RESUMO
Owing to rapid property degradation after ambient exposure and incompatibility with conventional device fabrication process, electrical transport measurements on air-sensitive 2D materials have always been a big issue. Here, for the first time, a facile one-step polymer-encapsulated electrode transfer (PEET) method applicable for fragile 2D materials is developed, which showed great advantages of damage-free electrodes patterning and in situ polymer encapsulation preventing from H2 O/O2 exposure during the whole electrical measurements process. The ultrathin SmTe2 metals grown by chemical vapor deposition (CVD) are chosen as the prototypical air-sensitive 2D crystals for their poor air-stability, which will become highly insulating when fabricated by conventional lithographic techniques. Nevertheless, the intrinsic electrical properties of CVD-grown SmTe2 nanosheets can be readily investigated by the PEET method instead, showing ultralow contact resistance and high signal/noise ratio. The PEET method can be applicable to other fragile ultrathin magnetic materials, such as (Mn,Cr)Te, to investigate their intrinsic electrical/magnetic properties.
RESUMO
Apart from active metals, supports also contribute significantly to the catalytic performance of supported metal catalysts. On account of the formed strain and defects, the heterostructured surface of the support may play a crucial role to activate the reactant molecules, while it is usually neglected. In this work, the Pt/γ-Mo2N catalyst was prepared via a facile solution method. This Pt/γ-Mo2N catalyst showed excellent activity and stability for catalyzing the water-gas shift (WGS) reaction. The reaction rates at 240 °C were 16.5 molCO molPt-1s-1 in product-free gas and 5.36 molCO molPt-1 s-1 in full reformate gas, which were almost 20 times that of the catalysts reported. It is found that the molybdenum species in the surface of the Pt/γ-Mo2N catalyst is molybdenum oxide as MoO3. This surface MoO3 is very easily reduced even at room temperature, and it transformed into highly distorted MoOx (2 < x < 3) in the WGS reaction. The MoOx on the catalyst surface greatly enhanced the capability of generating active oxygen vacancies to dissociate H2O molecules, which induced unexpectedly superior catalytic performance. Therefore, the intrinsically active surface in the Pt/γ-Mo2N catalyst for the WGS reaction was molybdenum oxide as MoOx (2 < x < 3).
RESUMO
As star material, perovskites have been widely used in the fields of optics, photovoltaics, electronics, magnetics, catalysis, sensing, etc. However, some inherent shortcomings, such as low efficiency (power conversion efficiency, external quantum efficiency, etc.) and poor stability (against water, oxygen, ultraviolet light, etc.), limit their practical applications. Downsizing the materials into nanostructures and incorporating rare earth (RE) ions are effective means to improve their properties and broaden their applications. This review will systematically summarize the key points in the design, synthesis, property improvements and application expansion of RE-containing (including both RE-based and RE-doped) halide and oxide perovskite nanomaterials (PNMs). The critical factors of incorporating RE elements into different perovskite structures and the rational design of functional materials will be discussed in detail. The advantages and disadvantages of different synthesis methods for PNMs will be reviewed. This paper will also summarize some practical experiences in selecting suitable RE elements and designing multi-functional materials according to the mechanisms and principles of REs promoting the properties of perovskites. At the end of this review, we will provide an outlook on the opportunities and challenges of RE-containing PNMs in various fields.
