Single-atom catalysts (SACs) are flourishing in various fields because of their 100% atomic utilization. However, their uncontrollable selectivity, poor stability and vulnerable inactivation remain critical challenges. According to theoretical predictions and experiments, a heteronuclear CoZn dual-single-atom confined in N/O-doped hollow carbon nanotube reactors (CoZnSA@CNTs) was synthesized via a spatial confinement growth strategy. CoZnSA@CNTs exhibited superior performance for H2O2 electrosynthesis over the entire pH range due to dual-confinement of the atomic sites and O2 molecule. CoZnSA@CNTs was favorable for H2O2 production mainly because the synergy of adjacent atomic sites, defect-rich feature and nanotube reactor promoted O2 enrichment and enhanced H2O2 reactivity/selectivity. The H2O2 selectivity reached nearly 100% in a range of 0.2 ∼ 0.65V versus RHE and the yield achieved 7.50M gcat -1 with CoZnSA@CNTs/carbon fiber felt, which exceeded most of the reported SACs in H-type cells. The obtained H2O2 was converted directly to sodium percarbonate and sodium perborate in a safe way for H2O2 storage/transportation. The sequential dual-cathode electron-Fenton process promoted the formation of reactive oxygen species (•OH, 1O2 and •O2 -) by activating the in-situ generated H2O2, enabling accelerated degradation of various pollutants and Cr(VI) detoxification in actual wastewater. This work proposes a promising confinement strategy for catalyst design and selectivity regulation of complex reactions. This article is protected by copyright. All rights reserved.