Kwon Gihan, Kokhan Oleksandr, Han Ali, Chapman Karena W, Chupas Peter J, Du Pingwu, Tiede David M
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave, Lemont, IL 60439, USA.
Department of Materials Science and Engineering, University of Science and Technology of China, 96 Jinzhai Rd, Hefei 230026, People's Republic of China.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2015 Dec 1;71(Pt 6):713-21. doi: 10.1107/S2052520615022180.
Amorphous thin film oxygen evolving catalysts, OECs, of first-row transition metals show promise to serve as self-assembling photoanode materials in solar-driven, photoelectrochemical `artificial leaf' devices. This report demonstrates the ability to use high-energy X-ray scattering and atomic pair distribution function analysis, PDF, to resolve structure in amorphous metal oxide catalyst films. The analysis is applied here to resolve domain structure differences induced by oxyanion substitution during the electrochemical assembly of amorphous cobalt oxide catalyst films, Co-OEC. PDF patterns for Co-OEC films formed using phosphate, Pi, methylphosphate, MPi, and borate, Bi, electrolyte buffers show that the resulting domains vary in size following the sequence Pi < MPi < Bi. The increases in domain size for CoMPi and CoBi were found to be correlated with increases in the contributions from bilayer and trilayer stacked domains having structures intermediate between those of the LiCoOO and CoO(OH) mineral forms. The lattice structures and offset stacking of adjacent layers in the partially stacked CoMPi and CoBi domains were best matched to those in the LiCoOO layered structure. The results demonstrate the ability of PDF analysis to elucidate features of domain size, structure, defect content and mesoscale organization for amorphous metal oxide catalysts that are not readily accessed by other X-ray techniques. PDF structure analysis is shown to provide a way to characterize domain structures in different forms of amorphous oxide catalysts, and hence provide an opportunity to investigate correlations between domain structure and catalytic activity.
第一行过渡金属的非晶态薄膜析氧催化剂（OECs）有望作为自组装光阳极材料应用于太阳能驱动的光电化学“人工叶片”装置。本报告展示了利用高能X射线散射和原子对分布函数分析（PDF）来解析非晶态金属氧化物催化剂薄膜结构的能力。在此，该分析用于解析非晶态氧化钴催化剂薄膜（Co - OEC）电化学组装过程中氧阴离子取代引起的畴结构差异。使用磷酸盐（Pi）、甲基磷酸盐（MPi）和硼酸盐（Bi）电解质缓冲液形成的Co - OEC薄膜的PDF图谱表明，所得畴的尺寸按Pi < MPi < Bi的顺序变化。发现CoMPi和CoBi的畴尺寸增加与双层和三层堆叠畴的贡献增加相关，这些堆叠畴的结构介于LiCoOO和CoO(OH)矿物形式之间。部分堆叠的CoMPi和CoBi畴中相邻层的晶格结构和错位堆叠与LiCoOO层状结构中的最佳匹配。结果表明，PDF分析能够阐明非晶态金属氧化物催化剂的畴尺寸、结构、缺陷含量和中尺度组织等特征，而这些特征是其他X射线技术难以获得的。PDF结构分析被证明是一种表征不同形式非晶态氧化物催化剂中畴结构的方法，从而为研究畴结构与催化活性之间的相关性提供了机会。
