Fig. 5

Electrochemical performance of IrHNC. a Polarization curves IrHNC, Pt/C, and IrNP in nitrogen saturated 0.5 M aq. H2SO4 solution. b Overpotentials of IrHNC, Pt/C and IrNP at current densities of 10 and 100 mA cm−2. c Electrochemical impedance spectroscopy (EIS) curves of IrHNC, Pt/C and IrNP at an overpotential of 10 mV. d Mass activities of IrHNC, Pt/C, and IrNP at overpotentials of 10 and 30 mV. e The TOF values of IrHNC and other recently reported HER electrocatalysts in acidic media. Scan rate: 5 mV s−1