Figure 4

(a) CV curves of HQDC-800, HQDC-900, HQDC-1000 and Pt/C catalysts in N₂- or O₂-saturated 0.1 mol L⁻¹ KOH with a scan rate of 50 mV s⁻¹. (b) LSV curves of HQDC-800, HQDC-900, HQDC-1000 and Pt/C electrodes in O₂-saturated 0.1 mol L⁻¹ KOH at −0.4 V with a scan rate of 10 mV s⁻¹ and a rotation rate of 1600 rpm. (c) LSV curves of HQDC-1000 with different rotation rates in O₂-saturated 0.1 mol L⁻¹ KOH at a scan rate of 10 mV s⁻¹. (d) K-L plots of j⁻¹ vs ω^−1/2 at different potential.