Hexagonal close-packed Ni (h-Ni) nanocrystals and face-centered cubic Ni (c-Ni) nanoflowers with uniform size and high dispersion have been successfully assembled on graphene nanosheets (GN) via a facile one-step solution-phase strategy under different reaction conditions, where the reduction process of graphite oxide (GO) sheets into GN was accompanied by the generation of Ni nanocrystals. The reduction of GO by this method is effective, which was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy and is comparable to conventional methods. The phase and morphology of nickel can be easily tuned by varying the reaction temperature and solvent. It was shown that the as-formed h-Ni nanocrystals with a diameter as small as 3 nm are grown densely and uniformly on the graphene sheets, and as a result the aggregation of the h-Ni nanocrystals was effectively prevented. In addition, c-Ni nanospheres assembled by c-Ni nanocrystals with a size of 15 nm were also uniformly deposited on the graphene sheets. The investigation of the microwave absorbability reveals that the three Ni/GN nanocomposites exhibit excellent microwave absorbability, which is stronger than the corresponding Ni nanostructures.

It is a challenge to regulate charge flow synergistically at the atomic level to modulate gradient hydrogen migration (H migration) for boosting photocatalytic hydrogen evolution. Herein, a self-adapting S vacancy (Vs) induced with atomic Cu introduction into ZnIn 2 S 4 nanosheets was fabricated elaborately, which can tune charge separation and construct a gradient channel for H migration. Detailed experimental results and theoretical simulations uncover the behavior mechanism of Vs generation with Cu introduction after substituting a Zn atom tendentiously. Cu−S bond shrinkage and Zn−S bond distortion are presented around Vs areas. Besides, Vs induced by Cu introduction lowers the internal electric field to restrain electron transmission between layers, which are enriched on the Vs area because of the lower surface electrostatic potential. Atomic Cu and Vs show a synergistic effect for regulating regional charge separation due to the Cu dopant being a hole trap and Vs being an electron trap. The channels for H migration with gradient ΔG H 0 are constructed by different S atom sites, which are modulated by Vs. Gradient H migration driven by a photothermal effect occurs on an identical surface without striding across a heterogeneous interface, which is a valid pathway with lower resistance for boosting H 2 release. Ultimately, 5 mol % Cu confined in ZnIn 2 S 4 nanosheets achieves an optimum photocatalytic hydrogen evolution activity of 9.8647 mmol g −1 h −1 , which is 14.8 times higher than 0.6640 mmol g −1 h −1 for ZnIn 2 S 4 , and apparent quantum efficiency reaches 37.11% at 420 nm. This work demonstrates the behavior mechanism of atomic substitution and provides cognition for hydrogen evolution mechanism deeply.

Recycling lithium from waste lithium batteries is a growing problem, and new technologies are needed to recover the lithium. Currently, there is a lack of highly selective adsorption/ion exchange materials that can be used to recover lithium. We have developed a magnetic lithium ion-imprinted polymer (Fe 3 O 4 @SiO 2 @IIP) by using novel crown ether. The Fe 3 O 4 @SiO 2 @IIP has been synthesized by a surface imprinting technique using our newly synthesized 2-(allyloxy) methyl-12-crown-4 as a functional monomer. The Fe 3 O 4 @SiO 2 @IIP was analyzed by Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The optimum pH for adsorption is 6. Fe 3 O 4 @SiO 2 @IIP shows fast adsorption kinetics for lithium ions (10 min to reach complete equilibrium), and the adsorption process obeys an external mass transfer model. Homogeneous binding sites are proved by the Langmuir isotherm, and the maximum adsorption capacity is 0.586 mmol/g. Fe 3 O 4 @SiO 2 @IIP has excellent selectivity for Li(I) because the selectivity separation factors of Li(I) with respect to Na(I), K(I), Cu(II), and Zn(II) are 50.88, 42.38, 22.5, and 22.2, respectively. The adsorption capacity of sorbent remained above 92% after five cycles. Fixed-bed column adsorption experiments indicate that the effective treatment volume was 140 bed volumes (BV) in the first run with a breakthrough of 10% of the inlet concentration for an inlet concentration of 0.5 mmol/L, and 110 BV was treated for the second run under identical conditions. We demonstrated that 89.8% of the lithium was recovered during bed regeneration using 0.5 mol/L HCl solution. Fe 3 O 4 @SiO 2 @IIP also exhibited excellent removal efficiency for Li(I) in real wastewater, validating its great potential in advanced wastewater treatment. Accordingly, we have developed a new method for wastewater treatment that meets Li emission standards, and recovery of Li creates economic interest.

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