1 Electronic Supplementary Information (ESI) Electronic Structure Reconfiguration towards Pyrite NiS 2 via Engineered Heteroatom Defect Boosting Overall Water Splitting Hengjie Liu, † Qun He, † Hongliang Jiang,* ,† Yunxiang Lin, † Youkui Zhang, †,‡ Muhammad Habib, † Shuangming Chen, † and Li Song* ,† † National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience, University of Science and Technology of China, Hefei, Anhui 230029, China. *E-mail: jhlworld@ustc.edu.cn, song2012@ustc.edu.cn. ‡ School of National Defense Science & Technology, Southwest University of Science and Technology, Mianyang 621010, China.