Development of Environmental Catalytic Reactors Based on Electrochemical Acceleration

在70℃下，用电化学方法成功地实现了过量O_2存在下NO_x的还原。H+导电固体聚合物电解质（SPE）利用催化NO-H_2反应在Pt阴极上向ca+ C476产生氢气。结果表明，Pt阴极上的电化学析氢比原料气中的H_2分子对NO的反应活性更高。由于Pt表面被稳定的硝酸根（NO_3）覆盖，阻碍了氧在Pt表面的吸附，从而抑制了H_2-O_2的竞争反应。SPE电池与负载型Pt催化剂的结合可广泛应用于新型低温脱硝工艺。在Nafion-117 H^+导电聚合物膜上制备的Cu-Pd和Cu-Pt双金属阴极上，也进行了硝酸根离子（NO_3）的电催化还原。通过对膜电极组件（MEA）施加直流电，H_2在阴极上析出，导致NO_3^-在阴极室中单调降解。的. NO_3^-还原反应是连续进行的，Cu显著提高了NO_3^-还原为NO_2^-的第一步催化活性。分别具有38和20原子% Cu的Cu-Pd和Cu-Pt阴极表现出最高的还原速率。产物的选择性也取决于Cu的含量。Cu-Pd阴极对NO_2的还原活性高，对NO_2^-的选择性低，对NH_4^+的选择性高。CO_2的加入使硝酸盐还原反应的pH值降低到7以下，并使反应平衡2NO_3 + 5H_2 + N_2 + 2 OH ^- + 4H_2O发生移动，从而加快了硝酸盐还原反应的速率。

The reduction of NO_x, in the presence of excess O_2 has been successfully achieved at 70℃ using an electrochemical cell. An H+-conducting solid polymer electrolyte(SPE)yielded hydrogen on the Pt cathode to ca+C476use the catalytic NO-H_2 reaction. It was revealed that the electrochemically evolved hydrogen on the Pt cathode is more active toward NO than molecular H_2 in the gas feed. The competitive H_2-O_2 reaction is suppressed because the Pt surface is covered with stable nitrate(NO_3)species, which blocks oxygen adsorption hereon. The combination between the SPE cell and supported Pt catalysts can broadly be applied to novel low-temperature de-NO_x processes. Electrocatalytic reduction of nitrate ions(NO_3)was also carried out over Cu-Pd and Cu-Pt bimetallic cathodes, which were deposited on a Nafion-117 H^+-conducting polymer membrane. By applying DC current to the membrane-electrode assembly(MEA), H_2 evolved on the cathode caused monotonic degradation of NO_3^- in the cathode compartment. The. NO_3^- reduction proceeded in a consecutive manner and copper increased significantly the catalytic activity for the first step from NO_3^- to NO_2^-. The Cu-Pd and Cu-Pt cathodes, having 38 and 20 at% Cu, respectively, exhibited the highest reduction rate. The product selectivity was also dependant on the content of Cu. The Cu-Pd cathode showed a lower selectivity to NO_2^- and a higher selectivity to NH_4^+, because the catalytic activity for NO_2 reduction is high. The rate of nitrate reduction was increased by supplying CO_2, which plays a role of a buffer to keep pH lower than 7 and shift the equilibrium of the reaction, 2NO_3 + 5H_2 + N_2 + 2OH^- + 4H_2O.