Lianyi Shao,Songying Wang,Kaiqiang Wu,Miao Shui,Rui Ma,Dongjie Wang,Nengbing Long,Yuanlong Ren,Jie Shu
Comparison of (BiO) 2 CO 3 to CdCO 3 as anode materials is investigated in this paper. Electrochemical results show that both (BiO) 2 CO 3 and CdCO 3 are electrochemically active materials with high initial capacities of 1080.1 and 1251.1 mAh g −1 , respectively. Ex-situ X-ray diffraction (XRD) results show that the electrochemical reaction mechanisms of CdCO 3 with Li can be associated with the preliminary formation of Cd and Li 2 CO 3 upon the initial lithiation, and then the final formation of LiCd alloy upon further lithiation. In contrast, the electrochemical reaction of (BiO) 2 CO 3 with Li not only results in the formation of Bi and Li 2 CO 3 , but also induces the formation of Li 2 O. Besides, upon further lithiation, the alloying reaction of Bi with Li is a multi-step process to form LiBi, Li x Bi, and finally Li 3 Bi as confirmed by electrochemical behaviors and in-situ XRD technique. Compared with CdCO 3 , (BiO) 2 CO 3 can exhibit better electrochemical properties with a reversible capacity of 155.1 mAh g −1 and a capacity retention of 28.3% after 15 cycles. By introducing carbon black as conductive additive and volume change buffer, the reversible capacity of ball-milled (BiO) 2 CO 3 /C composite can be improved to the value of 297.6 mAh g −1 with a capacity retention of 47.8% after 15 cycles.
Wen-Yi Wang,Tian Sang,Yan Zhong,Chao-Hao Hu,Dian-Hui Wang,Jun-Chen Ye,Ni-Ni Wei,Hao Liu
The surfactant modification of catalyst morphology is considered as an effective method to improve photocatalytic performance. In this work, the visible-light-driven composite photocatalyst was obtained by growing CdS nanoparticles in the cubic crystal structure of CdCO3, which, after surfactant modification, led to the formation of CdCO3elliptical spheres. This reasonable composite-structure-modification design effectively increased the specific surface area, fully exposing the catalytic-activity check point. Cd2+from CdCO3can enter the CdS crystal structure to generate lattice distortion and form hole traps, which productively promoted the separation and transfer of CdS photogenerated electron-hole pairs. The prepared 5-CdS/CdCO3@SDS exhibited excellent Cr(VI) photocatalytic activity with a reduction efficiency of 86.9% within 30 min, and the reduction rate was 0.0675 min−1, which was 15.57 and 14.46 times that of CdS and CdCO3, respectively. Finally, the main active substances during the reduction process, the photogenerated charge transfer pathways related to heterojunctions and the catalytic mechanism were proposed and analyzed.Keywords:surfactant;CdS/CdCO3;photocatalytic;Cr(VI)
Qian Sun,Cun Liu,Peixin Cui,Tingting Fan,Mengqiang Zhu,Marcelo Eduardo Alves,Matthew G. Siebecker,Donald L. Sparks,Tongliang Wu,Wei Li,Dongmei Zhou,Yujun Wang
Apart from surface complexation, precipitation of minerals also plays an important role in reducing the mobility and transport of heavy metals in the environment. In this study, Cd(II) sorption species on surfaces of γ-Al 2 O 3 at pH 7.5 were characterized using multiple techniques. Results show that in addition to adsorption complexes, Cd hydroxide phases (Cd(OH) 2 precipitates and Cd x (OH) y polynuclear complexes) were formed at the initial stages of Cd(II) sorption and gradually transformed to CdCO 3 with time. In addition, Cd(II) formed Cd Al layered double hydroxide (LDH) on γ-Al 2 O 3 under various conditions, independent of temperature and Cd loadings. The formation of Cd hydroxide phases and Cd Al LDH could be ascribed to surface-induced precipitation because the bulk solution was undersaturated with respect to hydroxides. Cd Al LDH formation on the Al-bearing mineral here is rather surprising because typically this occurs with elements of ionic radii similar to that of Al 3+ ; this formation is unknown for metals such as Cd(II) with a much larger ionic radius. The thermodynamic feasibility of Cd Al LDH formation was further confirmed by laboratory synthesis of Cd Al LDH and density function theory (DFT) calculations. These results suggest that Cd precipitation on Al-bearing minerals can be an important mechanism for Cd immobilization in the natural environment. Additionally, the finding of Cd Al LDH formation on Al-bearing minerals and the thermodynamic stability of Cd Al LDH provides new insights into the remediation of Cd-polluted soils and aquatic systems.
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