Development of Environmental Catalytic Reactors Based on Electrochemical Acceleration

利用电化学池在70℃的条件下成功地实现了过量氧存在下NOx的还原。H+导电固体聚合物电解质(SPE)在铂阴极上催化NO-H_2反应生成氢，生成Ca+C_476。结果表明，在进气过程中，铂阴极上电化学生成的氢对NO的催化活性高于H_2分子。由于铂表面覆盖了稳定的硝酸盐(NO3)物种，阻碍了氧在铂表面的吸附，从而抑制了H_2-O_2竞争反应。固相萃取电池与负载型铂催化剂的结合可广泛应用于新型低温脱氮工艺。在Nafion-117H~(++)导电聚合物膜上沉积的铜-钯和铜-铂双金属阴极也被用于硝酸根离子(NO3)的电催化还原。通过在膜-电极组件(MEA)上施加直流电流，阴极上析出的H_2导致阴极室中NO_3~-的单调降解。这个。NO_3~-还原是连续进行的，铜显著提高了催化剂第一步从NO_3~-到NO_2~-的催化活性。当铜含量分别为38at%和20at%时，铜-钯和铜-铂阴极的还原速率最高。产物选择性还依赖于铜的含量。由于对NO_2还原的催化活性较高，铜-钯阴极对NO_2~(2+)的选择性较低，对NH_4~+的选择性较高。添加CO_2可以提高硝酸盐还原速率，起到缓冲作用，使pH值保持在7以下，改变反应的平衡状态，即2NO_3+5H_2+N_2+2OH^-+4H_2O。

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.