Yujing Wang

Three-Dimensional Homogeneous Ferrite-Carbon Aerogel: One Pot Fabrication and Enhanced Electro-Fenton Reactivity

This work focuses on constructing a high catalytic activity cathode of an electro-Fenton system, to overcome the defects of low activity, poor stability, and intricate fabrication of supported catalysts. A series of ferrite-carbon aerogel (FCA) monoliths with different iron/carbon ratios was synthesized directly from metal-resin precursors accompanied by phase transformation. Self-doped ferrite nanocrystals and carbon matrix were formed synchronously via moderate condensation and sol-gel processes, leading to homogeneous texture. An optimal 5% ferric content FCA was composed of coin-like carbon nano-plate with continuous porous structure, and the ferric particles with diameters of dozens of nanometers were uniformly embedded into the carbon framework. The FCA exhibited good conductivity, high catalytic efficiency, and distinguished stability. When it was used as an electro-Fenton cathode, metalaxyl degradation results demonstrated that 98% TOC elimination was realized after 4 h, which was 1.5 times higher than that of the iron oxide supported electrode. It was attributed to self-doped Fe@Fe(2)O(3) ensuring Fe(II) as the mediator, maintaining high activity via reversibe oxidation and reduction by electron transfer among iron species with different valences. Meanwhile, an abundance of independent reaction microspaces were provided for every ferric crystal to in situ decompose electrogenerated H(2)O(2). Moreover, the possible catalytic mechanism was also proposed. The FCA was a promising candidate as potential cathode materials for high-performance electro-Fenton oxidation.

Selective photoelectrocatalytic degradation of recalcitrant contaminant driven by an n-P heterojunction nanoelectrode with molecular recognition ability.

With in situ molecular imprinting technique, a novel nanoelectrode (MI, n-P)-TiO(2) with n-P heterojunction and molecular recognition ability was fabricated by liquid phase deposition at low temperature. Using bisphenol A (BPA) as template, the spindle-like TiO(2) particles 40-80 nm in size compactly grew on the boron-doped diamond (BDD) substrate. Several spectroscopy measurements demonstrate that the BPA molecules were successfully imprinted on the TiO(2) matrix and numerous specific recognition sites to template were formed after calcination. The transient photocurrent response experiments have confirmed that the (MI, n-P)-TiO(2) nanoelectrode displays outstanding photoelectrocatalytic (PEC) activity and selectivity. The (MI, n-P)-TiO(2) is further employed in degrading the mixture containing BPA and interference 2-naphthol (2-NP). After 2 h, BPA removal reaches 97%, and corresponding kinetic constant is 1.76 h(-1), which is 4.6 times that of 2-NP removal even if 2-NP is much more concentrated. On the electrode without molecular imprint, the removal rate constants of BPA and 2-NP approximately equal, only about 0.5 h(-1). The results indicate that selective PEC oxidation can be realized readily on the (MI, n-P)-TiO(2) nanoelectrode due to the synergetic effects including strong recognition adsorption, formation of n-P heteojunction, and external electrostatic field. The effect of formation of n-P heterojunction on the enhanced PEC performances is also discussed.

Hydrothermally enhanced electrochemical oxidation of high concentration refractory perfluorooctanoic acid.

A green hydrothermally enhanced electrochemical oxidation (HTEO) technique is developed to treat the high concentration refractory perfluorooctanoic acid (PFOA) wastewater on boron-doped diamond (BDD) film electrode. Results show that HTEO can demonstrate higher degradation efficiency for PFOA than the normal electrochemical oxidation (EO) process, with the removal of PFOA, total organic carbon (TOC), and organic fluorine in the HTEO process increasing by 1.1, 1.8, and 2.1 times, respectively. The kinetics study indicates that the degradation of PFOA follows a first-order reaction in the HTEO process with the apparent reaction rate constant 3.1 times higher than that in the EO process. The higher degradation efficiency of PFOA is due to the hydrothermal enhancement in electrochemical properties of the electrode and solution. Compared with EO, during the HTEO process, the conductivity and ionic migration rate of the solution is improved by 540% and 60%, respectively. In addition, the Tafel slope is increased to 343 from 279 mV dec(-1), indicating an inhibition effect of oxygen evolution reaction and a more effective oxidation of PFOA. In particular, the hydrothermal condition promotes a high formation rate of hydroxyl radical with the concentration almost 2 times of that in EO, which is considered the inner factor leading to the higher degradation efficiency. The density functional theory simulations demonstrate that the nonterminal C-C bonds in the main carbon chain can be easily destructed in the hydrothermal condition, as confirmed by the experimental detection of intermediates of C(5)F(11)COOH, C(4)F(9)COOH, C(3)F(7)COOH, C(2)F(5)COOH, CF(3)COOH, and some dicarboxylic acids. As a result, a reaction pathway is tentatively proposed.

Selective Electrocatalytic Degradation of Odorous Mercaptans Derived from S–Au Bond Recongnition on a Dendritic Gold/Boron-Doped Diamond Composite Electrode

To improve selectivity of electrocatalytic degradation of toxic, odorous mercaptans, the fractal-structured dendritic Au/BDD (boron-doped diamond) anode with molecular recognition is fabricated through a facile replacement method. SEM and TEM characterizations show that the gold dendrites are single crystals and have high population of the Au (111) facet. The distinctive structure endows the electrode with advantages of low resistivity, high active surface area, and prominent electrocatalytic activity. To evaluate selectivity, the dendritic Au/BDD is applied in degrading two groups of synthetic wastewater containing thiophenol/2-mercaptobenzimidazole (targets) and phenol/2-hydroxybenzimidazole (interferences), respectively. Results show that targets removals reach 91%/94%, while interferences removals are only 58%/48% in a short time. The corresponding degradation kinetic constants of targets are 3.25 times and 4.1 times that of interferences in the same group, demonstrating modification of dendritic gold on BDD could effectively enhance electrocatalytic target-selectivity. XPS and EXAFS further reveal that the selective electrocatalytic degradation derives from preferential recognition and fast adsorption to thiophenol depending on strong Au-S bond. The efficient, selective degradation is attributed to the synergetic effects between accumulative behavior and outstanding electrochemical performances. This work provides a new strategy for selective electrochemical degradation of contaminants for actual wastewater treatment.