The influence of mesopore size distributions on the electrochemical activity and two-electron selectivity of the oxygen reduction reaction in nitrogen-doped and CoOx-loaded activated carbon

The electro-synthesis of hydrogen peroxide (H 2 O 2 ) through the two-electron oxygen reduction reaction (ORR) is an inexpensive and environmentally friendly process. In this study, as catalysts for the ORR, two kinds of activated carbon (AC) with different mesopore size distributions are modified by nitrogen (N)-doping and cobalt oxide (CoO x )-loading treatment. It can be concluded that pyridinic-N and pyrrolic-N (48.94%) are more easily formed on the AC with narrow mesopore size distributions (AC-1, 2–5   nm), however, graphite-N (63.9%) are more easily formed on the AC with broad mesopore size distributions (AC-2, 5–15   nm). Furthermore, Co 3 O 4 and CoO is the predominant crystal loaded onto the modified AC-1 and modified AC-2, respectively. The modified AC-1 has an extremely high propensity for a four-electron ORR pathway, while the modified AC-2 has an extremely high propensity for a two-electron ORR pathway. In addition, a rolling activated carbon electrode (RACE) with low-cost and high-efficiency is fabricated by modified AC-2. The H 2 O 2 electro-synthesis rate and current efficiency for the RACE are 0.236   ±   0.025   mg/h/mA/cm 2 and 63.25   ±   6.79%, respectively.