Development of Environmental Catalytic Reactors Based on Electrochemical Acceleration

在70℃条件下，利用电化学电池成功地实现了过量O_2存在下NO_x的还原。一种H+导电固体聚合物电解质（SPE）通过催化NO-H_2反应在Pt阴极上生成ca+ c476。结果表明，Pt阴极上电化学生成的氢比进气中的H_2分子对NO更有活性。由于Pt表面覆盖了稳定的硝酸（NO_3）物质，阻碍了Pt表面对氧的吸附，从而抑制了H_2-O_2的竞争性反应。SPE电池与负载Pt催化剂的结合可以广泛应用于新型低温脱硝工艺。硝酸离子（NO_3）在Cu-Pd和Cu-Pt双金属阴极上进行了电催化还原，这两种阴极沉积在nation -117 H^+导电聚合物膜上。在膜电极组件（MEA）上施加直流电流，H_2在阴极上扩散，引起阴极室NO_3^-的单调降解。这个。NO_3^-的还原是连续进行的，铜显著提高了NO_3^-到NO_2^-第一步的催化活性。Cu- pd和Cu- pt阴极的还原率最高，分别为38%和20%。产物选择性也与Cu的含量有关。Cu-Pd阴极对NO_2^-有较低的选择性，对NH_4^+有较高的选择性，因为其对NO_2还原的催化活性较高。CO_2作为缓冲剂，使pH值保持在7以下，改变了2NO_3 + 5H_2 + N_2 + 2OH^- + 4H_2O的反应平衡，提高了硝酸还原速率。

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.