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.