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

Abstract

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 (CNy) 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, CoOx, or Co-N, which are homogeneously embedded in the porous two-dimensional CNy network through pyrolysis at high temperatures (600 °C, 700 °C, and 800 °C) under N2 atmosphere. The obtained CoOx/Co@CNy,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 CoOx/Co@CNy,700 toward 2e−-ORR was identified by determining the catalytic kinetics and control experiments. The cathode assembled with the CoOx/Co@CNy,700 hybrid showed the maximum H2O2 production of 405 mmol L−1gcat.−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.