Peilu Zhao

Gas sensing with hollow α-Fe2O3 urchin-like spheres prepared via template-free hydrothermal synthesis

Hollow α-Fe2O3 urchin-like spheres were prepared by annealing the FeOOH precursor, which was synthesized via a template-free hydrothermal method. Interestingly, the size and hollowness of spheres could be tailored by adjusting the concentration of ferric sulphate. The sensing properties of the as-prepared samples were investigated.

Bilayered photoanode from rutile TiO2 nanorods and hierarchical anatase TiO2 hollow spheres: a candidate for enhanced efficiency dye sensitized solar cells

A bilayered photoanode for dye-sensitized solar cells (DSSCs) was constructed with the top layer using TiO2 hierarchical hollow spheres (THS) and the second layer based on 3D TiO2 nanorods. The anatase THS with diameters of 400–600 nm and with a specific surface area of 100.3 m2 g−1 were synthesized via a simple hydrothermal method. As a light scattering layer, the THS could provide dual-functions of adsorbing dye molecules and strong light-harvesting efficiency. The 3D TiO2 nanorods consisting of 1D vertically aligned rutile TiO2 nanorods (TNR) and 3D TiO2 nanoflowers (TNF) were synthesized by a one-step hydrothermal method. The unique 3D nanostructure could offer a better light scattering capability, faster electron transport and lower electron recombination. Consequentially, the bilayered cell exhibited a much higher short-circuit photocurrent density of 15.60 mA cm−2 and energy conversion efficiency of 7.50%, which indicated a 108.6% and a 36.8% increment of cell efficiency compared to the TNR-F electrode (7.36 mA cm−2, 3.60%) and THS electrode (13.20 mA cm−2, 5.48%), respectively.

A general precursor strategy for one-dimensional titania with surface nanoprotrusion and tunable structural hierarchy

The design of one-dimensional titania with tunable structural hierarchy holds exciting implications for applications such as optoelectronics, sensing and catalysis. Here, we report a general precursor strategy for one-dimensional titania with surface nanoprotrusion and tunable hierarchical structures realized via a titanate route using electrospun titania fibers as precursors. One-dimensional hierarchical hollow titanate (1D-HHT) was first fabricated under mild alkaline hydrothermal conditions from electrospun amorphous TiO2 precursors. The time-dependent evolution of 1D-HHT has been investigated in detail. The concerted effect of alkaline etching and Ostwald ripening is responsible for the surface nanoprotrusion and modulation of structural hierarchy. Anatase TiO2 with the same hierarchical structures can be obtained using controlled calcination. The as-fabricated one-dimensional titania with varying levels of structural hierarchy exhibits about 1.3–1.5 times higher power conversion efficiency than commercial P25 as a photoanode material for dye-sensitized solar cells (DSSCs). The current work may be extended for more functional TiO2-based materials with tunable structural hierarchy and could widen the application range of electrospinning technology for one-dimensional hierarchical structures.

Porous α-Fe2O3 microflowers: Synthesis, structure, and enhanced acetone sensing performances

Porous α-Fe2O3 microflowers, which were composed of many nanospindles assembled by large numbers of nanoparticles, were successfully synthesized by calcining the FeSO4(OH) precursor prepared through a simple ethanol-mediated method. Various techniques were employed to obtain the crystalline and morphological properties of the as-prepared products. The formation process of such microstructure was proposed according to the morphology and component of the products obtained at different reaction time. Moreover, the obtained α-Fe2O3 was utilized as sensing materials upon exposure to various test gases. As expected, in virtue of the less-agglomerated configuration and unique porous structure, the hierarchical α-Fe2O3 microflowers exhibited higher response as well as faster response/recovery time to acetone when compared with α-Fe2O3 nanoparticles. Significantly, the response time was measured to be 1s at the low operating temperature of 210°C.

Bilayered photoanode consisting of zinc oxide hollow spheres and urchin-like titanium dioxide microspheres enables fast electron transport and efficient light-harvesting for improved-performance dye-sensitized solar cells

Derived from ZnO hollow spheres (ZHSs) as the underlayer and urchin-like TiO2 spheres (UTSs) as the light scattering overlayer, a new bilayered photoanode (ZHS + UTS) is fabricated for use in dye-sensitized solar cells (DSSCs). The ZHSs which directly grow on FTO are synthesized via a one-pot hydrothermal method. The DSSC based on the ZHSs achieves an overall photoelectric conversion efficiency (PCE) of up to 4.84%, which is mainly ascribed to fast electron transport. On the other hand, three kinds of UTSs of different size and morphology are prepared by simply adjusting the titanium precursor dosage. The hierarchical UTSs composed of needle-like thin nanosheets have large specific surface areas, enabling sufficient dye adsorption. In particular, UTS-2 (synthesized using a TiCl3 volume of 0.6 mL) shows strong light-scattering ability and hence is further applied as a scattering layer in the bilayered photoanode. The ZHS + UTS-2 based DSSC finally achieves the highest photocurrent density (Jsc = 18.13 mA cm−2) and therefore an enhanced PCE of 8.67%. The improved photovoltaic performance is attributed to the synergic effects of the ZHSs and UTSs, i.e. the fast electron transport favored by the highly crystallized ZHSs leading to a reduced interfacial charge recombination, the efficient light scattering effect due to the novel morphology of the UTSs, and the sufficient dye adsorption ensured by the large specific surface areas of the ZHSs and UTSs.