Regulating active hydrogen supply and intermediate binding for pH-universal H2O2 electrosynthesis at ampere-level current density

Electrocatalytic oxygen reduction is an attractive alternative for sustainable H₂O₂ production. However, the electrocatalyst still suffers from low H₂O₂ efficiency due to unsuitable intermediate binding, sluggish active hydrogen (*H) generation in neutral/alkaline solutions and high interfacial proton concentration in acid. Meanwhile, the modulation mechanism remains insufficiently understood. Here we report efficient pH-universal H₂O₂ electrosynthesis at ampere-level current densities by modulating interfacial microenvironment via sulfonic acid (SO₃H)-functionalization of carbon nanotubes (SCNT). Experimental and theoretical results show that SO₃H-functionalization accelerates *H generation from water dissociation for neutral/alkaline H₂O₂ electrosynthesis while creating more alkaline microenvironment in acid. Moreover, it not only optimizes *OOH binding energy and facilitates *OOH generation, but also reduces the energy barrier for *HOOH desorption (rate-determining step). It exhibits good H₂O₂ electrosynthesis performance with Faradaic efficiencies of 81.7-97.2% and H₂O₂ concentrations of 834-1537 mM (0.8 min) at pH 0.7-13 and 1.0-1.5 A cm^-2. The estimated cost for H₂O₂ electrosynthesis is 28.5% of industrial anthraquinone process. The on-site application of SCNT has been demonstrated by efficient pollutant degradation and sterilization.