Abstract The exploration of a noble-metal-free and nitrogen-doped carbon (M–N/C) composite electrocatalyst for the oxygen reduction reaction (ORR) remains a great challenge. The activities of the M–N/C composite electrocatalysts are mainly affected by the metal active sites. pyridinic nitrogen. and graphitic nitrogen. https://www.ealisboa.com/great-pick-BERKLEY-POWER-WORM-7-100-PACK-super-buy/