Yanchao Mao

Oxygen vacancies promoting photoelectrochemical performance of In 2 O 3 nanocubes

This work reports a facile method for preparing the new photoactive In2O3 films as well as their implementation in photoelectrochemical (PEC) application. We firstly investigated the relationship between oxygen vacancies (VO) and PEC performance and revealed a rule between them. We found that the optimized In2O3−n sample yielded a photocurrent density up to 3.83 mA/cm2 in 1 M Na2SO4 solution under the solar illumination. It also gave efficiency as high as 75% over 400 nm in the incident-photon-to-current-conversion efficiency (IPCE) spectrum, which is the best value for an In2O3 photoanode reported. Moreover, the PEC performance of these films is enhanced as the VO increased and then decreased with further increasing VO. This two-side effect means VO can favor the photoelectron activation, or act as recombination centers to prohibit the generation of photocurrent. Making highly photoactive In2O3 nanostructures in this work will open up new opportunities in various areas.

Hydrothermal growth of SnS2 hollow spheres and their electrochemical properties

SnS2 hollow microspheres and SnS2 3D nanoflake-based hollow microspheres are successfully synthesized via a one-step hydrothermal process. From the experimental results, a mechanism based on bubble-templating, self-assembling and subsequent shell evolution was proposed. These hollow spheres were tested as anode materials in lithium ion batteries (LIBs) and found to have good cycling performance. This article provide a facile strategy to prepare hollow structures and give some insight studies on their applications in lithium ion storage and retrieval.

Vertically aligned In2O3 nanorods on FTO substrates for photoelectrochemical applications

Vertically aligned In2O3 nanorod arrays (NRAs) were obtained by annealing the as-prepared In(OH)3 precursors that grew directly on FTO substrates via a simple template-free electrochemical assembly process. The absorption edges of In2O3 NRAs show a red-shift to the visible region, and a remarkable photocurrent response under visible light illumination (λ ≥ 390 nm) in photoelectrochemical cells.

Room-temperature ferromagnetism in hierarchically branched MoO3 nanostructures

Hierarchically branched MoO3 nanostructures on Ti substrates were successfully prepared via a simple and controllable electrodeposition–heat-treatment method. XPS and Raman results indicate that these branched MoO3 nanostructures possess some oxygen vacancies. The magnetic measurements show the prepared branched MoO3 nanostructures exhibit ferromagnetic behaviour at room temperature. The observed room-temperature ferromagnetism can be mainly ascribed to the oxygen vacancies on the surface of the samples.

Facile synthesis of CuO nanorods with abundant adsorbed oxygen concomitant with high surface oxidation states for CO oxidation

Oxygen adsorption materials play an important role in catalysis. However, the conventional catalytic mechanism of CO oxidation over copper oxide-based catalysts is based on lattice-oxygen oxidation processes, which neglects the significance of the oxidizability of the copper component and the adsorbed oxygen. Herein, we propose that poorly-crystallized CuO nanorods are capable of adsorbing abundant oxygen along with increasing the Cu oxidation states to close to 3+, meaning that CO catalytic oxidation occurs directly on the adsorbed oxygen and that Cu oxidation states do not fall to 1+ during catalytic reactions. The rate-controlled step is the surface oxidizability of the CuO nanorods, which increases with increasing temperature and oxidizability of the environment involved. These catalytic processes are distinctly different from the conventional case. The unique oxygen adsorption and catalytic properties of the CuO nanorods originate from the increasing trend in Cu oxidation state in the p-type CuO, enhanced by the defect structures and coarse surfaces of the sample. Such structure and morphology characteristics are closely related to the liquid membrane growing environment, which induces poor crystallization of the nanorods. The characterization methods include scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transformation infrared spectroscopy (FTIR).

ZnO/SnO2 hierarchical and flower-like nanostructures: facile synthesis, formation mechanism, and optical and magnetic properties

Hierarchical and flower-like nanostructures with ZnO backbones and SnO2 branches were successfully prepared by electrodeposition (for ZnO nanorod arrays) and hydrothermal growth (for SnO2). The SnO2 nanorods grew epitaxially on the sides of ZnO nanorods. The morphologies and surface areas of ZnO/SnO2 hierarchical nanostructures can be tailored by changing the reaction time. Such hybrid ZnO/SnO2 nanostructures were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectrophotometry and by using an accelerated surface area and porosimetry system (ASAP 2020M). A possible formation process and growth mechanisms for such hybrid ZnO/SnO2 nanostructures has been proposed based on series of time-dependent experiments. The UV properties show an enhanced as near-band gap emission compared with the primary ZnO nanorods. In addition, the magnetic properties of hierarchical ZnO/SnO2 nanostructures were also studied.

Negative thermal expansion and broad band photoluminescence in a novel material of ZrScMo2VO12.

In this paper, we present a novel material with the formula of ZrScMo2VO12 for the first time. It was demonstrated that this material exhibits not only excellent negative thermal expansion (NTE) property over a wide temperature range (at least from 150 to 823 K), but also very intense photoluminescence covering the entire visible region. Structure analysis shows that ZrScMo2VO12 has an orthorhombic structure with the space group Pbcn (No. 60) at room temperature. A phase transition from monoclinic to orthorhombic structure between 70 and 90 K is also revealed. The intense white light emission is tentatively attributed to the n- and p-type like co-doping effect which creates not only the donor- and acceptor-like states in the band gap, but also donor-acceptor pairs and even bound exciton complexes. The excellent NTE property integrated with the intense white-light emission implies a potential application of this material in light emitting diode and other photoelectric devices.

Electrochemical synthesis of CoFe2O4 porous nanosheets for visible light driven photoelectrochemical applications

CoFe2O4 porous nanosheets (CFOPNSs) on F-doped SnO2 coated glass (FTO) substrates with 30.5 nm average pore diameter were prepared through a template-free electrochemical method from aqueous solution. The CFOPNSs exhibit obvious absorption in the visible-near infrared light range, and obvious photocurrent responses under visible light illumination (λ ≥ 390 nm). Additionally, XPS and Raman results indicate that the valence band maximum (VBM) of the CFOPNSs occurs at the Co 3d level.

Controllable electrochemical synthesis of CoFe2O4 nanostructures on FTO substrate and their magnetic properties

CoFe2O4 nanosheets (NSs) and nanoparticles (NPs) were successfully synthesized on F-doped SnO2 coated glass (FTO) substrate via a facile and controllable electrodeposition method. X-Ray photoelectron spectroscopy (XPS) results indicated that the CoFe2O4 NSs and NPs have different distributions of Co and Fe cations over tetrahedral and octahedral sites. The magnetic measurements showed that the prepared CoFe2O4 NSs exhibit higher value of magnetic properties, which can be mainly ascribed to the variation of the cation distribution.

Single-electrode triboelectric nanogenerators based on sponge-like porous PTFE thin films for mechanical energy harvesting and self-powered electronics

Triboelectric nanogenerators (TENGs) are promising innovative energy conversion devices that convert mechanical energy into electricity based on triboelectric friction. In this paper, we report the development of a single-electrode TENG (S-TENG) based on sponge-like porous polytetrafluoroethylene (PTFE) thin films. The porous PTFE thin films were fabricated via a facile approach by using deionized (DI) water as the soft template. The porosity effect on the output performance of the porous PTFE S-TENG was investigated under mechanical oscillations. The optimal porosity for achieving the maximum VOC output was found to be 5.1 V when the DI water volume fraction was 50%. The output voltage of the porous PTFE S-TENG is 1.8 times higher than that of the solid PTFE thin film based S-TENG under the same oscillation. The porous PTFE S-TENG can also generate considerable electricity by harvesting mechanical energy from human motions. An output voltage of 1.1 V was obtained when the S-TENG was pressed by a bare human hand. When pressed by a human hand within a latex glove, the output voltage reached 6.9 V, and the generated electric energy could instantaneously power 5 commercial green light emitting diodes (LEDs) without any energy storage process. This development of the porous PTFE S-TENG could open a new avenue towards developing self-powered personal electronics, owing to its flexibility, simple one-electrode structure, and ability to harvest mechanical energy from human motions.