Investigation of electrocatalysts for CO_2 reduction to methane using gas-diffusion electrode and mechanism of enhanced activity

气体扩散电极CO_2还原制甲烷电催化剂及其增强活性机制研究

• 批准号: 09650778
• 负责人: KAWASHIMA Asahi
• 金额: $ 2.18万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650778/
• 关键词: electrochemical reduction of CO_2; formation of methane; amorphous alloys; electrocatalysis; gas diffusion electrode; 二酸化炭素還元; アモルファス合金電極

First of all, we have compared the steady state conventional potentiostatic method with pulsed method in the electrochemical reduction of CO_2. It was found that the faradaic efficiencies for the pulsed electroreduction ofCO_2 to methane and ethylene using copper electrode are higher than those for the potentiostatic reduction and more stable in a long-term electrolysis. In the next study, we have made various electrolysis from copper-based alloys and examined the faradaic efficiencies for methane and ethylene production from CO_2 reduction using pulsed electrolysis in CO_2 saturated 0.1 M KHCO_3 solution at room temperature. Amorphous Cu-Zr and Cu-Tialloy electrodes were prepared using a single-roller melt-spinning method. The sputtering method was applied to prepare Cu-Ag alloys. The amorphous Cu-(30, 40, 60)Zr and Cu-30Ti alloys showed considerably low faradaic efficiencies for methane and ethylene production and both efficiencies were less than 3 %. The sputter-deposited crystalline Cu-Ag alloy electrodes, when the alloys contain small amount of Ag (5-7at%), have a higher faradaic efficiency of methane in comparison with pure Cu electrode. However, excess amount of Ag was detrimental. Although methane and ethylene were not detected on pure Ag electrode, the efficiency of methane increased with the addition of a small amount of Cu but the efficiency was lower than that on pure Cu electrode. Next, gas-diffusion electrodes have been employed as the cathode. The gas-diffusion electrodes have been prepared from sputter-deposited Cu-Ag alloyed powder, carbon black powder and polytetrafluoroethylene dispersion. Thegas-diffusion electrode only made up of carbon black powder produced exclusively hydrogen gas. However, the Cu-Ag alloy powder-loaded gas-diffusion electrodes produced methane and ethylene and the total reduction current density was remarkably high, but their faradaic efficiencies were lower than those on the plate-type alloyelectrodes.

首先，我们比较了电化学还原CO_2时的稳态常规恒电位法与脉冲法。结果发现，铜电极脉冲电还原CO_2制甲烷和乙烯的法拉第效率高于恒电位还原法，且长期电解更稳定。在接下来的研究中，我们对铜基合金进行了各种电解，并检查了室温下在CO_2饱和0.1 M KHCO_3溶液中使用脉冲电解通过CO_2还原生产甲烷和乙烯的法拉第效率。采用单辊熔融纺丝法制备了非晶铜锆电极和铜钛合金电极。采用溅射法制备Cu-Ag合金。非晶态 Cu-(30,40,60)Zr 和 Cu-30Ti 合金在甲烷和乙烯生产方面表现出相当低的法拉第效率，并且两种效率均低于 3%。溅射沉积结晶铜银合金电极，当合金中含有少量银（5-7at%）时，与纯铜电极相比，具有更高的甲烷法拉第效率。然而，过量的Ag是有害的。虽然纯Ag电极上没有检测到甲烷和乙烯，但随着少量Cu的添加，甲烷的效率有所提高，但效率低于纯Cu电极。接下来，采用气体扩散电极作为阴极。气体扩散电极由溅射沉积铜银合金粉末、炭黑粉末和聚四氟乙烯分散体制备而成。仅由炭黑粉末制成的气体扩散电极仅产生氢气。然而，Cu-Ag合金粉末负载气体扩散电极产生甲烷和乙烯，总还原电流密度非常高，但其法拉第效率低于板式合金电极。