Luminescent carbon quantum dots (CQDs) represent a new form of nanocarbon materials which have gained widespread attention in recent years, especially in chemical sensor, bioimaging, nanomedicine, solar cells, light-emitting diode (LED), and electrocatalysis. CQDs can be prepared simply and inexpensively by multiple techniques, such as the arc-discharge method, microwave pyrolysis, hydrothermal method, and electrochemical synthesis. CQDs show excellent physical and chemical properties like high crystallization, good dispersibility, photoluminescence properties. In particular, the small size, superconductivity, and rapid electron transfer of CQDs endow the CQDs-based composite with improved electric conductivity and catalytic activity. Besides, CQDs have abundant functional groups on the surface which could facilitate the preparation of multi-component electrical active catalysts. The interactions inside these multi-component catalysts may further enhance the catalytic performance by promoting charge transfer which plays an important role in electrochemistry. Most recent researches on CQDs have focused on their fluorescence characteristics and photocatalytic properties. This review will summarize the primary advances of CQDs in the synthetic methods, excellent physical and electronic properties, and application in electrocatalysis, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reduction (HER), and CO₂ reduction reaction (CO₂RR).

The rational design and development of cost-effective and high-efficiency bifunctional electrocatalysts for overall water splitting is of prime significance for advancing large-scale commercial hydrogen production. Herein, a novel nanoporous NiAl layered double hydroxide nanosheet array with optimized Ni active sites on nickel foam (np-NiAl-LDH/NF) is prepared by a facile and simple metal-defect engineering strategy. We demonstrate that the partial leaking of catalytically inactive Al sites in NiAl-LDH nanosheets during anodic electrochemical etching can not only trigger the generation of a nanoporous structure and electron-rich Ni²⁺ sites, but can also increase the content of Ni³⁺ active sites accompanied by abundant oxygen defects, resulting in the synchronously increased density and intrinsic activity of Ni active sites and also enhanced mass and electron transport, thus greatly promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. As expected, the as-obtained np-NiAl-LDH/NF electrode needs extremely small overpotentials of 90 and 180 mV to deliver the 10 mA cm⁻² current density for the HER and OER in alkaline media, respectively. Moreover, an alkaline electrolyzer assembled with np-NiAl-LDH/NF functioning as both the anode and cathode can yield 10 and 100 mA cm⁻² at quite low voltages of ∼1.5 and 1.7 V, respectively, far outperforming the Pt/C/NF–IrO₂/NF-coupled electrolyzer, and can give durable stability for at least 60 h. This work provides new insights for creating highly efficient Ni-based electrocatalysts toward overall water splitting via engineering on catalytically active Ni sites.

A kind of hierarchical porous magnetic Fe₂O₃@AlO(OH) superstructure nanomaterial was prepared by a facile method involving ethylene glycol as both cross linker and stabilizing agent. The resulting hierarchical material shows ultrafast adsorption rates and high adsorption capacities for removal of Pb(II), As(V) and Cr(VI) ions from aqueous solution.