Abstract
Transition metal oxides have been found great potential to be next generation electrode materials for efficient and low cost energy conversion and storage. Various transition metal oxides with redox ability have been investigated under electrochemical conditions. They have been used as oxygen electrocatalysts for ORR and OER, which are critical reactions for developing renewable energy technologies like fuel cells, metal-air batteries, and water electrolyzers. This presentation will present a systematic study on spinel oxides’ redox ability and oxygen electrocatalysis. [1,2] Starting with a model system of Mn-Co spinel, the presentation will introduce the correlation of oxygen catalytic activities of these oxides and their intrinsic chemical properties. The catalytic activity was measured by rotating disk technique and the intrinsic chemical properties were probed by synchrotron X-ray absorption techniques. It was found that molecular orbital theory is able to well-explain their activities.[3,4] The attention was further extended from cubic Mn-Co spinels to tetragonal Mn-Co spinels and it was found that the molecular theory is again dominant in determining the catalytic activies. This mechanistic principle is further applied to explain the ORR/OER activities of other spinels containing other transition metals (Fe, Ni, Zn, Li, and etc.). 

References
[1] Wei C, Feng Z, Baisariyev M, Yu L, Zeng L, Wu T, Zhao H, Huang Y, Bedzyk M, Sritharan T, Xu Z, Chemistry of Materials, 2016, 28, 4129.
[2] Wei C, Feng Z, Scherer G, Barber J, Shao-Horn Y, Xu Z, submitted.
[3] Suntivich J, Gasteiger, HA, Yabuuchi, N, Nakanishi H, Goodenough, JB, Shao-Horn, Y. Nat. Chem. 3 (2011) 546.
[4] Suntivich J, May KJ, Gasteiger HA, Goodenough JB, Shao-Horn Y, Science 334 (2011) 1383.

Biography Dr. Zhichuan Xu is an assistant professor in the School of Materials Science and Engineering at Nanyang Technological University. Dr. Xu received his PhD training from Lanzhou University, Institute of Physics, CAS, and Brown University (2002-2008). He worked in State University of New York at Binghamton as a research associate (2007-2009) and then he worked in Massachusetts Institute of Technology as a postdoctoral researcher (2009-2012). Dr. Xu's research interests include electrochemistry, catalysis, energy storage, magnetic nanomaterials, and sensors.