Search

The phase structure and electrochemical properties of La4MgNi17M2(M=Ni,Co,Mn) alloys were investigated in detail. The XRD analysis revealed that the main phases in the alloys are LaNi5 and La4MgNi19 phases (Ce5Co19+Pr5Co19 structure). When the Ni element in the alloy was substituted by Mn or Co, the abundant of La4MgNi19 phase increased, and especially in the La4MgNi17Mn2 alloy, that increased to 70.7%. The electrochemical measurement showed that the activation of La4MgNi17M2(M=Ni,Co,Mn) alloy electrodes were improved, and it only needed 1-2 cycles.what’s more, with the elements substitution for Ni ,the maximum discharge capacity gradually increased to 386.10 mA·h/g (Co) and 375.18 mA·h/g (Mn), but high-rate dischargeability (HRD) decreased somewhat (Co, HRD900=86.2%). It is found that the HRD was mainly controlled by the electrocatalytic activity on the alloy electrode surface, and the decline of cyclic stability was due to the appearance of A5B19 type phase with larger hydrogen storage capacity, which lead to bigger volume expansion or intercrystalline stress, then easier pulverization during charging/discharging. In addition, the cyclic stability (S100) was improved with Co substitution, and worsened with Mn substitution, because Mn element was easily corroded and Co improved the ability of Corrosion resistance.

The influence of substitution Co for Ni on the phase structure and electrochemical properties of La4MgNi19 phase composition alloys have been investigated systematically.The structure analyses show that the alloys are mainly composed of multiphase,such as CaCu5 phase ,Pr5Co19 phase and Ce5Co19 phase.The electrochemical measurement showed that alloy electrodes could be activated in 2-3 cycles, with increasing of x value, the maximum discharge capacity gradually increased from 345.7 mA·h/g (x = 0.0) to 382.8 mA·h/g (x = 2.0), cyclic stability increased a little ,but high-rate dischargeability (HRD) decreased somewhat. It is found that the HRD was mainly controlled by the electrocatalytic activity on the alloy electrode surface,and the improvement of cyclic stability was due to the increase of CaCu5 phase and Ce5Co19 phase . CaCu5 phase increased with increasing Co content. Ce5Co19 phase has a small corrosion rate in the electrochemical cycle.

Mine drainage is a widespread environmental problem associated with both working and abandoned mining operations, resulting from the microbial oxidation of pyrite in presence of water and air, affording a solution that contains toxic metal ions. The present study aimed at evaluating the use of low-cost modified mordenitem to remove heavy metals ions from mine drainage. We elucidate the important parameters (including the pH, temperature, contact time, particle size and dosage) responsible for the removal the heavy metal ions. In addition, selectivity of modified mordenitem for metal removal was, in decreasing order, Pb2+> Cd2+ > Cu2+ > Zn2+. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of mine drainage.

Macroporous ZnO nanofilms were synthesized by a simple hydrothermal reaction. The products exhibit noticable hydrogen storage capacity and big BET surface area. The present work shows that the nanostructures of products are important to their electrochemical hydrogen storage performances. On the other hand, the low cost, convenient process, good reproducibility, high yield, and clean reactions of the present synthetic method make it possible to scale it up to industrial production.