Yang Bo, Yu Gang, Huang Jun
Department of Environmental Science and Engineering, POPs Research Centre, Tsinghua University, Beijing 100084, China.
Environ Sci Technol. 2007 Nov 1;41(21):7503-8. doi: 10.1021/es071168o.
Palladium-modified materials have been found to be effective electrodes for the reductive degradation of chlorinated compounds in aqueous solution. This study investigated the electrocatalytic hydrodechlorination (ECH) of polychlorinated biphenyls (PCBs) in solvent/surfactant-aided solutions in a palladium-modified nickel foam electrode using a divided flow-through cell. The reaction pathways of 2,4,5-PCB hydrodechlorination were proposed due to the analysis of intermediates by GC/MS. The mechanism of electrocatalytic reaction on the Pd/Ni foam cathode was examined by studying the effect of surfactant type, sorption behavior of PCBs on the electrode, and current densities on the ECH efficiency of PCBs. The conversion of PCBs was controlled by the micelle structures of the surfactants instead of the charged species. According to the analysis of hydrogen transformation processes on the electrode surface, we propose that the ECH process was initiated by the transfer of highly active hydrogen atoms [H] from the prior polarized Pd particles to the less polarized Pd particles by spillover on the Pd/Ni foam cathode. Therefore, the total available surface was larger than the originally polarized surface, and [H] could smoothly react with PCBs that were adsorbed on the surface. As a result, a high ECH efficiency can be achieved with the Pd/Ni foam electrode.
钯改性材料已被发现是用于水溶液中氯化化合物还原降解的有效电极。本研究使用分流式流通池，在钯改性泡沫镍电极的溶剂/表面活性剂辅助溶液中研究了多氯联苯（PCBs）的电催化加氢脱氯（ECH）。通过气相色谱/质谱联用仪（GC/MS）对中间体进行分析，提出了2,4,5-多氯联苯加氢脱氯的反应途径。通过研究表面活性剂类型、多氯联苯在电极上的吸附行为以及电流密度对多氯联苯电催化加氢脱氯效率的影响，考察了泡沫镍阴极上的电催化反应机理。多氯联苯的转化受表面活性剂的胶束结构而非带电物种的控制。根据对电极表面氢转化过程的分析，我们提出电催化加氢脱氯过程是由高活性氢原子[H]通过在泡沫镍阴极上的溢流作用，从预先极化的钯颗粒转移到极化程度较低的钯颗粒而引发的。因此，总的可用表面大于最初极化的表面，并且[H]可以与吸附在表面的多氯联苯顺利反应。结果，使用泡沫镍电极可以实现较高的电催化加氢脱氯效率。
