Fig. 10. Bulk H₂O₂ electrosynthesis stability of Ni–N/C_3_H₂O catalyst tested in an H-type electrochemical cell at a constant potential of 0.6 V for 9 d: (a) Fresh Ni–N/C_3_H₂O-coated electrode for 1 d, (b) after replenishing both electrolytes, the one-day-tested Ni–N/C_3_H₂O-coated electrode for 7 d without exchanging the cathodic electrolyte while replenishing the anodic electrolyte every day, and (c) after replenishing both electrolytes, the eight-day-tested Ni–N/C_3_H₂O-coated electrode for 1 d.