MXene quantum dots (QDs) are emerging 0D nanomaterials. Here, a new heterostructure is developed based on a 1D photoactive semiconductor and a 0D MXene QD for improved photocatalytic reduction of CO2 ...into methanol. Specifically, Ti3C2 QDs are incorporated onto Cu2O nanowires (NWs) through a simple self‐assembly strategy. It is demonstrated that Ti3C2 QDs not only significantly improve the stability of Cu2O NWs but also greatly improve their photocatatlytic performance by enhancing charge transfer, charge transport, carrier density, light adsorption, as well as by decreasing band bending edge and charge recombination. The energy level diagram derived from both experimental measurements and theoretical calculations provide further insights of such hierarchical photocatalysis system.
Ti3C2 quantum dots greatly enhance the photocatalytic ability of Cu2O nanowires for CO2 conversion by promoting charge transfer, decreasing band bending edge, and increasing carrier density.
Graphene quantum dots (GQDs), which is the latest addition to the nanocarbon material family, promise a wide spectrum of applications. Herein, we demonstrate two different functionalization ...strategies to systematically tailor the bandgap structures of GQDs whereby making them snugly suitable for particular applications. Furthermore, the functionalized GQDs with a narrow bandgap and intramolecular Z-scheme structure are employed as the efficient photocatalysts for water splitting and carbon dioxide reduction under visible light. The underlying mechanisms of our observations are studied and discussed.
Graphene quantum dot (GQD) is the most recent addition to the nanocarbon materials family which promises a wide spectrum of novel applications. On the other hand, bimetallic phosphides are emerging ...for their unique potentials for electrocatalysis. Herein, we have demonstrated the fabrication of heterostructured nanosheet arrays of ternary nickel-cobalt phosphide (NiCo2P2) and GQD hybrid (NCP/G NSs) and the use as bifunctional catalysts for overall water splitting in alkaline medium. NCP/G NSs exhibit excellent electrocatalytic activity towards hydrogen evolution reaction (reaching 100 mA cm−2 at an extremely low overpotential of 119 mV), superior to any other non-noble metal catalyst. Furthermore, an electrolyzer equipped with two identical NCP/G NS electrodes at an exceptionally small amount of catalyst loading (0.31 mg cm−2) is able to achieve efficient overall water splitting (10 mA cm−2 at 1.61 V) with high stability. The careful comparison with NiCo2P2 nanowires (NCP NWs) synthesized under the same conditions without GQDs (in terms of electrocatalytic performance, atomic and electronic structures, and electrochemical properties) reveals the mechanistic roles of GQDs in morphology control and performance enhancement. In addition, the performance comparison with ternary nickel-cobalt oxide (NiCo2O4) and GQD hybrid (NCO/G NSs) suggests the advantage of bimetallic phosphides over oxide counterparts.
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•Heterostructured nanosheet arrays of ternary nickel-cobalt phosphide and GQD is efficient for alkaline water splitting.•The HER activity of NCP/G NSs (with an extremely low overpotential of 119 mV to achieve 100 mA cm-2) is currently matchless.•The performance of catalyst is attributed to the critical role of GQD in morphology control and improving catalytic kinetics.
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•Current status on pretreatment of spent Li-ion batteries is presented.•The spent Li-ion battery handling processes are reviewed.•The laboratory and industrial Li-ion battery ...pretreatment applications are reviewed.•This review provides a rundown of limitations that will help to do further research.
The production of lithium-ion batteries (LIBs) is increasing rapidly because of their outstanding physicochemical properties, which ultimately leads to an increasing amount of spent lithium-ion batteries reaching their end-of-life (EOL). Pretreatment of the discarded batteries is an indispensable part of recycling spent lithium-ion batteries. The batteries contain toxic chemicals and high-value metals that must be recycled to promote environmental protection and sustainability. This paper provides an overview of the current pretreatment methods employed in the recycling of spent LIBs. In particular, the article reviews various options (mechanical, chemical, and thermal pretreatment options) that can be adopted for the pretreatment of spent lithium-ion batteries and puts forward the recommendations for future research and development that will enable more efficient and cleaner technologies for recycling spent LIBs. The review emphasizes the safe pretreatment of the spent LIBs and provides an overview of the consequences of the individual pretreatment steps on the recyclability of the materials to be recovered, and LiCoO2 was chosen as the reference as most studies in the literature focus on LiCoO2 cathode materials. However, discussions on other battery chemistries have also been incorporated into the scope of the review.
This paper presents a dry grinding and carbonated ultrasound-assisted water leaching (CUAWL) process for recycling the black mass of spent lithium-ion batteries constituting anode material (graphite) ...and different cathode material combinations (LiCoO2, LiMn2O4, and LiNiO2). The inspiration of the method is to enhance selective Li2CO3 recovery and reduce energy requirements for evaporative crystallization while achieving maximum recovery of all the high-value metals. The influence of several factors, including roasting temperature, roasting time, grinding time, water leaching time, water leaching temperature, sonication, and CO2 flow rate, on the leaching efficiency of metals are investigated. The SEM-EDS and XRD results depict that the mixture of anode and cathode material after reduction roasting under optimum conditions of 600 °C for 30 min was primarily transformed into Li2CO3, Ni, CoO, Co, and MnO. However, the selective recovery of Li with water leaching was low, and dry grinding followed by CUAWL was adopted to enhance the recovery rate. The optimized experimental results achieved improved results for selective recovery of Li of up to 92.25% for the mixture of multiple cathode materials (LiCoO2, LiMn2O4, and LiNiO2). The recovered leach solution (LiHCO3) is subjected to evaporative crystallization to attain high-purity Li2CO3 (≥99.2%). Subsequently, over 99% of the high-value metals Ni, Mn, and Co could be leached out using 4 M H2SO4 without the addition of a reductant.
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•A complete process of gold recovery from sulfide refractory gold ore was proposed.•The recovery efficiency of Au was increased by adding pyrite during the chlorination roasting.•The ...maximum recovery efficiency of gold reached 98.06% under optimal condition.
Recovering gold from sulfide refractory gold ore has been an important guarantee for the sustainable development of gold industry, while there are many challenges in the treatment of sulfide refractory gold ore, such as environmental pollution and low gold recovery. In this study, A novel method for gold recovery from refractory gold ore was proposed with the purpose of improving recovery efficiency of gold and reducing environmental pollution. The method consisted of two stages roasting for arsenic and sulfur removal, gold recovery by thiourea leaching, followed by an enhanced chlorination roasting for gold recovery in the presence of pyrite. In the two-stage roasting process, the phase transition of FeAsS and FeS2 during the roasting process was analyzed. In the first stage roasting process, the removal efficiency of arsenic reached 96.98% with only 43.07% sulfur was removed. We achieved removal efficiency of 97.19% for sulfur and 84.11% of gold was exposed during the second stage roasting process. The thiourea leaching combined with pyrite enhanced chlorination roasting was first proposed to effectively extract gold from the second stage roasting slag, and the pyrite shown a great role in promoting gold extraction during chlorination roasting. In this process, gold could be effectively recovered from the sulfide refractory gold ore with a recovery efficiency of 98.06%.
Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg(2+) type orange peel adsorbent) and KOP (K(+) type orange peel adsorbent). FTIR and SEM were used to characterize ...the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu(2+) adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu(2+) by both MgOP and KOP, and the mono-layer adsorption capacity for Cu(2+) removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu(2+) increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu(2+) by MgOP and KOP.
In this paper, a novel turbo-coded 16-ary orbital angular momentum - shift keying-free space optical (OAM-SK-FSO) communication system combining a convolutional neural network (CNN) based adaptive ...demodulator under strong atmospheric turbulence is proposed for the first time. The feasibility of the scheme is verified by transmitting a 256-grayscale two-dimensional digital image. The bit error ratio (BER) performance of the system is investigated and the effect of different factors such as turbulence strength, propagation distance, code rate, length of random interleaver and length of bit interleaver is also taken into account. An advanced encoder/decoder structure and mapping scheme are applied to diminish the influence of CNN misclassification and reduce the BER effectively. With the optimal encoder/decoder structure and CNN model settings, the BER varies from 0 to 4.89×10
when the propagation distance increases from 200m to 1000m for a given turbulence strength Cn2 equals 5×10
m
. For a determined propagation distance equals 400m, the BER ranges from 0 to 4.01×10
when Cn2increases from 1×10
m
to 4×10
m
. Our numerical simulations demonstrate that the proposed system can provide better BER performance under strong atmospheric turbulence and conditions when the classification ability of CNN is limited.
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•Liquid metal dealloying results in both chemical and structural changes of the alloy.•The applications of liquid metal dealloying for recycling alloy scraps are discussed.•A variety ...of nanoporous materials can be fabricated by liquid metal dealloying.•The morphology parameters of porous metal can be adjusted by dealloying conditions.
Liquid metal dealloying, a method of etching based on different solubilities of each component of the alloy into the liquid metal, has been extensively developed for metallurgical and structural materials applications. This review discusses the development on liquid metal dealloying for recycling alloy scraps and the fabrication of nano-porous materials. Extracting and recycling the valuable metal from alloy scraps by liquid metal dealloying can be more efficient and environmentally friendlier comparing to traditional alloy treatment processes for metal recovery. Manufacturing of nano-porous materials by liquid metal dealloying, not only can meet the need for efficient production of less noble metal nano-porous materials, but also can precisely control the morphology of the nano-pores by adjusting the dealloying conditions. This review demonstrates that liquid metal dealloying opens new avenues for the recycling of alloy scraps and for the fabrication of nano-porous metals, in addition to a wide variety of other promising applications.
As the concept of promoting environmental protection and energy conservation becomes more and more popular, reasonably green approaches for preparing high-performance nanostructured Fe2O3 anodes will ...be well received. Herein, porous Fe2O3 quasi-clusters assembled by smaller secondary nanoparticles have been successfully prepared by direct calcination of commercial ferric citrate in air atmosphere. Comparing with the traditionally hydrothermal methods of preparing various nanostructured Fe2O3, our approach are more facile and green because of no use of various solvents and reagents, and additional time- and power-consuming hydrothermal treatment. More importantly, the as-prepared Fe2O3 quasi-clusters show excellent electrochemical performance, delivering high capacities of 1187.1 and 448.3 mAh g−1 at 200 and 3000 mA g−1 after 350 and even 1500 cycles, respectively. Even comparing with the reported state-of-the-art nanostructural Fe2O3 anodes, the performance of as-prepared Fe2O3 quasi-clusters is competitive and even better. Thus, due to the relatively green and extremely facile preparation process, and excellent electrochemical performance, the as-achieved Fe2O3 quasi-clusters are expected as a promising candidate for advanced anode materials of lithium-ion batteries.
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•A high-performance Fe2O3 anode had been prepared by an extremely facile way.•This preparation approach was more facile and green than that of traditional ways.•This Fe2O3 anode exhibited excellent lithium storage performance.•It delivered a high capacity of 1187.1 mAh g−1 after even 350 cycles.
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