Abstract2D materials, such as graphene, transition metal dichalcogenides, and black phosphorus, have become the most potential semiconductor materials in the field of optoelectronic devices due to their extraordinary properties. Owing to the layer‐dependent and appropriately sized bandgaps, photodetectors based on various 2D materials are designed and manufactured rationally. Utilizing the unique properties of 2D materials, many surprising physical phenomena of junctions based on 2D materials can be obtained after different 2D materials are stacked together. This makes heterojunctions more popular than 2D materials themselves, and the design of 2D materials for human beings is easier than ever. In this review, recent progress in optoelectronic applications based on 2D materials and their heterojunctions is summarized and discussed.
Hierarchical, mesoporous CuCo 2 O 4 nanograss has been synthesized on copper foam using a simple and cost-effective hydrothermal approach followed by a post-annealing treatment. The electrodes made from the novel nanoarchitecture exhibit multi-functional electrochemical performance. They deliver an excellent specific capacitance of 796 F g -1 at a current density of 2 A g -1 in a 2 M KOH aqueous solution and a long-term cyclic stability of 94.7% capacitance retention after 5000 cycles.When applied to electro-catalytic oxidation of methanol, the current density of the CuCo 2 O 4 /Cu foam electrode in 1 M KOH mixed with 0.5 M methanol is maintained up to 27.6 A g -1 . The superior electrochemical performances are mainly due to the unique one dimensional porous acicular architecture with very large surface area and 2 porosity grown on highly conductive Cu substrate, offering faster ion/electron transfer, an improved reactivity and an enhanced structural stability. The fabrication strategy presented here is simple, cost-effective and scalable, which can open new avenues for large-scale applications of the novel materials in energy storage.Fig. 5 (a, b) Low-magnification and high-magnification TEM images of an acicular CuCo 2 O 4 nanograss leaf; (c) corresponding SAED pattern; and (d) energy-dispersive X-ray spectrum of the elements Co, Cu and O.
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