Single-atom catalysts (SACs) show great promise for electrochemical CO 2 reduction reaction (CRR), but the low density of active sites and the poor electrical conduction and mass transport of the single-atom electrode greatly limit their performance.H erein, we prepared an ickel single-atom electrode consisting of isolated, high-density and low-valent nickel(I) sites anchored on as elf-standing N-doped carbon nanotube array with nickel-copper alloy encapsulation on acarbon-fiber paper.The combination of single-atom nickel(I) sites and self-standing arraystructure gives rise to an excellent electrocatalytic CO 2 reduction performance.T he introduction of copper tunes the d-band electron configuration and enhances the adsorption of hydrogen, which impedes the hydrogen evolution reaction. The single-nickel-atom electrode exhibits as pecific current density of À32.87 mA cm À2 and turnover frequency of 1962 h À1 at am ild overpotential of 620 mV for CO formation with 97 %F aradic efficiency.
Silicon nanowires have been synthesized by laser ablation of Si powder targets at 1200 °C. Transmission electron microscopy study showed that most Si nanowires had smooth surfaces and nearly the same diameter of about 16 nm. Beside the most abundant smooth-surface nanowires, four other forms of nanowires, named spring-shaped, fishbone-shaped, frog-egg-shaped, and necklace-shaped nanowires, were observed. The formation of nanowires into different shapes was explained by the two-step growth model based on the vapor–liquid–solid mechanism.
Rapid adoption of lithium‐ion batteries for electronics and electric vehicles requires cost‐effective and efficient recycling of battery components especially the valuable cathode active materials. The direct recycling method transforms end‐of‐life (EOL) cathode materials into battery grade materials with minimal energy consumption and least environmental disruption. In direct recycling, the relithiation step to restore the lithium stoichiometry of the cathode materials is critical. In this work, a novel electrochemical relithiation approach in an aqueous electrolyte followed by a heat treatment for recycling cathode materials in EOL lithium‐ion batteries is demonstrated and analyzed. Using LiCoO2 as an example, it is shown that the recycled LiCoO2 materials show equivalent crystal structure, morphology, and electrochemical performance to the commercial LiCoO2.
The development of inexpensive and highly efficient nonprecious metal catalysts to substitute Pt in the alkaline oxygen reduction reaction is an appealing idea in the energy field. Herein, a Mn oxygen reduction electrocatalyst with a half‐wave potential (E1/2) as high as 0.910 V under an alkaline oxygen reduction reaction process is developed, and the dynamic atomic structure change of the highly efficient Mn single‐atomic site is investigated using operando X‐ray absorption spectroscopy. These results demonstrate that the low‐valence MnL+N4 is the active site during the oxygen reduction process. Density functional theory reveals that facile electron transfer from MnL+N4 to adsorbed *OH species plays a key role in the excellent electrocatalytic performance. Moreover, when assembled as the cathode in a zinc–air battery, this MnN4 material shows high power density and excellent durability, demonstrating its promising potential to substitute the Pt catalyst in practical devices.
Metal−organic frameworks (MOFs) with uniform porous structures show great promise for size/shape-selective catalysis, but their microsized pores and narrow channels inherently limit the diffusion of catalytic substrates and their catalytic efficiency. Herein, we report the fabrication of a hollow mesoporous MOF with hollow macroporous core and mesoporous shell, featuring a hierarchical porous structure that allows fast diffusion of reactants. The hollow core and mesoporous shell of the MOF were achieved by an elaborate design of a bimetallic MOF with stability differences in both metal−ligand bonds and spatial distribution via a boosted nucleation process, followed by selective etching treatment. Impressively, the hollow mesoporous MOF greatly enhanced the mass diffusion within the framework, which is demonstrated by the diffusion experiments, the molecular dynamics simulation, and the catalytic reaction by using 4chlorostyrene as a probe. In addition, the as-prepared hollow mesoporous MOF exhibited superior catalytic performance when utilized as a Pd nanoparticles carrier, compared with solid Pd/MOF and commercial Pd/C catalysts toward benzyl alcohol oxidation.
Highest nuclearity M48 (M = CoII or NiII) cage clusters have been constructed by [12+18] condensation of twelve M4-p-tert-butylthiacalix[4]arene second building units (as vertices) and eighteen asymmetric 5-(1H-tetrazol-1-yl)isophthalate ligands (as faces), showing a merohedral icosahedron-type framework.
Developing active single-atom-catalyst (SAC) for alkaline hydrogen evolution reaction (HER) is a promising solution to lower the green hydrogen cost. However, the correlations are not clear between the chemical environments around the active-sites and their desired catalytic activity. Here we study a group of SACs prepared by anchoring platinum atoms on NiFe-layered-double-hydroxide. While maintaining the homogeneity of the Pt-SACs, various axial ligands (−F, −Cl, −Br, −I, −OH) are employed via a facile irradiation-impregnation procedure, enabling us to discover definite chemical-environments/performance correlations. Owing to its high first-electron-affinity, chloride chelated Pt-SAC exhibits optimized bindings with hydrogen and hydroxide, which favor the sluggish water dissociation and further promote the alkaline HER. Specifically, it shows high mass-activity of 30.6 A mgPt−1 and turnover frequency of 30.3 H2 s−1 at 100 mV overpotential, which are significantly higher than those of the state-of-the-art Pt-SACs and commercial Pt/C catalyst. Moreover, high energy efficiency of 80% is obtained for the alkaline water electrolyser assembled using the above catalyst under practical-relevant conditions.
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