Ou Lihui, Jin Junling, Chen Yuandao
Hunan Province Cooperative Innovation Center for the Construction & Development of Dongting Lake Ecologic Economic Zone, Hunan Provincial Key Laboratory of Water Treatment Functional Materials, Hunan Province Engineering Research Center of Electroplating Wastewater Reuse Technology, College of Chemistry and Materials Engineering, Hunan University of Arts and Science Changde 415000 China
RSC Adv. 2021 May 17;11(29):17828-17839. doi: 10.1039/d1ra01978c. eCollection 2021 May 13.
An improved H coverage-dependent Au(111)/HO electrochemical interface model is proposed in this paper, which is firstly used to study electroreduction mechanisms of N into NH at the thermodynamical equilibrium potential in cooperation with electronic structure analysis. The results show that the associative mechanism is more favorable on Au(111) and therein alternating and distal pathways may be able to parallelly occur in gas phase and the present simulated electrochemical interface. The initial N reduction into the NH intermediate is the rate determining step, which may be able to be regarded as the origin of the observed experimentally high overpotential during N electroreduction. The presence of an electrochemical environment can significantly change the N reduction pathway and decrease the barrier of the rate determining step, which can be ascribed to the significant electron accumulation and interaction between N molecules and HO clusters. The theoretical results display excellent consistency with the available experimental data, confirming the rationality of the present proposed electrochemical model. The comparison of the barrier between the hydrogen evolution reaction and rate determining step well explains why the activity of Au electrodes is usually unsatisfactory. Accordingly, a single descriptor can be proposed, in which an ideal electrocatalyst should be able to reduce the barrier for initial N electroreduction into NH. In this way, N electroreduction pathways can be facilitated and the yield of NH can be enhanced. We believe that the present study can represent progress to study N electroreduction mechanisms from an improved electrochemical model.
本文提出了一种改进的与氢覆盖度相关的Au(111)/HO电化学界面模型，该模型首次用于结合电子结构分析研究在热力学平衡电位下氮电还原为氨的机理。结果表明，缔合机理在Au(111)上更有利，在气相和当前模拟的电化学界面中，交替和远端途径可能会并行发生。氮最初还原为NH中间体是速率决定步骤，这可以被视为在氮电还原过程中实验观察到的高过电位的起源。电化学环境的存在可以显著改变氮的还原途径并降低速率决定步骤的能垒，这可归因于氮分子与HO团簇之间显著的电子积累和相互作用。理论结果与现有实验数据显示出极好的一致性，证实了本文提出的电化学模型的合理性。析氢反应与速率决定步骤之间能垒的比较很好地解释了为什么金电极的活性通常不尽人意。因此，可以提出一个单一的描述符，其中理想的电催化剂应该能够降低氮最初电还原为NH的能垒。通过这种方式，可以促进氮的电还原途径并提高氨的产率。我们相信，本研究能够代表从改进的电化学模型研究氮电还原机理方面取得的进展。
