Heterojunction Engineering of Thiophene–Sulfur Covalent Organic Frameworks via Amino-Functionalized MXene Incorporation for Enhanced H₂O₂ Electrocatalysis

Two-electron oxygen reduction reaction (2e– ORR) offers a promising alternative for hydrogen peroxide (H2O2) production. However, this process necessitates the electrocatalysts with appropriate adsorption energy for the oxygen-containing intermediates, posing a very challenging but meaningful task. Herein, for the first time, we applied the heterojunction engineering strategy to rationally design a specific N-MX@COF-S2 heterojunction via in situ growth of the highly active thiophene-sulfur covalent organic frameworks (COF-S2) on the amino-functionalized MXene (N-MX). N-MX effectively regulates the charge distribution of COF-S2 and thus enables efficient and selective production of H2O2 via 2e– ORR. The results reveal that a special built-in electric field (BIEF) is formed in the heterojunction, the electrons are rearranged and transferred from COF-S2 to N-MX, which strengthens the adsorption of the OOH* and lowers the reaction barrier. As a result, N-MX@COF-S2 achieves the H2O2 selectivity higher than 90% from 0.2 to 0 V vs RHE, and the Faradaic efficiency arrives at 81% at −250 mA cm–2 in neutral media. This study offers a rational regulatory strategy for H2O2 production by heterojunction engineering to promote the development of COF-based electrocatalysts.