Xianpei Ren

One-step hydrothermal synthesis of monolayer MoS2 quantum dots for highly efficient electrocatalytic hydrogen evolution

Designing MoS2 nanocatalysts with ultrasmall size and few layers is an effective strategy to enhance their electrocatalytic activity in the hydrogen evolution reaction (HER). In this work, uniform MoS2 quantum dots (QDs) are synthesized by a novel and facile hydrothermal route. Transmission electron microscopy and atomic force microscopy measurements show that the resulting products possess a monolayer thickness with an average size of about 3.6 nm. Benefiting from the abundance of exposed catalytic edge sites, as well as the excellent intrinsic conductivity of the monolayer structure, the MoS2 QDs showed excellent catalytic activity with a low overpotential of approximately 160 mV and a small Tafel slope of 59 mV dec−1, which made it a promising HER electrocatalyst for practical applications.

Ag Nanoparticle-Sensitized WO3 Hollow Nanosphere for Localized Surface Plasmon Enhanced Gas Sensors

Ag nanoparticle (NP)-sensitized WO3 hollow nanospheres (Ag-WO3-HNSs) are fabricated via a simple sonochemical synthesis route. It is found that the Ag-WO3-HNS shows remarkable performance in gas sensors. Field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images reveal that the Agx-WO3 adopts the HNS structure in which WO3 forms the outer shell framework and the Ag NPs are grown on the inner wall of the WO3 hollow sphere. The size of the Ag NPs can be controlled by adjusting the addition amount of WCl6 during the reaction. The sensor Agx-WO3 exhibits extremely high sensitivity and selectivity toward alcohol vapor. In particular, the Ag(15nm)-WO3 sensor shows significantly lower operating temperature (230 °C), superior detection limits as low as 0.09 ppb, and faster response (7 s). Light illumination was found to boost the sensor performance effectively, especially at 405 and 900 nm, where the light wavelength resonates with the absorption of Ag NPs and the surface oxygen vacancies of WO3, respectively. The improved sensor performance is attributed to the localized surface plasmon resonance (LSPR) effect.

Solar-to-Hydrogen Efficiency of 9.5 % by using a Thin-Layer Platinum Catalyst and Commercial Amorphous Silicon Solar Cells

A photoelectrochemical system was set up with commercial triple‐junction solar cells to split water into hydrogen. To minimize the Pt loading and material cost and to maintain a high catalytic activity, a thin Pt layer on a high‐surface‐area Ni foam was used to catalyze the hydrogen evolution reaction. The solar‐to‐hydrogen efficiency measured from the hydrogen gas evolved is as high as 9.5 %.

Band alignment of TiO2/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

The energy band alignment between pulsed-laser-deposited TiO2 and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO) of 0.61 eV and a conduction band offset (CBO) of 0.29 eV were obtained across the TiO2/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction.