Fig. 2: ORR performance of Pt-X-CNT catalysts cast RRDE in 0.1 M HClO₄.

a Linear sweep voltammetry (LSV) of Pt-N-CNT (blue), Pt-S-CNT (red), Pt-C-CNT (green) and N-CNT reference recorded at 1600 rpm and a scan rate of 5 mV s⁻¹, together with the detected H₂O₂ currents on the ring electrode (upper panel) at a fixed potential of 1.2 V vs. RHE. The catalyst loading was fixed at 0.1 mg cm⁻². b Calculated H₂O₂ selectivity and electron transfer number (n) during LSV scan. H₂O₂ selectivity and n were plotted from the onset potential that reached 0.1 mA cm⁻² H₂O₂ partial current density. c Performance map for the electrocatalytic O₂-to-H₂O₂ conversion in acidic electrolyte, the detailed sample information could be found in Supplementary Table 1.