Jianzhi Gao

Three-dimensional Ag2O/Bi5O7I p–n heterojunction photocatalyst harnessing UV–vis–NIR broad spectrum for photodegradation of organic pollutants

Ag2O nanoparticles-loaded Bi5O7I microspheres forming a three dimensional Ag2O/Bi5O7I p-n heterojunction photocatalyst with wide-spectrum response were synthesized in this study. The results of transmission electron microscopy observations revealed that the Ag2O nanoparticles with the diameter of ca. 10-20nm were distributed on the surfaces of Bi5O7I nanosheets. The as-synthesized Ag2O/Bi5O7I exhibited an excellent wide-spectrum response to wavelengths ranging from ultraviolet (UV) to near-infrared (NIR), indicating its potential for effective utilization of solar energy. Compared with pure Bi5O7I, the Ag2O/Bi5O7I composite also demonstrated excellent photocatalytic activity for the degradation of Bisphenol A and phenol in aqueous solution under visible LED light irradiation. Among samples, the 20% Ag2O/Bi5O7I composite photocatalyst showed the highest photocatalytic activity for the degradation of Bisphenol A and phenol in aqueous solution. In addition, the 20% Ag2O/Bi5O7I composite also exhibited a photocatalytic activity for the degradation of Bisphenol A under NIR light irradiation. The improved photocatalytic activity is attributed to the formation of a p-n heterojunction between Ag2O and Bi5O7I, allowing the efficient utilization of solar energy (from UV to NIR) and high separation efficiency of photogenerated electron-hole pairs. The present work is desirable to explore a possible avenue for the full utilization of solar energy.

One-step molten-salt method fabricated Bi2Ti2O7/Bi4Ti3O12 composites with enhanced photocatalytic activity

In this work, Bi2Ti2O7/Bi4Ti3O12 composite photocatalysts composed of Bi2Ti2O7 sub-micron-sized particles and Bi4Ti3O12 nanosheets with exposed {001} facets, were synthesized by a one-step molten salt method. The contents of Bi2Ti2O7 in the Bi2Ti2O7/Bi4Ti3O12 composites were adjusted by the Bi/Ti molar ratio of raw materials. The structure, morphology and optical absorption properties were characterized by XRD, SEM, TEM, HRTEM and UV–Vis diffuse reflectance. Compared with pure Bi4Ti3O12, the as-prepared Bi2Ti2O7/Bi4Ti3O12 composite (for the Bi/Ti ratio ~4:3.2) exhibit more excellent photocatalytic activities in the degradation of methyl orange (MO), Rhodamine B (RhB) and mixed dyes (RhB and MO) in aqueous solutions under simulated solar light irradiation. Furthermore, for the mixed dye solution, the as-prepared composite photocatalysts show preferential decomposition of MO in comparison to RhB. To detect the reactive species, the scavenger tests for the composite photocatalysts were carried out and the results indicate that the photogenerated h+ would play an important role in the degradation of RhB and MO dyes. Based on the experimental results in this work, the possible photocatalytic degradation mechanism of Bi2Ti2O7/Bi4Ti3O12 composites was also discussed.

One-step solvothermal synthesis of Fe-doped BiOI film with enhanced photocatalytic performance

Ultrathin nanosheets consisting of Fe-doped BiOI were obtained on a FTO (SnO2:F) glass substrate via a simple solvothermal process. High-resolution transmission electron microscopic analysis indicates that the ultrathin nanosheets are exposed with {001} facets. The Fe-doped BiOI film has a higher photocatalytic activity for degrading Rhodamine B under visible light irradiation in comparison with the undoped BiOI films. The photocatalytic activity reached a maximum when the Fe doping concentration was 7%. It is believed that an optimal concentration of Fe3+ ions improves the electron–hole separation efficiency, hence improving the degradation rate of Rhodamine B. Scavenger test results indicate that the photo-generated h+ and ˙O2− play an important role in the degradation of Rhodamine B. A possible photocatalytic degradation mechanism for Rhodamine B by Fe-doped BiOI film is presented.

Preparation of hollow Ag/AgCl/BiOCl microspheres with enhanced photocatalytic activity for methyl orange under LED light irradiation

Hollow Ag/AgCl/BiOCl microspheres photocatalysts have been successfully fabricated by anchoring Ag/AgCl nanoparticles on the surfaces of BiOCl microstructures. The as-synthesized composites greatly enhanced photocatalytic performance in the degradation of methyl orange under LED light irradiation, which was much higher than the Ag/AgCl or pure BiOCl. The photocatalytic mechanisms were analyzed by active species trapping experiment, where the photogenerated hole played critical roles in the reacting process. Our results revealed that the surface plasmon resonance of metallic Ag and heterojunction of Ag/AgCl/BiOCl photocatalysts had a great effect on the photocatalytic activity.

Phosphorus-doped silicon nanorod anodes for high power lithium-ion batteries

Heavy-phosphorus-doped silicon anodes were fabricated on CuO nanorods for application in high power lithium-ion batteries. Since the conductivity of lithiated CuO is significantly better than that of CuO, after the first discharge, the voltage cut-off window was then set to the range covering only the discharge–charge range of Si. Thus, the CuO core was in situ lithiated and acts merely as the electronic conductor in the following cycles. The Si anode presented herein exhibited a capacity of 990 mAh/g at the rate of 9 A/g after 100 cycles. The anode also presented a stable rate performance even at a current density as high as 20 A/g.

Self-assembly directed one-step synthesis of [4]radialene on Cu(100) surfaces

The synthetic challenges of radialenes have precluded their practical applications. Here, we report a one-step synthetic protocol of [4]radialene on a copper surface. High-resolution scanning tunneling microscopy measurements reveal that such catalytic reaction proceeds readily with high selectivity at the temperature below 120 K. First-principles calculations show that the reaction pathway is characterized by firstly the cooperative inter-molecular hydrogen tautomerization and then the C–C bond formation. The feasibility of such cyclotetramerization reaction can be interpreted by the surface effect of Cu(100), which firstly plays an important role in directing the molecular assembly and then serves as an active catalyst in the hydrogen tautomerization and C–C coupling processes. This work presents not only a novel strategy to the scant number of synthetic methods to produce [4]radialenes via a novel [1 + 1 + 1 + 1] reaction pathway, but also a successful example of C–C bond coupling reactions guided by the surface-induced C–H/π assembly.Radialenes have distinct structural, electronic and chemical properties from other hydrocarbons, but their synthesis remains a challenge. Here, the authors report a copper catalyzed one-step synthetic protocol of [4]radialene via the cyclotetramerization of phenylacetylene molecules upon thermal activation.

Probing Phase Evolutions of Au-Methyl-Propyl-Thiolate Self-Assembled Monolayers on Au(111) at the Molecular Level

A self-assembled monolayer (SAM) consisting of a mixture of CH3S-Au-SCH3, CH3S-Au-S(CH2)2CH3, and CH3(CH2)2S-Au-S(CH2)2CH3 was studied systematically using scanning tunneling microscopy and density functional calculations. We find that the SAM is subjected to frequent changes at the molecular level on the time scale of ∼minutes. The presence of CH3S or CH3S-Au as a dissociation product of CH3S-Au-SCH3 plays a key role in the dynamical behavior of the mixed SAM. Slow phase separation takes place at room temperature over hours to days, leading to the formation of methyl-thiolate-rich and propyl-thiolate-rich phases. Our results provide new insights into the chemistry of the thiolate-Au interface, especially for ligand exchange reaction in the RS-Au-SR staple motif.