Luyi Chen,Ping Xiao,Bin Hu,Yiwen Wang,Jianmao Yang,Jianyun Liu
3-dimensional (3D) Fe−Co−LDH/MXene composite was synthesized by in-situ synthesis and assembly of Fe−Co−LDH rod around MXene under hydrothermal condition. Due to the unique 3D configuration and good conductivity, the obtained Fe−Co−LDH/MXene modified glassy carbon electrode (Fe−Co−LDH/MXene/GCE) showed excellent electrochemical activity for As(III) detection. Via square-wave anodic stripping voltammetry, the response current on Fe−Co−LDH/MXene/GCE had good linear relationship with As(III) concentrations (1∼1000 ppt) with superior sensitivity (0.22 μA ppt −1 cm −2 ) and low detection limit (0.9 ppt). The mechanism of As(III) adsorption was demonstrated. The electrode showed excellent anti-interference ability. Real water sample analysis demonstrated the Fe−Co−LDH/MXene/GCE was deployable in aqua-system.
Capacitive deionization (CDI) is considered one of the most promising desalination technologies for obtaining fresh water from saline water. In this work, we synthesized a hollow core–shell Co-MOF@Fe/Co-LDH (Co-Fe-LDH) material by developing a strategy to simultaneously grow Co/Fe-LDH on the surface of a Co-MOF precursor in situ. Owing to the increase in the specific surface area of the hollow structure and the Faradaic process of a layered double hydroxide (LDH), the Co-Fe-LDH material exhibits high electrical double layer (EDL) capacitance and pseudocapacitance, which significantly improves the salt adsorption of the material during CDI (34.2 mg/g in a 600 mg/L NaCl solution at 1.2 V). The adsorption for NaCl in this work is approximately 2.5 times the maximum salt adsorption capacity (SAC) of LDH materials applied in nonmembrane CDI (NMCDI). This work may provide a promising model for the application of hollow LDH materials that exhibit pseudocapacitance in CDI.
Liying Wu,Zhiqiang Sun,Yufei Zhen,Shishu Zhu,Chen Yang,Jing Lu,Yu Tian,Dan Zhong,Jun Ma
Ubiquitous oxygen vacancies (Vo) existing in metallic compounds can activate peroxymonosulfate (PMS) for water treatment. However, under environmental conditions, especially oxygenated surroundings, the interactions between Vo and PMS as well as the organics degradation mechanism are still ambiguous. In this study, we provide a novel insight into the PMS activation mechanism over Vo-containing Fe–Co layered double hydroxide (LDH). Experimental results show that Vo/PMS is capable of selective degradation of organics via a single-electron-transfer nonradical pathway. Moreover, O2 is firstly demonstrated as the most critical trigger in this system. Mechanistic studies reveal that, with abundant electrons confined in the vacant electron orbitals of Vo, O2 is thermodynamically enabled to capture electrons from Vo to form O2•– under the imprinting effect and start the activation process. Simultaneously, Vo becomes electron-deficient and withdraws the electrons from organics to sustain the electrostatic balance and achieve organics degradation (32% for Bisphenol A without PMS). Different from conventional PMS activation, under the collaboration of kinetics and thermodynamics, PMS is endowed with the ability to donate electrons to Vo as a reductant other than an oxidant to form 1O2. In this case, 1O2 and O2•– act as the indispensable intermediate species to accelerate the circulation of O2 (as high as 14.3 mg/L) in the micro area around Vo, and promote this nano-confinement electron-recycling process with 67% improvement of Bisphenol A degradation. This study provides a brand-new perspective for the nonradical mechanism of PMS activation over Vo-containing metallic compounds in natural environments.
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