Selectivity of Reduction Products of Carbon Dioxides by Pulsed Electrolysis

本研究的目的是：(1)获得二氧化碳还原产物的选择性；(2)开发一种保护长期电解过程中电极降解的新技术。本文提出的方法是采用脉冲电解的方法，通过选择阳极偏置V_a和阴极偏置V_c及其持续时间T_a和T_c来获得最佳的实验条件。上述项目目标已基本实现。还原产物的选择性：Cu电极：优化阳极偏压可以提高甲烷和乙烯制氢的相对产率。阳极偏压也会改变甲烷制乙烯的相对产率。银电极：已知这种电极主要产生一氧化碳，作为二氧化碳在电位/电流静态电解下的还原产物。然而，在脉冲法中，在优化的偏置条件下也可以产生甲烷和乙烯。此外，在不同的阳极偏压下也可以生产乙醇，而不是以CH_4和C_2H_4为主。电极稳定性：长期电解不会使电极退化，也不会降低电极反应的选择性。

The objective of the present research is (1) to obtain the selectivity of reduction products of carbon dioxides and (2) to develop a new technique for protecting the degradation of electrodes taking place during long-term electrolysis. The proposed technique is to use pulsed electrolysis in which the following four parameters can be chosen to obtain optimum experimental condition : anodic bias V_a and cathodic bias V_c and their durations T_a and T_c. Project goal mentioned above has been almost fully attained.The selectivity of reduction products :Cu electrodes : Relative yields of methane and ethylene to hydrogen could be increased by optimizing the anodic bias. Relative yields of methane to ethylene could be also changed by anodic bias.Ag electrodes : This electrode is known to predominantly produce carbon monooxide as a reduction product of carbon dioxides under a potentio/galvano static electrolysis. In the pulsed method, however, methane and ethylene can be also produced under optimized bias conditions. In addition, ethanol can be also produced at different anodic bias from that at which CH_4 and C_2H_4 are predominantly produced.Stability of electrodes :Long term electrolysis could be performed without any degradation of electrodes as well as without deterioration of the selectivity of electrode reaction.