Supplement Number 1

Experimental Section, Structural, morphological, and compositional characterization, Electrochemical Characterizations, and Electrochemical Calculations. Stepped Potential Electrochemical Impedance Spectroscopy (SPEIS). EDS of W2N and TiN. HRTEM image of W2N. Electrochemical graphs and discussion of TiN TFE. Phase plot of W2N. Areal Ragone plot, and Literature Comparison table of ASC device.