Lin Yangming, Wu Kuang-Hsu, Lu Qing, Gu Qingqing, Zhang Liyun, Zhang Bingsen, Su Dangsheng, Plodinec Milivoj, Schlögl Robert, Heumann Saskia
Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36 , Mülheim an der Ruhr 45470 , Germany.
School of Chemical Engineering , The University of New South Wales , Sydney , Kensington, New South Wales 2052 , Australia.
J Am Chem Soc. 2018 Nov 7;140(44):14717-14724. doi: 10.1021/jacs.8b07627. Epub 2018 Oct 25.
Nanocarbon can promote robust and efficient electrocatalytic water oxidation through active surface oxygen moieties. The recent mechanistic understandings (e.g., active sites) of metal-free carbon catalysts in oxygen evolution reaction (OER), however, are still rife with controversies. In this work, we describe a facile protocol in which eight kinds of aromatic molecules with designated single oxygen species were used as model structures to investigate the explicit roles of each common oxygen group in OER at a molecular level. These model structures were decorated onto typical nanocarbon surfaces like onion-like carbons (OLC) or multiwalled carbon nanotubes (MWCNT) to build aromatic molecule-modified carbon systems. We show that edge (including zigzag and armchair) quinones in a conjugated π network are the true active centers, and the roles of ether and carboxyl groups are excluded in the OER process. The plausible rate-determining step could be singled out by H/D kinetic isotope effects. The turnover frequency per C═O (∼0.323 s at η = 340 mV) in 0.1 M KOH and the optimized current density (10 mA/cm at 1.58 V vs RHE) of quinone-modified carbon systems are comparable to those of promising metal-based catalysts.
纳米碳可以通过活性表面氧部分促进强劲且高效的电催化水氧化。然而，目前对于析氧反应（OER）中无金属碳催化剂的机理理解（例如活性位点）仍存在诸多争议。在这项工作中，我们描述了一种简便的方法，其中使用八种具有特定单氧物种的芳香族分子作为模型结构，在分子水平上研究每个常见氧基团在OER中的具体作用。这些模型结构被修饰到典型的纳米碳表面，如洋葱状碳（OLC）或多壁碳纳米管（MWCNT）上，以构建芳香族分子修饰的碳体系。我们表明，共轭π网络中的边缘（包括锯齿形和扶手椅形）醌是真正的活性中心，并且醚基和羧基在OER过程中的作用被排除。通过H/D动力学同位素效应可以确定可能的速率决定步骤。醌修饰的碳体系在0.1 M KOH中的每C═O周转频率（在η = 340 mV时约为0.323 s）和优化的电流密度（相对于RHE在1.58 V时为10 mA/cm）与有前景的金属基催化剂相当。
