S1 Supporting information Copper Nitride Nanostructure for the Electrocatalytic Reduction of Oxygen: Kinetics and Reaction Pathway Siniya Mondal and C. Retna Raj * Functional Materials and Electrochemistry Lab, Department of Chemistry Indian Institute of Technology, Kharagpur Kharagpur 721302, India E(mail: crraj@chem.iitkgp.ernet.in