A challenging but pressing task to design and synthesize novel, efficient, and robust pH‐universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production ...through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru‐M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH‐universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm−2 in 1 m KOH, 0.5 m H2SO4, and 1 m PBS, respectively, for Ru loading at 5.93 μgRu cm−2. This performance is among the best catalytic activities reported for any platinum‐free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity.
How low can Ru go: A scalable and general synthetic method for the preparation of transition‐metal‐doped RuM/carbon quantum dots (CQDs; M=Ni, Mn, Cu) has been developed through metal‐mediated CQD condensation and carbonization. The low‐ruthenium‐content RuM/CQD catalysts exhibit outstanding activity and stability in catalyzing hydrogen evolution at all pH values.
A facile, low-cost, green, kilogram-scale synthesis of high quality CQDs were synthesized. The throughput of CQDs is 1.4975 kg in one pot and the as-prepared CQDs have a highly crystalline hexagonal ...structure with remarkable solubility, stability, and biocompatibility. It showed outstanding electrocatalytic activity, Fe3+ sensitivity and good biocompatibility.
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The development of large-scale synthetic methods for high quality carbon quantum dots (CQDs) is fundamental to their applications. However, the macroscopic preparation and scale up synthetic of CQDs is still in its infancy. Here, we report a facile, green, kilogram-scale synthesis of high quality fluorescent CQDs derived from poplar leaves via a one-step hydrothermal method. Notably, the throughput of CQDs can reach a level up to as high as 1.4975 kg in one pot. The structure and properties of the as-prepared CQDs were assessed through TEM, XRD, XPS and various spectroscopic methods. The obtained high quality CQDs with a photoluminescent quantum yield of 10.64% showed remarkable stability in aqueous media, rich functional groups, high photostability, consistent photoluminescence within biological pH range and low cytotoxicity. On account of these good properties, we demonstrated the multifunctional application to electrocatalytic water splitting, Fe3+ sensing and bioimaging. It showed remarkable electrocatalytic activity, Fe3+ sensitivity and good biocompatibility. This study provides a green, facile, inexpensive and large-scale method for producing high quality CQDs, which provides application value for large-scale production of CQDs.
Highly active, stable, and cheap Pt‐free catalysts for the hydrogen evolution reaction (HER) are facing increasing demand as a result of their potential use in future energy‐conversion systems. ...However, the development of HER electrocatalysts with Pt‐like or even superior activity, in particular ones that can function under alkaline conditions, remains a significant challenge. Here, the synthesis of a novel carbon‐loaded ruthenium nanoparticle electrocatalyst (Ru@CQDs) for the HER, using carbon quantum dots (CQDs), is reported. Electrochemical tests reveal that, even under extremely alkaline conditions (1 m KOH), the as‐formed Ru@CQDs exhibits excellent catalytic behavior with an onset overpotential of 0 mV, a Tafel slope of 47 mV decade−1, and good durability. Most importantly, it only requires an overpotential of 10 mV to achieve the current density of 10 mA cm−2. Such catalytic characteristics are superior to the current commercial Pt/C and most noble metals, non‐noble metals, and nonmetallic catalysts under basic conditions. These findings open a new field for the application of CQDs and add to the growing family of metal@CQDs with high HER performance.
The ruthenium@carbon quantum dots (Ru@CQDs) electrocatalyst is very robust for the hydrogen evolution reaction in alkaline media, with an onset overpotential of 0 mV and low overpotentials at 10 mA cm−2 (10 mV). More importantly, after 10 000 cycles, the current density at 10 mA cm−2 of the Ru@CQDs catalyst increases merely 4 mV at 10 mA cm−2.
Carbon dots (CDs) have received much attention due to their superior properties including water solubility, low toxicity, biocompatibility, small size, fluorescence, and ease of modification. The use ...of a more environmentally friendly method to prepare high‐quality CDs is still an urgent question waiting for solve. The use of renewable, inexpensive, and green biomass resources not only meets the urgent need for large‐scale synthesis biomass CDs (BCDs), but also promotes the development of sustainable applications. In this article, we summarize the representative methods for synthesizing BCDs in green and simple ways using biomass as a carbon source, including hydrothermal carbonization, and microwave, pyrolysis. The prepared BCDs have a uniform particle size distribution and a relatively high throughput, which provide a method to scale up industrial production. Moreover, the integration of specific optical properties, that is, tunable photoluminescence and up‐photoluminescence, has led to remarkable use in bioimaging, sensing, and drug delivery. But the current review is not particularly comprehensive for BCDs. Therefore, we now provide a review focusing on the synthesis, properties, and recent advances in BCDs in biosensing, bioimaging, optoelectronics, and catalytic applications.
In this manuscript, the synthesis methods of BCDs prepared with biomass as a carbon source are introduced, and their properties and applications in various aspects are introduced. In this diagram reflects the properties and applications of BCDs.
Sodium ion batteries have drawn extensive attentions for large-scale energy storage to replace lithium ion batteries primarily due to the natural abundance of sodium resource and low cost, but their ...energy density and electrochemical performance are hindered by the sluggish diffusion kinetics of sodium ion. Herein, free-standing nitrogen-doped graphene aerogel has been fabricated via hydrothermal reaction as the potential anode material for sodium ion batteries. The three dimensional porous network structure of the graphene aerogel provides sufficient interstitial space for sodium ion accommodation, allowing fast and reversible ion intercalation/de-intercalation. The nitrogen doping could introduce defects on the graphene sheets, making the feasible transport of large-sized sodium ion. Benefiting from the effective structure and nitrogen doping, the obtained material demonstrates high reversible capacities, good cycling performance (287.9 mA h g
after 200 cycles at a current density of 100 mA g
), especially superior rate capability (151.9 mA h g
at a high current density of 5 A g
).
Silicon has been identified as a highly promising anode for next-generation lithium-ion batteries (LIBs). The key challenge for Si anodes is large volume change during the lithiation/delithiation ...cycle that results in chemomechanical degradation and subsequent rapid capacity fading. Here we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. On charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward Li breathing with negligible particle-level outward expansion. Our mechanics analysis revealed that such inward expansion is enabled by the much stiffer lithiated layer than the unlithiated porous layer. LIBs assembled with the hp-SiNSs exhibit high capacity, high power and long cycle life, which is superior to the current commercial Si-based anode materials. The low-cost synthesis approach provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.
A three dimensional (3D) nanostructured composite based on the self-assembly of MoS2 nanospheres and polyaniline (PANI) loaded on reduced graphene oxide (denoted by 3D MoS2-PANI/rGO) was prepared via ...a feasible one-pot hydrothermal process. The 3D MoS2-PANI/rGO nanocomposite not only exhibits good functionality and bioaffinity but also displays high electrochemical catalytic activity. As such, the developed 3D MoS2-PANI/rGO nanocomposite can be employed as the sensing platform for simultaneously detecting small biomolecules, i.e., ascorbic acid (AA), dopamine (DA), and uric acid (UA). The peak currents obtained from the differential pulse voltammetry (DPV) measurements depended linearly on the concentrations in the wide range from 50 μM to 8.0 mM, 5.0 to 500 μM, and 1.0 to 500 μM, giving low detection limits of 22.20, 0.70, and 0.36 μM for AA, DA, and UA, respectively. Furthermore, the 3D MoS2-PANI/rGO-based electrochemical sensor also exhibited high selectivity, good reproducibility and stability toward small molecule detection. The present sensing strategy based on 3D MoS2-PANI/rGO suggests a good reliability in the trace determination of electroactive biomolecules.
Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (≈3600 mAh g–1). However, the huge volume swelling and shrinking during cycling, which ...mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic efficiency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well‐developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response at electrode level. For the first time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle efficiency. In situ transmission electron microscopy and finite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion.
Si–C yolk–shell is applied to regulate the breathing effect and one order of magnitude of reduction on thickness changes at the electrode level during cycling is achieved: the electrode thickness variation reduces down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials.
A recently created class of inorganic 2D materials, MXenes, has become a subject of intensive research. Reducing their dimensionality from 2D to 0D quantum dots (QDs) could result in extremely useful ...properties and functions. However, this type of research is scarce, and the reported Ti3C2 MXene QDs (MQDs) have only shown blue fluorescence emission. This work demonstrates a facile, high‐output method for preparing bright white emitting Ti3C2 MQDs. The resulting product is two layers thick with a lateral dimension of 13.1 nm. Importantly, the as prepared Ti3C2 MQDs present strong two‐photon white fluorescence. Their fluorescence under high pressure is also investigated and it is found that the white emission is very stable and the pressure makes it possible to change from cool white emission to warm white emission. Hybrid nanocomposites are then fabricated by polymerizing Ti3C2 MQDs in polydimethylsiloxane (PDMS) solution, and the bright white emitting hybrid materials in white light‐emitting diodes are used. This work provides a facile and general approach to modulate various nanoscale MXene materials, and could further aid the wide development of applications for MXene materials in various optical‐related fields.
A facile, high‐output method for the fabrication of Ti3C2 MXene quantum dots (MQDs) with direct white photoluminescence and two‐photon fluorescence is unprecedentedly designed. High‐pressure studies of Ti3C2 MQDs are also performed, demonstrating a stable white emission that changes from cool white emission to warm white emission. The work paves a general way to achieve nanoscale MXene materials with enhanced applications in various optical‐related fields.
In this study, the calcium gangue material calcite (−10 μm) was used to investigate the effects of different kinds of metal ions and dosages on the dispersion behavior of calcite. The test results ...showed that the dispersion behavior of calcite was poor under strongly alkaline conditions without the addition of metal ions, and the reason for that was calcite dissolved ions. The degree of influence of different metal ions on calcite dispersion behavior was Fe3+ > Mg2+ > Na+. The three metal ion dosage tests showed that the dispersion behavior of calcite became poorer with the increase of metal ion dosage. This mainly showed that with the increase of Na+ dosage, the trend of the dispersion behavior of calcite was not obvious, but with the increase of Fe3+ and Mg2+ dosage, the trend of calcite dispersion behavior changed more. The dispersion behavior of calcite was devastated by 5 × 10−4 mol/L Fe3+ at pH = 4−12. The different mechanisms of the three metal ions were identified by zeta potential, solution chemistry, and XPS analysis. Na+ only changed the zeta potential value of the calcite surface, which acted as a compressed electric double layer. However, the formation of metal hydroxide species or metal hydroxide surface precipitation due to the adsorption of Fe3+ and Mg2+ on the mineral surface resulted in the change of the dispersion behavior of calcite.
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