Therefore,it has been widely investigated in the fields of CO_(2) reduction,photoelectrocatalytic water oxidation,and water photolysis to produce H2.However,the low carrier mobility and poor quantum efficiency of pure LDH limit its application.An increasing number of scholars are exploring methods to obtain LDH-based photocatalysts with high energy conversion efficiency,such as assembling photoactive components into LDH laminates,designing multidimensional structures,or coupling different types of semiconductors to construct heterojunctions.This review first summarizes the main characteristics of LDH,i.e.,metal-cation tunability,intercalated guest-anion substitutability,thermal decomposability,memory effect,multidimensionality,and delaminability.Second,LDHs,LDH-based composites(metal sulfide-LDH composites,metal oxide-LDH composites,graphite phase carbon nitride-LDH composites),ternary LDH-based composites,and mixed-metal oxides for splitting water to produce H_(2) are reviewed.Third,graphite phase carbon nitride-LDH composites,MgAl-LDH composites,CuZn-LDH composites,and other semiconductor-LDH composites for CO_(2) reduction are introduced.Although the field of LDH-based photocatalysts has advanced considerably,the photocatalytic mechanism of LDHs has not been thoroughly elucidated;moreover,the photocatalytic active sites,the synergy between different components,and the interfacial reaction mechanism of LDH-based photocatalysts require further investigation.Therefore,LDH composite materials for photocatalysis could be developed through structural regulation and function-oriented design to investigate the effects of different components and interface reactions,the influence of photogenerated carriers,and the impact of material composition on the physical and chemical properties of the LDH-based photocatalyst.

Nanostructured CdS for efficient photocatalytic H2 evolution: A review

Cadmium sulfide(Cd S)-based photocatalysts have attracted extensive attention owing to their strong visible light absorption,suitable band energy levels,and excellent electronic charge transportation properties.This review focuses on the recent progress related to the design,modification,and construction of Cd S-based photocatalysts with excellent photocatalytic H2 evolution performances.First,the basic concepts and mechanisms of photocatalytic H2 evolution are briefly introduced.Thereafter,the fundamental properties,important advancements,and bottlenecks of Cd S in photocatalytic H2 generation are presented in detail to provide an overview of the potential of this material.Subsequently,various modification strategies adopted for Cd S-based photocatalysts to yield solar H2 are discussed,among which the effective approaches aim at generating more charge carriers,promoting efficient charge separation,boosting interfacial charge transfer,accelerating charge utilization,and suppressing charge-induced self-photocorrosion.The critical factors governing the performance of the photocatalyst and the feasibility of each modification strategy toward shaping future research directions are comprehensively discussed with examples.Finally,the prospects and challenges encountered in developing nanostructured Cd S and Cd S-based nanocomposites in photocatalytic H2 evolution are presented.