Impacts of electrode potentials and solvents on the electroreduction of CO2: a comparison of theoretical approaches.
Impacts of electrode potentials and solvents on the electroreduction of CO2: a comparison of theoretical approaches.
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DOI：
10.1039/c5cp00946d
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发表时间：
2015-05
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影响因子：
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通讯作者：
S. Steinmann;C. Michel;R. Schwiedernoch;P. Sautet
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文献类型：
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作者：
S. Steinmann;C. Michel;R. Schwiedernoch;P. Sautet
由于CO2是全世界容易获得的原料，因此利用CO2作为合成有价值的化学品的C1结构单元是一个非常有吸引力的概念。然而，由于其能量耗尽的“碳汇”的性质，CO2具有非常低的反应性。电催化提供了通过还原活化CO2的最有吸引力的方法：电子是“最清洁”的还原剂，其能量可以调节到热力学最佳值。在质子条件下，CO2在许多金属电极上的还原导致甲酸。因此，为了开辟其用作C1结构单元的道路，应避免水的存在以允许更多样化的化学反应，特别是用于与烯烃形成C-C键。在这些条件下，CO2的固有反应性可以通过C-O和C-C键的形成分别生成碳酸酯和碳酸酯。在Ni（111）上，实验证明几乎只有碳酸盐和一氧化碳。尽管最近在模拟电催化反应方面取得了进展，但确定竞争反应途径之间的实际机制和选择性仍然不是直截了当的。作为一个简单但重要的例子，CO2在非质子条件下的固有反应性，我们强调的缺点流行的线性自由能关系电极电位（LFER-EP）。通过对表面充电，从而明确地将电化学势包括在电子结构计算中，从而超越这种零阶近似，使我们能够获得更详细的见解，揭示覆盖效应和抗衡离子的影响。
Since CO2 is a readily available feedstock throughout the world, the utilization of CO2 as a C1 building block for the synthesis of valuable chemicals is a highly attractive concept. However, due to its very nature of energy depleted "carbon sink", CO2 has a very low reactivity. Electrocatalysis offers the most attractive means to activate CO2 through reduction: the electron is the "cleanest" reducing agent whose energy can be tuned to the thermodynamic optimum. Under protic conditions, the reduction of CO2 over many metal electrodes results in formic acid. Thus, to open the road to its utilization as a C1 building block, the presence of water should be avoided to allow a more diverse chemistry, in particular for C-C bond formation with alkenes. Under those conditions, the intrinsic reactivity of CO2 can generate carbonates and oxalates by C-O and C-C bond formation, respectively. On Ni(111), almost exclusively carbonates and carbon monoxide are evidenced experimentally. Despite recent progress in modelling electrocatalytic reactions, determining the actual mechanism and selectivities between competing reaction pathways is still not straight forward. As a simple but important example of the intrinsic reactivity of CO2 under aprotic conditions, we highlight the shortcomings of the popular linear free energy relationship for electrode potentials (LFER-EP). Going beyond this zeroth order approximation by charging the surface and thus explicitly including the electrochemical potential into the electronic structure computations allows us to access more detailed insights, shedding light on coverage effects and on the influence of counterions.