Carbon Dots‐Decorated Carbon‐Based Metal‐Free Catalysts for Electrochemical Energy Storage

Abstract

In the past ten years, carbon dots‐decorated, carbon‐based, metal‐free catalysts (CDs‐C‐MFCs) have become the fastest‐growing branch in the metal‐free materials for energy storage field. However, the further development of CDs‐C‐MFCs needs to clear up the electronic transmission mechanism rather than primarily relying on trial‐and‐error approaches. This review presents systematically and comprehensively for the first time the latest advances of CDs‐C‐MFCs in supercapacitors and metal–air batteries. The structure–performance relationship of these materials is carefully discussed. It is indicated that carbon dots (CDs) can act as the electron‐rich regions in CDs‐C‐MFCs owing to their unique properties, such as quantum confinement effects, abundant defects, countless functional groups, etc. More importantly, specific doping can effectively modify the charge/spin distribution and then facilitate electron transfer. In addition, present challenges and future prospects of the CDs‐C‐MFCs are also given.

Synthesizing Red Fluorescent Carbon Dots from Rigid Polycyclic Conjugated Molecules: Dual‐Mode Sensing and Bioimaging in Biochemical Applications

“…The high‐resolution (HR) TEM images revealed that the lattice spacing of the R‐CDs was 0.18 nm (inset, Figure 1), which was consistent with the previously reported lattice spacing of sp 2 graphite, C (511). [ 52 ] This indicated the possible existence of a π‐conjugated skeleton of carbon networks in the CDs, confirmed by the Raman spectrum ( Figure a). The two peaks at 1282 cm −1 (D‐band) and 1385 cm −1 (G‐band) [ 35 ] in the spectrum corresponded to the regions of disorder or defects and the sp 2 carbon networks, respectively.…”

Carbon Dots as New Building Blocks for Electrochemical Energy Storage and Electrocatalysis

“…Heteroatom doping is one of the simplest and most effective methods, which can be easily realized by selecting the suitable precursor molecules when preparing CDs. [ 3 ] Due to the differences in electronegativity relative to carbon, doped heteroatoms (N, B, S, and P) always cause charge redistribution in neighboring carbon atoms, resulting in changes in the local electronic structure. [ 4a ] This can promote the adsorption of reactants and intermediates, and increase the intrinsic activity of active sites, thus benefiting electrochemical reactions.…”

“…Accordingly, the development of energy storage systems has become a crucial part of the transition from fossil fuels to renewable energy. [ 3 ] In addition, the increasing popularity of electric vehicles and portable electronic products creates the need for electrochemical energy storage devices with high energy densities and long‐term stability. [ 4 ] Supercapacitors and rechargeable batteries represent key energy storage systems for these applications owing to their safety, low price, and high efficiency.…”

“…The development of novel electrodes for electrochemical devices has become a priority of global research in chemistry, engineering, and materials science. [ 3,4 ] Whilst the working principles of batteries, supercapacitors, electrolyzers, and fuel cells are all different, their operation and ultimately commercial viability and scalability rely on advanced electrode materials, which ideally should possess high electrochemical activity (i.e., intrinsic activity and a high electrochemical surface area), excellent physical properties (i.e., good electronic and ionic conductivities, chemical, and mechanical robustness) and be based on earth abundant elements (thereby enabling large scale manufacture and low device costs).…”

“…Such fluorescent carbon nanomaterials were subsequently classified as 0D carbon dots (CDs), to distinguish them from other forms of carbon nanomaterials. [ 3,9 ] The structure of CDs usually consists of a core composed of sp 2 /sp 3 hybrid carbon atoms and an amorphous shell with plentiful O/N‐containing functional groups or polymer chains. [ 10,11 ] According to the micro‐structure of carbon cores, CDs are further divided into graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs) and carbonized polymer dots (CPDs) ( Figure 1 ).…”