Dithiine-linked metalphthalocyanine framework with undulated layers for highly efficient and stable H2O2 electroproduction

Abstract

Realization of stable and industrial-level H2O2 electroproduction still faces great challenge due large partly to the easy decomposition of H2O2. Herein, a two-dimensional dithiine-linked phthalocyaninato cobalt (CoPc)-based covalent organic framework (COF), CoPc-S-COF, was afforded from the reaction of hexadecafluorophthalocyaninato cobalt (II) with 1,2,4,5-benzenetetrathiol. Introduction of the sulfur atoms with large atomic radius and two lone-pairs of electrons in the C-S-C linking unit leads to an undulated layered structure and an increased electron density of the Co center for CoPc-S-COF according to a series of experiments in combination with theoretical calculations. The former structural effect allows the exposition of more Co sites to enhance the COF catalytic performance, while the latter electronic effect activates the 2e− oxygen reduction reaction (2e− ORR) but deactivates the H2O2 decomposition capability of the same Co center, as a total result enabling CoPc-S-COF to display good electrocatalytic H2O2 production performance with a remarkable H2O2 selectivity of >95% and a stable H2O2 production with a concentration of 0.48 wt% under a high current density of 125 mA cm−2 at an applied potential of ca. 0.67 V versus RHE for 20 h in a flow cell, representing the thus far reported best H2O2 synthesis COFs electrocatalysts.