Origin of the N-coordinated single-atom Ni sites in heterogeneous electrocatalysts for CO2 reduction reaction,Chemical Science

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Origin of the N-coordinated single-atom Ni sites in heterogeneous electrocatalysts for CO2 reduction reaction
Chemical Science ( IF 7.6 ) Pub Date : 2021-10-07 , DOI: 10.1039/d1sc04094d
Yu Wang ₁ , Liming You ₁ , Kun Zhou _{1,

2}

Affiliation

Heterogeneous Ni–N–C single-atom catalysts (SACs) have attracted great research interest regarding their capability in facilitating the CO₂ reduction reaction (CO₂RR), with CO accounting for the major product. However, the fundamental nature of their active Ni sites remains controversial, since the typically proposed pyridinic-type Ni configurations are inactive, display low selectivity, and/or possess an unfavorable formation energy. Herein, we present a constant-potential first-principles and microkinetic model to study the CO₂RR at a solid–water interface, which shows that the electrode potential is crucial for governing CO₂ activation. A formation energy analysis on several NiN_xC_4−x (x = 1–4) moieties indicates that the predominant Ni moieties of Ni–N–C SACs are expected to have a formula of NiN₄. After determining the potential-dependent thermodynamic and kinetic energy of these Ni moieties, we discover that the energetically favorable pyrrolic-type NiN₄ moiety displays high activity for facilitating the selective CO₂RR over the competing H₂ evolution. Moreover, model polarization curves and Tafel analysis results exhibit reasonable agreement with existing experimental data. This work highlights the intrinsic tetrapyrrolic coordination of Ni for facilitating the CO₂RR and offers practical guidance for the rational improvement of SACs, and this model can be expanded to explore mechanisms of other electrocatalysis in aqueous solutions.

中文翻译：

CO2还原反应多相电催化剂中N配位单原子Ni位点的起源

非均相Ni-N-C单原子催化剂（SAC）因其促进CO ₂还原反应（CO ₂ RR）的能力而引起了人们极大的研究兴趣，其中CO是主要产物。然而，其活性镍位点的基本性质仍然存在争议，因为通常提出的吡啶型镍构型是不活泼的，表现出低选择性，和/或具有不利的形成能。在此，我们提出了恒电位第一原理和微动力学模型来研究固水界面上的CO _{2 RR，这表明电极电位对于控制CO}₂活化至关重要。_{对几个 NiN x} C _{4− x} ( x = 1–4) 部分的形成能分析表明 Ni-N-C SAC 的主要 Ni 部分预计具有 NiN ₄的分子式。在确定这些Ni部分的电势依赖性热力学和动能后，我们发现能量上有利的吡咯型NiN ₄部分表现出高活性，有利于选择性CO ₂ RR而不是竞争性H ₂析出。此外，模型极化曲线和塔菲尔分析结果与现有实验数据表现出合理的一致性。这项工作突出了Ni内在的四吡咯配位促进CO ₂ RR的作用，为SAC的合理改进提供了实践指导，并且该模型可以扩展到探索水溶液中其他电催化的机制。

更新日期：2021-10-13

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