Supplementary Information Tuning the electrocatalytic activity of Co 3 O 4 through discrete elemental doping Jayashree Swaminathan 1, 2 , Anand B. Puthirath 1 , Mihir Ranjan Sahoo 3 , Saroj Kumar Nayak 3* Gelu Costin 4 , Robert Vajtai 1 , Tiva Sharifi 1, 5* , Pulickel M. Ajayan 1 * 1 Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005, USA 2 CSIR- Central Electrochemical Research Institute, Karaikudi, Tamilnadu, India 3 School of Basic Sciences, Indian Institute of Technology Bhubaneswar, India 4 Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, Texas 77005, USA 5 Department of Physics, Umeå University, Umeå, 90187, Sweden Email: ajayan@rice.edu, tiva.sharifi@umu.se, nayaks@iitbbs.ac.in