Seo Hongmin, Park Sunghak, Cho Kang Hee, Choi Seungwoo, Ko Changwan, Randriamahazaka Hyacinthe, Nam Ki Tae
Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
Nano System Institute, Seoul National University, Seoul 08826, Republic of Korea.
ACS Omega. 2021 Jul 6;6(28):18404-18413. doi: 10.1021/acsomega.1c02397. eCollection 2021 Jul 20.
The development of efficient water-oxidizing electrocatalysts is a key issue for achieving high performance in the overall water electrolysis technique. However, the complexity of multiple electron transfer processes and large activation energies have been regarded as major bottlenecks for efficient water electrolysis. Thus, complete electrochemical processes, including electron transport, charge accumulation, and chemical bond formation/dissociation, need to be analyzed for establishing a design rule for film-type electrocatalysts. In light of this, complex capacitance analysis is an effective tool for investigating the charge accumulation and dissipation processes of film-type electrocatalysts. Here, we conduct complex capacitance analysis for the MnO nanocatalyst, which exhibits superb catalytic activity for water oxidation under neutral conditions. Charge was accumulated on the catalyst surface by the change in Mn valence between Mn(II) and Mn(IV) prior to the rate-determining O-O bond forming step. Furthermore, we newly propose the dissipation ratio () for understanding the energy balance between charge accumulation and charge consumption for chemical O-O bond formation. From this analysis, we reveal the potential- and thickness-dependent contribution of the charge accumulation process on the overall catalytic efficiency. We think that an understanding of complex capacitance analysis could be an effective methodology for investigating the charge accumulation process on the surface of general film-type electrocatalysts.
开发高效的析氧电催化剂是在整体水电解技术中实现高性能的关键问题。然而，多电子转移过程的复杂性和高活化能被视为高效水电解的主要瓶颈。因此，为了建立薄膜型电催化剂的设计规则，需要分析包括电子传输、电荷积累以及化学键形成/解离在内的完整电化学过程。鉴于此，复电容分析是研究薄膜型电催化剂电荷积累和耗散过程的有效工具。在此，我们对MnO纳米催化剂进行复电容分析，该催化剂在中性条件下对水氧化表现出卓越的催化活性。在决定反应速率的O - O键形成步骤之前，通过Mn（II）和Mn（IV）之间的Mn价态变化，电荷在催化剂表面积累。此外，我们新提出了耗散率（），以理解电荷积累与化学O - O键形成的电荷消耗之间的能量平衡。通过该分析，我们揭示了电荷积累过程对整体催化效率的电位和厚度依赖性贡献。我们认为，理解复电容分析可能是研究一般薄膜型电催化剂表面电荷积累过程的有效方法。
