Haiyun Tong,Shuai Lin,Hanlu Zhang,Xin Wang,Yanan Huang,Bangchuan Zhao,Xuebin Zhu,Yuping Sun
The present work reports oxygen evolution reaction (OER) activity in metallic V 4 AlC 3 bulk powders prepared by solid-state reactions for the first time. An ultralow overpotential of 253 mV at the current density of 10 mA cm −2 and an excellent stability are observed, demonstrating that V 4 AlC 3 bulk powder can be used as an excellent new type of OER catalyst with low-cost for mass production.
The V 4 AlC 3 MAX phase, as the precursor of MXene, was developed for levofloxacin degradation through sonocatalytic activation of peroxymonosulfate (PMS). The reactive sintering method was used to synthesize V 4 AlC 3 MAX phase. Vanadium, aluminium and graphite, with molar ratios 4:1.2:3, were mixed in ball milled (ball-to-material ratio of 3:1, 12 h, 350 rpm), compressed into a disc and placed in a tubular furnace (1600 ℃ for 2 h). The stacked layered morphology of the MAX phase was confirmed by SEM and TEM images. With an average crystal size of 48.5 nm and a narrow band gap (1.92 eV), the V 4 AlC 3 MAX phase exhibited remarkable sonocatalytic activity. Under optimum conditions, US/V 4 ALC 3 MAX phase/PMS process exhibited 88.4 % levofloxacin degradation efficiency in 60 min. First order rate constant (k app ) of the US/V 4 AlC 3 MAX phase/PMS process was 10.22, 7.43, and 4.78 times higher than that of US/V 4 AlC 3 MAX phase, US/PMS, and V 4 AlC 3 MAX phase/PMS processes, respectively. V 4 AlC 3 MAX phase showed remarkable reusability after 5 cycles. It was proved that superoxide radical was the main active substance in the degradation process. The possible intermediates were identified through LC-MS analysis, and four main degradation pathways were proposed. The mechanism of PMS-assisted sonocatalytic degradation of levofloxacin was described.
Hydrogen is considered one of the most ideal future energy carriers. The safe storage and convenient transportation of hydrogen are key factors for the utilization of hydrogen energy. In the current investigation, two-dimensional vanadium carbide (VC) was prepared by an etching method using V 4 AlC 3 as a precursor and then employed to enhance the hydrogen storage properties of MgH 2 . The studied results indicate that VC-doped MgH 2 can absorb hydrogen at room temperature and release hydrogen at 170 °C. Moreover, it absorbs 5.0 wt.% of H 2 within 9.8 min at 100 °C and desorbs 5.0 wt.% of H 2 within 3.2 min at 300 °C. The dehydrogenation apparent activation energy of VC-doped MgH 2 is 89.3 ± 2.8 kJ/mol, which is far lower than that of additive-free MgH 2 (138.5 ± 2.4 kJ/mol), respectively. Ab-initio simulations showed that VC can stretch Mg-H bonds and make the Mg-H bonds easier to break, which is responsible for the decrease of dehydrogenation temperature and conducive to accelerating the diffusion rate of hydrogen atoms, thus, the hydrogen storage properties of MgH 2 are remarkable improved through addition of VC.
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