Abstract:

Gas diffusion electrode can enhance mass transfer of CO₂ for CO₂ electrochemical reduction. A carbon felt loaded Sn-graphene gas diffusion electrode for electrochemical reduction of CO₂ to formic acid. Effects of CO₂ reaction condition,electrode thickness,Sn loading and electrolytic potential were studied. The results showed that the performance of CO₂ electrochemical reduction was better under the gas phase CO₂ reaction condition than that under dissolved CO₂ condition. Increasing the electrode thickness or Sn loading within an appropriate range led to an improvement in electrochemical reduction of carbon dioxide to formic acid due to the increase in the gas-liquid-solid three-phase interface. The production of formic acid was raised with the negative shift of the electrolytic potential,while the Faraday efficiency increased at first and then decreased. The average current density of (12.79±1.27)mA·cm^-2 and highest Faraday efficiency of 41.55%±2.50% for electrochemical reduction of carbon dioxide to formic acid were obtained at -1.8 V (vs Ag/AgCl) using the carbon felt electrode with the electrode thickness of 5 mm and Sn loading of 5 mg·cm^-2.

Key words: carbon dioxide, reduction, porous media, carbon felt electrode, catalyst loading, electrolytic potential

摘要：

针对CO₂电化学还原中气体扩散电极可强化CO₂的传质，基于碳毡制备了负载锡-石墨烯催化层的新型气体扩散电极，研究了CO₂反应条件、电极厚度、催化剂载量及反应电位对CO₂电化学还原性能的影响。实验结果表明：与溶解态CO₂反应条件相比，采用气相CO₂反应条件电化学还原性能更好；一定范围内增加电极厚度和催化剂载量可以增加气-液-固三相反应界面，提升CO₂电化学还原性能；随着电解电位负移，甲酸产量增加，电流效率先增大后减小；实验中使用厚度为5 mm、载量为5 mg·cm^-2的电极，在-1.8 V（vs Ag/AgCl）条件下进行电化学还原时，平均电流密度为（12.79±1.27） mA·cm^-2，甲酸电流效率达到最佳为41.55%±2.50%。

关键词: 二氧化碳, 还原, 多孔介质, 碳毡电极, 催化剂载量, 电解电位