Xiangqian Fan

Brand new P-doped g-C3N4: enhanced photocatalytic activity for H2 evolution and Rhodamine B degradation under visible light

P-doped g-C3N4 has been successfully synthesized using hexachlorocyclotriphosphazene, a low cost and environmentally benign compound, as phosphorus source, and guanidiniumhydrochloride as g-C3N4 precursor, via a thermally induced copolymerization route. The obtained P-doped g-C3N4 showed excellent photocatalytic performance both in the photoreduction of H2O to produce H2 and the photodegradation of Rhodamine B (RhB). H2 evolution rate on modified g-C3N4 reached 50.6 μmol h−1, which is 2.9 times higher than that of the pure g-C3N4. RhB (10 mg L−1) was completely photodegraded within 10 min. The structure and texture properties of the P-doped g-C3N4 have been investigated in detail by XRD, FTIR, TEM, EDS and STEM. With the results of XPS and 31P NMR, a possible existing form of P atom in the framework g-C3N4 has been put forward. The introduction of a P atom significantly changes the electronic property of g-C3N4 and suppresses the recombination of photogenerated charge carriers, thus improving its photocatalytic performance.

Highly selective CO2 photoreduction to CO over g-C3N4/Bi2WO6 composites under visible light

CO2 is highly stable and therefore extremely difficult to be reduced at room temperature even by photocatalysis. Herein, a series of g-C3N4/Bi2WO6 composites have been synthesized through a facile in situ hydrothermal approach, which demonstrated greatly enhanced response to visible light, and consequently a remarkably enhanced CO2 selective photoreduction to CO. The g-C3N4 content and synthesis parameters of these composites have been tuned to obtain the optimized photocatalytic activity with a peak CO production rate of 5.19 μmol g−1 h−1 under visible light irradiation at room temperature, which was 22 and 6.4 times that on pure g-C3N4 and Bi2WO6, respectively. Based on the matched band energy potentials between g-C3N4 and Bi2WO6 in the synthesized composites, a possible Z-scheme mechanism, which features a significantly promoted separation of photo-generated carriers under visible light irradiation by the composites, has been proposed to account for the distinctive CO2 photoreduction performance.

MoS2 quantum dot decorated g-C3N4 composite photocatalyst with enhanced hydrogen evolution performance

A novel MoS2 quantum dot (QD) decorated g-C3N4 (MoS2-QDs/CN) heterostructured photocatalyst has been synthesized via a simple wetness impregnation method. The as-prepared MoS2-QDs/CN composite exhibited strong absorption in the visible light region. Its photocatalytic activity on hydrogen evolution was evaluated by splitting water under visible light irradiation (λ > 420 nm). The highest H2 yield of 19.66 μmol h−1 was achieved on 50 mg 1 wt% MoS2-QDs/CN photocatalyst (loaded with 1 wt% Pt), which was 6.6 and 1.84 times those on pure g-C3N4 and 1 wt% Pt loaded g-C3N4, respectively.

Improved photocatalytic activity of g-C3N4 derived from cyanamide–urea solution

This paper describes the fabrication of g-C3N4 by the polymerization of cyanamide–urea solution at elevated temperatures. The textural properties and electronic band structure of the obtained g-C3N4 were investigated in detail. The photocatalytic activity for both oxidative and reductive reactions of the as-synthesized g-C3N4 was found to be enhanced as the polymerization temperature increase and the g-C3N4 obtained at 700 °C (CN-700) showed the best photocatalytic activity under visible-light (λ > 420 nm). Considering that the rather wide band gap (3.01 eV) of CN-700 disables the electron transition from the valence band to the conduction band by visible light (λ > 420 nm), it is believed the n–π* transition, which is alternatively proposed in this study, plays a key role in its photocatalytic activity. In light of this discovery, the variation of the electron-transition mechanism for g-C3N4 fabricated at different polymerization temperatures has been firstly investigated.

A post-grafting strategy to modify g-C3N4 with aromatic heterocycles for enhanced photocatalytic activity

A novel and facile post-grafting strategy, instead of conventional copolymerization, via a Schiff base chemical reaction between aldehyde and –NH2 groups has been developed to construct aromatic heterocycle-grafted graphitic carbon nitride (g-C3N4) photocatalysts for the first time. The high-resolution N 1s XPS spectrum and the CO2 TPD analysis confirmed the successful introduction of heterocycles and the reduced structural defects (unreacted –NH2 groups during the copolymerization modification of g-C3N4). The post-grafting of aromatic rings into the g-C3N4 network did not disrupt the original framework of g-C3N4, but effectively expanded its π-delocalized system, enlarged its surface area and promoted the separation and transfer of photo-excited charge carriers. As a result, the obtained copolymer composites exhibit significantly enhanced visible-light photocatalytic activity for H2 evolution over pristine g-C3N4. This strategy is general and can be used to graft large numbers of aromatic rings of different molecular structures onto g-C3N4.

Facile construction of CuFe2O4/g-C3N4 photocatalyst for enhanced visible-light hydrogen evolution

A new type of CuFe2O4/g-C3N4 composite photocatalyst has been prepared by a facile one-pot calcination approach using urea and a CuFe2O4 gel as precursors. In this composite, CuFe2O4 has been finely dispersed in g-C3N4 matrix, resulting in a much enhanced efficiency of the CuFe2O4/g-C3N4 heterostructure in photocatalytic H2 production by water splitting, under visible light. A peak H2 production rate of 76 μmol h−1 has been obtained, which is about 3 times that on pure g-C3N4 obtained from urea. This remarkable improvement can be attributed to the enhanced visible light absorbance, enlarged surface area and promoted charge carrier separation and transfer.

Amorphous Fe2+-rich FeOx loaded in mesoporous silica as a highly efficient heterogeneous Fenton catalyst

A simple physical-vapor-infiltration (PVI) method using ferrocene as the iron source, has been developed to load FeOx into the pore channels of mesoporous silica SBA-15. The obtained FeOx/SBA-15 composite has a high loading amount of FeOx (e.g. 26.64 wt% Fe content obtained at PVI duration 17 h and calcination temperature 450 °C) but unblocked pore channels thanks to the unique preparation strategy. The FeOx species are amorphous, rich of Fe(2+) and have been highly dispersed as a nanocoating onto the pore channel surface. The FeOx/SBA-15 composite was used as a heterogeneous Fenton catalyst to degrade Acid orange 7 (AO7). It showed a high catalytic activity and degradation efficiency, which was attributed to the high proportion of Fe(2+) in the amorphous FeOx and their favorable adsorption capability for the dye. The influences of the PVI duration, the calcination temperature and the Fenton reaction conditions (FeOx/SBA-15 dosages, H2O2 dosages and initial pH value) on the catalytic activity were investigated in detail.

A unique route to fabricate mesoporous carbon with abundant ferric species as a heterogeneous Fenton catalyst under neutral conditions

The incorporation of large amounts of metal oxide species into mesoporous carbon without pore blockage is still a challenge. Herein, a unique approach combining physical vapor infiltration (PVI) with hard-templating replication, has been developed to prepare mesoporous carbon immobilized with abundant and highly dispersed ferric species using ferrocene as a single source for both carbon and iron. As a heterogeneous Fenton catalyst, the as-synthesized mesoporous carbon Fe/mC-450-H, which was obtained at 450 °C in an H2 atmosphere, can efficiently adsorb and degrade methylene blue (MB) at neutral pH values with H2O2.

α-Ferrous oxalate dihydrate: a simple coordination polymer featuring photocatalytic and photo-initiated Fenton oxidations

As a kind of efficient photocatalyst, coordination polymers (CPs) have gained much attention in recent years. However, their safety issue and time-consuming synthesis impede their practical application. Here in this paper we first demonstrate the facile synthesis and photocatalytic degradation performance of 1D α-ferrous oxalate dihydrate (α-FOD), which is one of the simplest CPs. A unique two-pathway photocatalytic mechanism which combines traditional photocatalytic and photo-initiated Fenton oxidations has been proposed. The excellent photocatalytic performance and cost-effective fabrication make α-FOD a new promising candidate for the photocatalytic degradation of organic pollutants in practical applications.摘要最近, 配位聚合物作为一种引人注目的光催化剂已经引起了很多研究者的兴趣. 但是危险耗时的制备方法使它的应用受到了限制. 本文采用便捷的制备方法合成了一种简单的线性配位聚合物 “二水合草酸亚铁”, 并证实了其光催化降解染料的活性和能力. 同时, 我们提出了一种独特的结合了传统光催化氧化和光Fenton氧化的双途径催化氧化机理. 二水合草酸亚铁优异的光催化性能及其经济简单的合成方法, 使其有望成为一种有效的降解有机染料的光催化剂.