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.

Realization of stable and industrial-level hydrogen peroxide electroproduction still faces great challenge due large partly to the easy decomposition of this product. Here the authors report a strategy to achieve superior performance by promoting an increased electron density of Co center due to the introduction of sulfur atoms in the linking units of 2D CoPc-S-COF