Newborn 2D materials for flexible energy conversion and storage

Abstract

Newborntwo-dimensional materials (NB2DMs) beyond graphene such as transition metal dichalcogenides (TMDs) exhibit excellent optoelectronic and mechanical properties as well as high theoretical specific capacity, which make them become the promising building blocks of flexible energy devices related to energy conversion and storage. Compared to graphene with zero band gap or traditional friable materials such as Si, these NB2DMs are more suitable to construct flexible devices as active layers of optoelectronic devices or as active materials for batteries. The present review focuses on the recent advances in bendable energy devices based on NB2DMs, including batteries, supercapacitors (SCs), solar cells, photodetectors and nanogenerators (NGs). The NB2DMs pave a new way to construct next-generation flexible energy devices with improved performance and we believe that those devices will be seen in our daily life and change our lifestyle in the immediate future.

Reduced-sized monolayer carbon nitride nanosheets for highly improved photoresponse for cell imaging and photocatalysis

“…Due to the fascinating physicochemical and electronic properties arising from the small dimensions and quantum confinement effects (QCE) [1][2][3], ultrathin nanosheets have been the focus of substantial research in the light of fundamental studies and their broad applications in various fields, including optoelectronic devices [4], energy conversion and storage [5], sensors [6][7][8][9], biomedicine [10], and catalysis [11][12][13][14][15]. In particular, polymeric graphitic carbon nitride nanosheets (GCNNs), an n-type semiconductor, have been receiving considerable attention due to their many intriguing advantages such as the fact that they contain no metal, and nontoxicity, easy availability, sensitive photo-response, excellent chemical and thermal stability, and unique electronic structures [16][17][18][19].…”

Strategies for designing metal oxide nanostructures

“…Free-standing ultrathin 2D nanostructures are highly desirable for obtaining superior catalytic, photovoltaic, and electrochemical performances, due to their large surface-tovolume ratios and confined thickness on the atomic scale [152][153][154][155][156][157][158][159][160][161][162]. Strictly speaking, materials with few-layered atomic planes and 2D scalability should be called "2D crystals", which can also be called as "ultrathin nanosheets" due to their appearance [163].…”

“…Strictly speaking, materials with few-layered atomic planes and 2D scalability should be called "2D crystals", which can also be called as "ultrathin nanosheets" due to their appearance [163]. For example, the 2D carbon network-graphene-features extremely high carrier mobility, mechanical flexibility, optical transparency, and chemical stability, which provides a great opportunity for developing new electronic materials, novel sensors and metrology facilities, and superior energy conversion and storage devices [152][153][154][155][156]. Compared to the widely studied graphene and dichalcogenides, the ultrathin 2D transition metal oxide nanosheets have been relatively rarely studied, owing to the difficulties in the preparation of high quality 2D metal oxide nanomaterials.…”

“…At present, there are mainly three approaches to the fabrication of 2D metal oxide nanosheets, namely, liquid/chemical exfoliation of layered host materials, CVD growth, and wet-chemical self-assembly, as in the schematic illustration shown in Figs 4a-d [152][153][154][155][156][157][158][159][160][161][162][163]. Both the former two approaches start from bulk layered host materials to obtain low-dimensional nanomaterials; we usually call them forms of "top-down" synthesis.…”

Defective MoS2 electrocatalyst for highly efficient hydrogen evolution through a simple ball-milling method

“…These cumulate sandwiched S-Mo-S layers are held together by van der Waals force and piled in a graphite-like structure to form bulk material [19]. Up to now, many efforts have been made to improve the performance of MoS 2 as HER catalysts [20][21][22][23][24]. There are two strategies to optimize the electrochemical performance of MoS 2 including revealing active sites and increasing the electrical conduction for improving the electron transfer [25,26].…”