| How to utilize photocatalytic technique with high efficiency, low energy consumption,clean and no secondary pollution properties become a hot issue in the context of theuniversal crisis of energy shortage and environmental pollution. Recently, scientists aremaking great efforts to probe into the way to explore the highly efficient visible lightphotocatalytic materials. Among them, the ordered mesoporous metal oxides with highspecific surface area, ordered pore structure, adjustable aperture and the modified internalsurface are gaining popularity by the researchers. Many different morphologies,mesoporous structure and skeleton composition of ordered mesoporous structure have beensuccessful prepared and widely used in catalysis, sensing, energy and other fields,combining with the critical issues settlement of ordered mesoporous metal oxides ofcatalytic function, pore size adjustment, in-situ spectroscopic characterization andmolecular design, thereby promoted the development of photocatalytic technology. In thispaper, we discuss the preparation of mesoporous metal oxides and formation mechanism ofmesoporous structure. At the same time, the photocatalytic properties and potentialapplications of the mesoporous metal oxide photocatalysts have been systematicallyinvestigated under visible light irradiation. This study will contribute to the development ofnovel photocatalyst with high performance, and provide a new idea in the field of solarenergy conversion and basic theories of reference, the main research contents are asfollows:(1) Three-dimensionally ordered mesoporous WO3was successfully synthesized by ahydrothermal method using mesoporous silica KIT-6as a hard template andphosphotungstic acid as a precursor. Investigations of optical and photoelectrochemicalproperties showed that the mesoporous WO3was a n-type semiconductor with a band gapof2.6eV and demonstrated prompt, steady, and reproducible photocurrent responsesduring repeated on/off cycles of visible light illumination (λ>420nm). The mesoporous WO3modified by platinum nanoparticles could be used as a stable photocatalyst forphotoinducing O2evolution. Under visible light irradiation, the average O2evolution ratereached to34.5μmol g-1h-1with the presence of an electron acceptor of IO-3. This workdemonstrated a potential application of using mesoporous WO3modified by platinumnanoparticles as a novel photocatalyst in the field of solar energy conversion.(2) We report the synthesis, characterization, and photocatalysis of a novel composite,composed of high-ordered mesoporous WO3(m-WO3) and reduced graphene oxide(RGO). The superior contact between two moieties in the composites facilitates the chargecarrier separation and the evolution of oxygen. Under visible light irradiation, the amountof oxygen evolution from the optimized photocatalyst containing ca.6wt%RGO reachedto437.3μmol·g1, which was5.1times as high as that from m-WO3. The enhancement ofphotocatalytic activity could be ascribed to that RGO acts herein as a solid-state electronmediator, promoting the charge transportation and separation, as well as suppressing theelectron-hole recombination in the composite. This study might provide a prototype forconstructing a novel photocatalytic system by hybridizing graphene with a mesoporoussemiconductor for solar energy conversion.(3) The high-ordered N-doped mesoporous niobium oxide (NMNb) was prepared viaa facile solid state reaction method using urea as a nitrogen source. The inheritedmesoporous structure of NMNb making the N dopants effective incorporated in lattice ofmesoporous niobium oxide (MNb), result in a significant enhanced visible light response,corresponding to a reduced band gap of2.61eV. Subsequently, the optimized hydrogengeneration efficiency over N-doped MNb photocatalyst was14.8times as high as that fromN-P25under5h visible light irradiation with0.5wt%Pt as a cocatalyst. The improvedphotocatalytic activity of NMNb was mainly due to the ordered mesostructure could offermore active sites for the photocatalytic reaction, as well as accelerate the photogeneratedelectron-hole pairs transfer and separation. It is hoped that this study could promoteincreasing interest in designing N doped diverse structure of semiconductor photocatalystsfor solar water splitting.(4) Mesoporous cerium oxides were prepared by a hard templating method usingmesoporous silica dioxide (KIT-6) as the hard template, cerium nitrate as the source ofcerium. The photodegradation activity of m-CeO2/Bi powders was evaluated by using4-chlorophenol (4-CP) as pollutant targets under visible light irradiation (λ＞420nm). The results demonstrate that the m-CeO2/Bi photocatalyst equipped with high crystallinity andcontinuous pore channels, which benefit for the electron-hole pairs separation.Simultaneously, doped Bi could reduce the bandgap of the m-CeO2photocatalyst, therebyeffectively improve the visible light photocatalytic properties. The photodegradation yieldof4-CP was beyond91%under visible light irradiation for four hours. The photocatalystcan be recycled several times without losing its photocatalytic activity. |
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