Tailoring the Atomic-Local Environment of Carbon Nanotube Tips for Selective H₂O₂ Electrosynthesis at High Current Densities

The atomic-local environment of catalytically active sites plays an important role in tuning the activity of carbon-based metal-free electrocatalysts (C-MFECs). However, the rational regulation of the environment is always impeded by synthetic limitations and insufficient understanding of the formation mechanism of the catalytic sites. Herein, the possible cleavage mechanism of carbon nanotubes (CNTs) through the crossing points during ball-milling is proposed, resulting in abundant CNT tips that are more susceptible to be modified by heteroatoms, achieving precise modulation of the atomic environment at the tips. The obtained CNTs with N,S-rich tips (N,S-TCNTs) exhibit a wide potential window of 0.59 V along with H2O2 selectivity for over 90.0%. Even using air as the O-2 source, the flow cell system with N,S-TCNTs catalyst attains high H2O2 productivity up to 30.37 mol g(cat.)(-1) h(-1)@350 mA cm(-2), superior to most reported C-MFECs. From a practical point of view, a solid electrolyzer based on N,S-TCNTs is further employed to realize the in-situ continuous generation of pure H2O2 solution with high productivity (up to 4.35 mmol cm(-2) h(-1)@300 mA cm(-2); over 300 h). The CNTs with functionalized tips hold great promise for practical applications, even beyond H2O2 generation.