Figure 4: Electrocatalytic hydrogen and oxygen evolution of different catalysts.

(a,b) Polarization curves for HER and OER measured at a scan rate of 5 mV s−1 in 1 M KOH electrolyte; (c,d) chronoamperometric responses (i-t) recorded on 2.5H-PHNCMs for 24 h at a constant applied potential of −0.13 V versus RHE for HER and 1.53 V versus RHE for OER; (e,f) the fitting plots showing Cdl for HER and OER.