Preparation And Application Of LDH Modified Electrodes In Degradation Of Organic Pollutants

Chemically modified electrodes could reduce the active energy of electrochemicalreactions, and make the reactions selective. Generally speaking, these chemicallymodified electrodes are toxic to biomolecules, and could cause irreversible damage tobiomolecules. So, it becomes research focal point on chemically modified electrodes toprepare a kind of non-toxic electrodes with high efficiency. Biological nano-electrodesis just such a kind of electrodes. We used layered double hydroxides （LDH） to preparetwo kinds of biological nano-electrodes, LDH modified electrodes and in situ LDHelectrodes. In addition, muti-walls carbon nanotubes （MWNTs） were used as modifiedmaterials to research the non-toxicity and the electron transfer mechanism ofbiological nano-electrodes. The main contents include:1. NO₃-intercalated Mg-Al LDHs were prepared using coprecipitatin, and wereused to modify graphite electrodes. sodium dodecyl sulfate （SDS） and cellulose wereselected to investigated the immobilizing capability of LDH modified electrodes. X-raydiffraction （XRD）, infrared spectroscopy （IR） and scanning electron microscopy （SEM）were used to analyze the results. It is confirmed that LDH thin films attached firmly tographite electrodes, and kept its immobilizing capability. LDH modified electrodescould both absorb and exchange small molecules, but can only absorb big molecules.2. We investigated the direct electrochemistry of LDH modified electrodes to SDS,and the treatment efficiency to SDS containing simulating wastewater. Cyclicvoltammetry （CV） and uv-vis （UV） show that LDH could successfully oxidate SDS, theelectrode reaction is controlled by a diffusion-bound species. At the bestcondition（adsorbing for1h, electrolyte is2.0g/L of NaCl, pH10）, electrolysis for1h,SDS removal rate amounts to80.2%, and CODCr removal rate amounts to50.2.3. Mg-Al LDH thin films were fabricated in situ on Al support by a coprecipitationmethod, and we got the in situ LDH electrodes. This electrodes could successfullyoxidate NADH, and the electrode reaction is controlled by a diffusion-bound species.After soaked repeatedly and heated, it still shows LDH characteristic peaks and well crystallized, which explains the LDH thin films attached firmly to Al support. Smallmolecules can easily intercalate into LDH interlayers, but big molecules can onlyintercalate into LDH interlayers with the help of LDH.4. MWNTs were used to modify electrodes. We investigated the conformationalchanges of Cyt c from three levels when it interact with MWNTs, and how thesechanges improve electron transfer. The results explain that Cyt c go through changes ofsecondary structures, spatial orientation and Fe spin states. The three changes provideCyt c open activity center, the correct orientation and appreciate spin state for acceptingelectrons, finally realize electron transfer.