Atomic Confinement Empowered CoZn Dual-Single-Atom Nanotubes for H₂O₂ Production in Sequential Dual-Cathode Electro-Fenton Process.

Abstract

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 (CoZn_SA@CNTs) is synthesized via spatial confinement growth. CoZn_SA@CNTs exhibit superior performance for H₂O₂ electrosynthesis over the entire pH range due to dual-confinement of atomic sites and O₂ molecule. CoZn_SA@CNTs is 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 reaches ∼100% in a range of 0.2-0.65 V versus RHE and the yield achieves 7.50 M g_cat ^-1 with CoZn_SA@CNTs/carbon fiber felt, exceeding most of the reported SACs in H-type cells. The obtained H₂O₂ is converted directly to sodium percarbonate and sodium perborate in a safe way for H₂O₂ storage/transportation. The sequential dual-cathode electron-Fenton process promotes the formation of reactive oxygen species (•OH, ¹O₂ and •O₂ ^-) by activating the 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.