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).

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A Mini Review on Carbon Quantum Dots: Preparation, Properties, and Electrocatalytic Application.

Surface and interface engineering of noble-metal-free electrocatalysts for efficient overall water splitting

Electrochemical water splitting has a promising future in producing high-density and green hydrogen, however, the sluggish H2O dissociation process, due to the low H2O adsorption on the catalyst surface, greatly hinders the industrial electrochemical water splitting on a large scale. Therefore, intensive efforts have been devoted to the exploration of efficient approaches for fabricating highly efficient electrocatalysts with appropriate H2O adsorption, such as defect engineering, interface engineering, and morphology design. Among them, metal doping, particularly noble metal (Ru, Rh, and Ir) doping, is essential to optimize the adsorption of reaction intermediates on the surface of catalysts, and has thus attracted increasing research interest. In order to uncover the significant role of noble metal doping in boosting water splitting electrocatalysis, this minireview showcases the most recent examples towards this endeavor, and begins by illustrating the mechanisms for water splitting and several advanced approaches for realizing noble metal doping. In the main text, we have also specifically highlighted the influences of noble metal doping on the electrocatalytic performance. Finally, some challenges and future outlooks are also presented to offer guidance for practical applications.

Advances in noble metal (Ru, Rh, and Ir) doping for boosting water splitting electrocatalysis

The effective pre-treatment methods are required for the destruction of the complex biomass structure to economically produce high grade fuels and valuable platform chemicals. Ionic liquids have high potential for energy efficient biomass pre-treatment due to their low vapour pressure, emission profile, recyclability and tuneable properties; some ionic liquids can even be prepared from renewable biomass feedstocks. However, a number of issues currently impede the large scale uptake of ionic liquids including their cost of production, detailed understanding the macro, micro and molecular level deconstruction mechanisms which inhibits process optimisation and modelling, and the need for techno-economic astable sessment on large scale trials. So far, laboratory to bench scale IL pre-treatments of various lignocellulosic biomasses were studied by changing various process parameters where the aims were to investigate the biomass dissolution mechanism and understand the pre-treatment performance of ILs. This review outlines current research gaps and potential applications for ionic liquids in the destruction of biomass into its components followed by separation of lignin, hemicellulose and cellulose rich fractions.

Progress on the pre-treatment of lignocellulosic biomass employing ionic liquids

Supports promote single-atom catalysts toward advanced electrocatalysis

Ternary FeCoNi alloy nanoparticles embedded in N-doped carbon nanotubes for efficient oxygen evolution reaction electrocatalysis

Tuning the electronic state of a nanocatalyst is of vital importance for elevating its catalytic performance toward oxygen evolution reaction (OER). Herein, a cation-anion dual doping strategy has been proposed for modifying the electronic structure of CoP via doping Fe and S atoms. Impressively, Fe doping has been demonstrated to be favorable for improving the carrier density of CoP to produce more hydroxyl radicals (•OH), while S doping can further modify the electronic structure of CoP to improve the charge-transfer characteristics, thereby synergistically decreasing the energy barrier for the transformation of O* to OOH* and promoting the electrocatalytic OER performance. More importantly, the highly open nanobox structure is also beneficial for the exposure of more accessible catalytically active sites, which can substantially facilitate the electron and mass transport, leading to the superb catalytic OER performance. The successful modulation of OER performance via dual-doping strategy will pose a new strategy for designing more advanced nanocatalysts for energy-related catalysis process.

Cation-Anion Dual Doping Modifying Electronic Structure of Hollow CoP Nanoboxes for Enhanced Water Oxidation Electrocatalysis.

Although transition metal materials are extensively studied for hydrogen evolution reaction (HER) because of their intrinsic electrochemical properties, their practical applications have been hinde...

Carbon Quantum Dots Modulated NiMoP Hollow Nanopetals as Efficient Electrocatalysts for Hydrogen Evolution

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H2O2-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co9Se8@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co9Se8@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm-2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm-2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.

Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe.

Covalent organic frameworks are unique for their highly open architecture and attractive for use as promising gas adsorption and storage carriers. In this work, density functional theory calculations have been performed to investigate the properties of metal-doped covalent organic frameworks and their interactions with the SO2 gas molecule. It is found that a single metal atom (including Li, Na, K, and Sc) doped at the top of phenyls within the tetra(4-dihydroxyborylphenyl) silane (TBPS) building block of covalent organic frameworks can easily lose its valence electrons and can be positively charged. The SO2 gas molecule could be stably absorbed onto the metal-doped covalent organic frameworks. The absorbed SO2 molecule interacts with Li, Na, K, and Sc metal-doped covalent organic frameworks by the dominant donor-acceptor delocalization between 1-center lone pair of an oxygen atom within SO2 and 1-center non-Lewis lone pairs of the doped metal atom.

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Ju Wang

Papers

Ternary FeCoNi alloy nanoparticles embedded in N-doped carbon nanotubes for efficient oxygen evolution reaction electrocatalysis

Cation-Anion Dual Doping Modifying Electronic Structure of Hollow CoP Nanoboxes for Enhanced Water Oxidation Electrocatalysis.

Carbon Quantum Dots Modulated NiMoP Hollow Nanopetals as Efficient Electrocatalysts for Hydrogen Evolution

Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe.

Properties of Metal-Doped Covalent Organic Frameworks and Their Interactions with Sulfur Dioxide