Deep eutectic solvents (DESs), as a green alternative technology, exhibit great potential to recycle valuable elements from spent lithium-ion batteries (LIBs). However, due to the weak reducing power ...of DESs, raising the temperature and extending the duration of processing are not efficient for screening suitable DESs for the recycling of LIBs. Here, we propose a novel, simple and robust experimental method to identify suitable DESs for recycling spent LIBs. Based on electrochemical principles, the method proposed in this study can be used to quickly determine the reducing power of DESs. As an example, a choline chloride (ChCl) and urea mixture as a DES was found to possess strong reducing power, with a Li and Co extraction efficiency of 95% from spent LIBs obtained at a reduced reaction temperature of 180 °C and reaction time of 12 h. The results are in good agreement with the results from Fukui functions calculations. The kinetic experiments revealed that the Li and Co extraction is controlled by solution and electron diffusion through the DES. Furthermore, a cubic cobalt oxide spinel (Co
3
O
4
) was obtained from the loaded DES using H
2
C
2
O
4
and NaOH in the dilution-precipitation-calcination process. The current strategy demonstrates great potential for rapid and reliable screening of suitable DESs for the effective recycling of spent LIBs.
Deep eutectic solvents (DESs), as a green alternative technology, exhibit great potential to recycle valuable elements from spent lithium-ion batteries (LIBs).
A new type of multistimuli‐responsive hydrogels cross‐linked by metal ions and biopolymers is reported. By mixing the biopolymer chitosan (CS) with a variety of metal ions at the appropriate pH ...values, we obtained a series of transparent and stable hydrogels within a few seconds through supramolecular complexation. In particular, the CS–Ag hydrogel was chosen as the model and the gelation mechanism was revealed by various measurements. It was found that the facile association of Ag+ ions with amino and hydroxy groups in CS chains promoted rapid gel‐network formation. Interestingly, the CS–Ag hydrogel exhibits sharp phase transitions in response to multiple external stimuli, including pH value, chemical redox reactions, cations, anions, and neutral species. Furthermore, this soft matter showed a remarkable moldability to form shape‐persistent, free‐standing objects by a fast in situ gelation procedure.
Turning to jelly: A series of metal–biopolymer hydrogels is obtained by ultrafast supramolecular complexation. The hydrogels are easily prepared, have high water content, and are stable at room temperature. The multistimuli‐responsive Ag‐based hydrogel can be molded to form shape‐persistent, free‐standing objects.
Phosphorus doping is an effective strategy to simultaneously improve the electronic conductivity and regulate the ionic diffusion kinetics of TiO2 being considered as anode materials for sodium ion ...batteries. However, efficient phosphorus doping at high concentration in well-crystallized TiO2 nanoparticles is still a big challenge. Herein, we propose a defect-assisted phosphorus doping strategy to selectively engineer the surface structure of TiO2 nanoparticles. The reduced TiO2–x shell layer that is rich in oxygen defects and Ti3+ species precisely triggered a high concentration of phosphorus doping (∼7.8 at. %), and consequently a TiO2@TiO2–x -P core@shell architecture was produced. Comprehensive characterizations and first-principle calculations proved that the surface-functionalized TiO2–x -P thin layer endowed the TiO2@TiO2–x -P with substantially enhanced electronic conductivity and accelerated Na ion transportation, resulting in great rate capability (167 mA h g–1 at 10 000 mA g–1) and stable cycling (99% after 5000 cycles at 10 A g–1). Combining in/ex situ X-ray diffraction with ex situ electron spin resonance clearly demonstrated the high reversibility and robust mechanical behavior of TiO2@TiO2–x -P upon long-term cycling. This work provides an interesting and effective strategy for precise heteroatoms doping to improve the electrochemical performance of nanoparticles.
Conventional development of nanomaterials for efficient electrocatalysis is largely based on performance‐oriented trial‐and‐error/iterative approaches, while a rational design approach at the ...atomic/molecular level is yet to be found. Here, inspired by a fundamental understanding of the mechanism for both oxygen and hydrogen evolution half reactions (OER/HER), a unique strategy is presented to engineer RuO2 for superior alkaline water electrolysis through coupling with NiO as an efficient bifunctional promoter. Benefitting from desired potential‐induced interfacial synergies, NiO‐derived NiOOH improves the oxygen binding energy of RuO2 for enhanced OER, and NiO also promotes water dissociation for enhanced HER on RuO2‐derived Ru. The resulting hybrid material exhibits remarkable bifunctional activities, affording 2.6 times higher OER activity than that of RuO2 and an HER activity comparable to Pt/C. As a result, the simple system requires only 1.5 V to deliver 10 mA cm−2 for overall alkaline water splitting, outperforming the benchmark PtC/NF||IrO2/NF couple with high mass loading. Comprehensive electrochemical investigation reveals the unique and critical role of NiO on the optimized RuO2/NiO interface for synergistically enhanced activities, which may be extended to broader (electro)catalytic systems.
Porous nanosheet arrays consisting of strongly interacting RuO2 and NiO nanoparticles are grown vertically on nickel foam through a simple hydrothermal reaction, chemical etching, and thermal treatment process. The self‐supported electrode performs as a highly efficient bifunctional electrocatalyst for overall alkaline water splitting. Its enhanced activity is largely due to the potential‐induced interfacial synergy originating from its rational design.
A simple one‐pot solvothermal method is reported to synthesize VS2 nanosheets featuring rich defects and an expanded (001) interlayer spacing as large as 1.00 nm, which is a ≈74% expansion as ...relative to that (0.575 nm) of the pristine counterpart. The interlayer‐expanded VS2 nanosheets show extraordinary kinetic metrics for electrocatalytic hydrogen evolution reaction (HER), exhibiting a low overpotential of 43 mV at a geometric current density of 10 mA cm−2, a small Tafel slope of 36 mV dec−1, and long‐term stability of 60 h without any current fading. The performance is much better than that of the pristine VS2 with a normal interlayer spacing, and even comparable to that of the commercial Pt/C electrocatalyst. The outstanding electrocatalytic activity is attributed to the expanded interlayer distance and the generated rich defects. Increased numbers of exposed active sites and modified electronic structures are achieved, resulting in an optimal free energy of hydrogen adsorption (∆GH) from density functional theory calculations. This work opens up a new door for developing transition‐metal dichalcogenide nanosheets as high active HER electrocatalysts by interlayer and defect engineering.
VS2 nanosheets featuring rich defects and an expanded (001) interlayer spacing as large as 1.00 nm are synthesized by a solvothermal method and demonstrate extraordinary kinetic metrics for the hydrogen evolution reaction. The electrocatalytic activity enhancement is attributed to the optimal free energy of hydrogen adsorption (∆GH) based on the molecular simulation.
It is a challenge to prepare organic electrodes for sodium-ion batteries with long cycle life and high capacity. The highly reactive radical intermediates generated during the sodiation/desodiation ...process could be a critical issue because of undesired side reactions. Here we present durable electrodes with a stabilized α-C radical intermediate. Through the resonance effect as well as steric effects, the excessive reactivity of the unpaired electron is successfully suppressed, thus developing an electrode with stable cycling for over 2,000 cycles with 96.8% capacity retention. In addition, the α-radical demonstrates reversible transformation between three states: C=C; α-C·radical; and α-C
anion. Such transformation provides additional Na
storage equal to more than 0.83 Na
insertion per α-C radical for the electrodes. The strategy of intermediate radical stabilization could be enlightening in the design of organic electrodes with enhanced cycling life and energy storage capability.
Ni3S2 nanowire arrays doped with vanadium(V) are directly grown on nickel foam by a facile one-step hydrothermal method. It is found that the doping can promote the formation of Ni3S2 nanowires at a ...low temperature. The doped nanowires show excellent electrocatalytic performance toward hydrogen evolution reaction (HER), and outperform pure Ni3S2 and other Ni3S2-based compounds. The stability test shows that the performance of V-doped Ni3S2 nanowires is improved and stabilized after thousands of linear sweep voltammetry test. The onset potential of V-doped Ni3S2 nanowire can be as low as 39 mV, which is comparable to platinum. The nanowire has an overpotential of 68 mV at 10 mA cm–2, a relatively low Tafel slope of 112 mV dec–1, good stability and high Faradaic efficiency. First-principles calculations show that the V-doping in Ni3S2 extremely enhances the free carrier density near the Fermi level, resulting in much improved catalytic activities. We expect that the doping can be an effective way to enhance the catalytic performance of metal disulfides in hydrogen evolution reaction and V-doped Ni3S2 nanowire is one of the most promising electrocatalysts for hydrogen production.
Partially graphitic hierarchical porous carbon nanofiber is prepared via electrospinning, pyrolysis, activation and acid treatment of the nascent fiber. The ameliorating structural features of the ...as-obtained carbon nanofiber, such as a relatively high graphitic degree, a high specific surface area and a large pore volume with hierarchical porous structure, acted synergistically, resulting in excellent electrochemical properties. When applied in supercapacitors, the obtained sample delivers a high specific capacitance of 287 F g−1 at 0.5 A g−1, a high rate capacitance of 196 F g−1 at 100 A g−1 and a high capacity retention of 95.4% at 5 A g−1 after 10,000 cycles. When used as an anode for lithium ion batteries, the prepared electrodes display an exceptionally high reversible capacity of 1495 mAh g−1 at 0.1 A g−1, superior cycle stability and an outstanding high-rate capacity of 391 mAh g−1 at 10 A g−1 for 1100 cycles. These values demonstrate the superiority of partially graphitic hierarchical porous carbon nanofiber as bi-functional electrodes in supercapacitors and Li-ion batteries with outstanding performance.
•A partially graphitic hierarchical porous CNF was synthesized.•It owns ultra-high specific surface area of 2721 m2 g−1.•It shows excellent electrochemical performances as bi-functional electrode.
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•Waste pomelo peel converted into a novel adsorbent for use in CDI.•Removal of Pb and Cu ions strongly enhanced by functionalizing with pyrrolic-N.•Strong selectivity of Pb2+ from ...water containing multiple competing ions.•Easy regeneration of adsorbent on no loss in performance over 300 cycles.
Water is not only a valuable resource that is needed to sustain life, but also an essential ingredient in many engineering processes, which unavoidably leads to large volumes of water being contaminated. To achieve safe discharge and also recover valuable “pollutants”, better performing sorbents are needed to rapidly and efficiently decontaminate water while generating minimal secondary wastes. Bio-sorbents derived from pomelo peel were functionalized with pyrrolic-N (BNC-5 electrode) and pyridinic-N (BNC-6 electrode) to enhance electroadsorption and selectivity of Pb2+ and Cu2+. The interaction between soft acid ions (Pb2+) and soft base sites (pyrrolic-N) contributed to a strong chemisorption that elevated the electroadsorption capacity to 2.0 mmol g−1 for Pb2+ at an applied voltage of 1.2 V. With fast removal kinetics (0.077 g mg−1 min−1 of Pb2+), the BNC-5 sorbent performed comparably to other N-doped sorbents prepared using graphene. The large adsorption–desorption hysteresis of BNC-5 in responding to the applied electric voltage confirmed the nature of chemisorption. The results showed only 32.4% of the adsorbed ions being desorbed from the sorbent by reducing the applied voltage to 0 V, but reached almost complete desorption (98.5% of adsorbed ions) at –0.8 V. When operated in adsorption–desorption cycle mode, BNC-5 after ∼ 400 cycles maintained a capacity retention ≥ 80%. After 400 cycles, the electrode capacity was almost fully restored (98.7%) by only mild chemical washing (0.1 M HNO3) of the sorbent and the cycling performance maintained. The study demonstrated the robustness of the sorbent over 1200 cycles and hence the potential to successfully convert waste into high-performance materials for large-scale remediation strategies of contaminated wastewater using CDI.
Discovering highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is critical to the commercial development of many next-generation energy conversion and storage devices, ...with Fe-doped nickel (oxy)hydroxide representing one of the most promising OER catalysts developed to date. However, the active sites and mechanism of OER on Fe-doped nickel (oxy)hydroxide catalysts remain unclear. To gain deeper insights into the role of metal dopants in enhancing OER activity, we explored here the role of Ir-doping in the OER performance of nickel (oxy)hydroxide catalysts, placing particular emphasis on the nature of the active site. Density functional theory calculations with Hubbard U correction revealed that Ir-doping of a β-NiOOH(001) surface enhanced the electric conductivity while also activating an oxygen site involving three Ni atoms (Ni3 site) to realize a remarkably low OER overpotential of only η = 0.46 V, much lower than the overpotential on the oxygen site involving Ir + two Ni atoms (IrNi2 site, η = 0.77 V) or the oxygen site involving three Ni atoms in pristine β-NiOOH (η = 0.66 V). Guided by the computational results, ultrathin Ir-doped Ni(OH)2 nanosheets were then fabricated through a combination of hydrothermal assembly and liquid exfoliation, with the nanosheets transforming to Ir-doped NiOOH during OER and offering superior activity relative to pristine Ni(OH)2 nanosheets or a commercial IrO2 catalyst, thereby validating the theoretical predictions. The computational and experimental results thus conclusively demonstrate that Ir-doping and nanosheet engineering are synergistic strategies for tuning the electronic and structural properties of nickel (oxy)hydroxides for improved oxygen evolution electrocatalysis.
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