Wang Xue, Xu Aoni, Li Fengwang, Hung Sung-Fu, Nam Dae-Hyun, Gabardo Christine M, Wang Ziyun, Xu Yi, Ozden Adnan, Rasouli Armin Sedighian, Ip Alexander H, Sinton David, Sargent Edward H
Department of Electrical and Computer Engineering , University of Toronto , 35 St. George Street , Toronto , Ontario M5S 1A4 , Canada.
Department of Mechanical and Industrial Engineering , University of Toronto , 5 King's College Road , Toronto , Ontario M5S 3G8 , Canada.
J Am Chem Soc. 2020 Feb 19;142(7):3525-3531. doi: 10.1021/jacs.9b12445. Epub 2020 Feb 4.
The electroreduction of carbon dioxide (CORR) to valuable chemicals is a promising avenue for the storage of intermittent renewable electricity. Renewable methane, obtained via CORR using renewable electricity as energy input, has the potential to serve as a carbon-neutral fuel or chemical feedstock, and it is of particular interest in view of the well-established infrastructure for its storage, distribution, and utilization. However, CORR to methane still suffers from low selectivity at commercially relevant current densities (>100 mA cm). Density functional theory calculations herein reveal that lowering *CO coverage on the Cu surface decreases the coverage of the *CO intermediate, and then this favors the protonation of *CO to *CHO, a key intermediate for methane generation, compared to the competing step, C-C coupling. We therefore pursue an experimental strategy wherein we control local CO availability on a Cu catalyst by tuning the concentration of CO in the gas stream and regulate the reaction rate through the current density. We achieve as a result a methane Faradaic efficiency (FE) of (48 ± 2)% with a partial current density of (108 ± 5) mA cm and a methane cathodic energy efficiency of 20% using a dilute CO gas stream. We report stable methane electrosynthesis for 22 h. These findings offer routes to produce methane with high FE and high conversion rate in CORR and also make direct use of dilute CO feedstocks.
将二氧化碳电还原（CORR）为有价值的化学品是储存间歇性可再生电力的一条有前景的途径。通过使用可再生电力作为能量输入的CORR获得的可再生甲烷，有潜力用作碳中性燃料或化学原料，鉴于其储存、运输和利用的成熟基础设施，它尤其受到关注。然而，在商业相关电流密度（>100 mA cm）下，CORR制甲烷仍存在选择性低的问题。本文的密度泛函理论计算表明，降低铜表面的CO覆盖率会降低CO中间体的覆盖率，进而与竞争步骤C-C偶联相比，这有利于CO质子化为CHO，*CHO是生成甲烷的关键中间体。因此，我们采用一种实验策略，即通过调节气流中CO的浓度来控制铜催化剂上局部CO的可用性，并通过电流密度来调节反应速率。结果，使用稀释的CO气流，我们实现了甲烷法拉第效率（FE）为（48±2）%，分电流密度为（108±5）mA cm，甲烷阴极能量效率为20%。我们报告了22小时的稳定甲烷电合成。这些发现为在CORR中以高FE和高转化率生产甲烷提供了途径，并且还能直接利用稀释的CO原料。
