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Resolution of Electronic and Structural Factors Underlying Oxygen-Evolving Performance in Amorphous Cobalt Oxide Catalysts
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-07-20 , DOI: 10.1021/jacs.8b02719
Gihan Kwon , Hoyoung Jang 1 , Jun-Sik Lee 1 , Anil Mane , David J. Mandia , Sarah R. Soltau , Lisa M. Utschig , Alex B. F. Martinson , David M. Tiede , Hacksung Kim , Jungho Kim
Affiliation  

Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate domain building block, but differ significantly in OER performance that derives from different electron-proton charge transport properties. Here, we use a combination of L edge synchrotron X-ray absorption (XAS), resonant X-ray emission (RXES), resonant inelastic X-ray scattering (RIXS), resonant Raman (RR) scattering, and high-energy X-ray pair distribution function (PDF) analyses that identify electronic and structural factors correlated to the charge transport differences for CoPi and CoBi. The analyses show that CoBi is composed primarily of cobalt in octahedral coordination, whereas CoPi contains approximately 17% tetrahedral Co(II), with the remainder in octahedral coordination. Oxygen-mediated 4 p-3 d hybridization through Co-O-Co bonding was detected by RXES and the intersite dd excitation was observed by RIXS in CoBi, but not in CoPi. RR shows that CoBi resembles a disordered layered LiCoO2-like structure, whereas CoPi is amorphous. Distinct domain models in the nanometer range for CoBi and CoPi have been proposed on the basis of the PDF analysis coupled to XAS data. The observed differences provide information on electronic and structural factors that enhance oxygen evolving catalysis performance.

中文翻译:

解析无定形钴氧化物催化剂中析氧性能的电子和结构因素

非贵金属薄膜氧化物作为析氧反应 (OER) 的有前途的催化剂被广泛研究。在硼酸盐 (CoBi) 和磷酸盐 (CoPi) 存在下电化学形成的无定形氧化钴薄膜具有共同的钴酸盐域构建块,但由于不同的电子-质子电荷传输特性,其 OER 性能存在显着差异。在这里,我们结合使用 L 边缘同步加速器 X 射线吸收 (XAS)、共振 X 射线发射 (RXES)、共振非弹性 X 射线散射 (RIXS)、共振拉曼 (RR) 散射和高能 X-射线对分布函数 (PDF) 分析可识别与 CoPi 和 CoBi 的电荷传输差异相关的电子和结构因素。分析表明 CoBi 主要由八面体配位的钴组成,而 CoPi 包含大约 17% 的四面体 Co(II),其余为八面体配位。RXES 检测到氧介导的通过 Co-O-Co 键合的 4 p-3 d 杂交,RIXS 在 CoBi 中观察到位点间 dd 激发,但在 CoPi 中未观察到。RR 显示 CoBi 类似于无序的层状 LiCoO2 状结构,而 CoPi 是无定形的。基于与 XAS 数据耦合的 PDF 分析,已经提出了 CoBi 和 CoPi 在纳米范围内的不同域模型。观察到的差异提供了有关增强析氧催化性能的电子和结构因素的信息。RXES 检测到氧介导的通过 Co-O-Co 键合的 4 p-3 d 杂交,RIXS 在 CoBi 中观察到位点间 dd 激发,但在 CoPi 中未观察到。RR 显示 CoBi 类似于无序的层状 LiCoO2 状结构,而 CoPi 是无定形的。基于与 XAS 数据耦合的 PDF 分析,已经提出了 CoBi 和 CoPi 在纳米范围内的不同域模型。观察到的差异提供了有关增强析氧催化性能的电子和结构因素的信息。RXES 检测到氧介导的通过 Co-O-Co 键合的 4 p-3 d 杂交,RIXS 在 CoBi 中观察到位点间 dd 激发,但在 CoPi 中未观察到。RR 显示 CoBi 类似于无序的层状 LiCoO2 状结构,而 CoPi 是无定形的。基于与 XAS 数据耦合的 PDF 分析,已经提出了 CoBi 和 CoPi 在纳米范围内的不同域模型。观察到的差异提供了有关增强析氧催化性能的电子和结构因素的信息。
更新日期:2018-07-20
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