Multiple active cobalt species embedded in microporous nitrogen-doped carbon network for the selective production of...

To obtain excellent electrocatalysts for improving H₂O₂ yield and selectivity, we formulated a novel method for embedding cobalt catalytic active sites in porous two-dimensional nitrogen-doped carbon network (CN_y) network and employed them as excellent two-electron oxygen reduction reaction (2e^--ORR) electrocatalysts. The polymeric cobalt-based metal-organic framework (polyCo-MOF) and melamine-cyanuric acid-complex (MCA) hybrid (denoted as polyCo-MOF@MCA) was used as a precursor for preparing a series of electrocatalysts comprising multiple active sites such as metallic Co, CoO_x, or Co-N, which are homogeneously embedded in the porous two-dimensional CN_y network through pyrolysis at high temperatures (600 °C, 700 °C, and 800 °C) under N₂ atmosphere. The obtained CoO_x/Co@CN_y,700 hybrid by pyrolyzing polyCo-MOF@MCA at 700 °C displayed remarkably high H₂O₂ production and large selectivity in an alkaline solution. The possible catalytic mechanism of CoO_x/Co@CN_y,700 toward 2e^--ORR was identified by determining the catalytic kinetics and control experiments. The cathode assembled with the CoO_x/Co@CN_y,700 hybrid showed the maximum H₂O₂ production of 405 mmol L^-1g_cat.^-1h^-1 with a high Faradaic efficiency of 88.9 % at 0.65 V. The present work demonstrated a novel strategy for identifying excellent electrocatalysts with homogeneously dispersed multiple active sites and high production and selectivity for H₂O₂ synthesis, extending the applications of porous organic frameworks to the field of clean energy.