Fig. 7. Chronoamperometry measurements of 1|NiO (a) and 2|NiO (b) immersed in pH 3 buffer containing 0.1 M potassium hydrogen phthalate. E_appl = –0.2 V, –0.4 V and –0.6 V vs. Ag/AgCl (3.0 M NaCl). Chopped light illumination was applied with 30 s intervals (10 cycles of dark current/photocurrent).