Electrolyte-Dependent Oxygen Evolution Reactions in Alkaline Media: Electrical Double Layer and Interfacial Interactions
Electrolyte-Dependent Oxygen Evolution Reactions in Alkaline Media: Electrical Double Layer and Interfacial Interactions
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DOI：
10.1021/acsami.9b06889
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发表时间：
2019-09-18
影响因子：
9.5
通讯作者：
Chuang, Po-Ya Abel
中科院分区：
文献类型：
--
作者：
Li, Guang-Fu;Divinagracia, Maricor;Chuang, Po-Ya Abel
电催化反应的传统理解通常集中在吸附物和反应界面之间的共价相互作用（即，电双层，EDL）或电解质离子之间的静电相互作用。在这里，我们的工作提供了有价值的见解界面结构和碱性析氧反应（OER）过程中的离子相互作用。证明了内球OH-吸附的重要性，因为IrOx活性在4.0 M KOH中比在0.1 M KOH中高6.5倍。添加NaNO 3作为支持电解质，其被发现对于长期稳定性是惰性的，使半电池中的电催化反应复杂化。Na+在致密界面层外的非特异性吸附比K+与OH-通过氢键形成更强的非共价相互作用，导致界面OH-迁移率降低。这一假说强调了外层吸附对OER的重要性，OER通常被认为是一个纯粹的内层过程。同时，根据我们的实验观察，固态氧化还原的赝电容行为可能是更可靠的定量活性位点的OER比从传统的EDL充电电容过程中测量。观察到的界面氧传输，以提高电解质的电导率，归因于增加可访问的活性位点。耐久性导致液体碱性电解槽，这表明向KOH溶液中添加NaNO 3导致OER活性和长期稳定性的额外降低。这些发现提供了一个更好的理解的机制的细节和结构图案所需的高效和强大的电催化。
Traditional understanding of electrocatalytic reactions generally focuses on either covalent interactions between adsorbates and the reaction interface (i.e., electrical double layer, EDL) or electrostatic interactions between electrolyte ions. Here, our work provides valuable insights into interfacial structure and ionic interactions during alkaline oxygen evolution reaction (OER). The importance of inner-sphere OH- adsorption is demonstrated as the IrOx activity in 4.0 M KOH is 6.5 times higher than that in 0.1 M KOH. Adding NaNO3 as a supporting electrolyte, which is found to be inert for long-term stability, complicates the electrocatalytic reaction in a half cell. The nonspecially adsorbed Na+ in the outer compact interfacial layer is suggested to form a stronger noncovalent interaction with OH- through hydrogen bond than adsorbed K+, leading to the decrease of interfacial OH- mobility. This hypothesis highlights the importance of outer-sphere adsorption for the OER, which is generally recognized as a pure inner-sphere process. Meanwhile, based on our experimental observations, the pseudocapacitive behavior of solid-state redox might be more reliable in quantifying active sites for OER than that measured from the conventional EDL charging capacitive process. The interfacial oxygen transport is observed to improve with increasing electrolyte conductivity, ascribing to the increased accessible active sites. The durability results in a liquid alkaline electrolyzer which shows that adding NaNO3 into KOH solution leads to additional degradation of OER activity and long-term stability. These findings provide an improved understanding of the mechanistic details and structural motifs required for efficient and robust electrocatalysis.