Atomic Confinement Empowered CoZn Dual-Single-Atom Nanotubes for H 2 O 2 Production in Sequential Dual-Cathode Electro-Fenton Process.

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 H 2 O 2 electrosynthesis over the entire pH range due to dual-confinement of atomic sites and O 2 molecule. CoZn SA @CNTs is favorable for H 2 O 2 production mainly because the synergy of adjacent atomic sites, defect-rich feature and nanotube reactor promoted O 2 enrichment and enhanced H 2 O 2 reactivity/selectivity. The H 2 O 2 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 H 2 O 2 is converted directly to sodium percarbonate and sodium perborate in a safe way for H 2 O 2 storage/transportation. The sequential dual-cathode electron-Fenton process promotes the formation of reactive oxygen species (•OH, 1 O 2 and •O 2 - ) by activating the generated H 2 O 2 , 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.