Maximally exploiting active sites on Yolk@shell nanoreactor: Nearly 100% PMS activation efficiency and outstanding performance over full pH range in Fenton-like reaction

In Fenton-like reaction, peroxymonosulfate (PMS) could be activated by either transition metals or graphitized carbon. These two activation paths had their own advantages and disadvantages. To simultaneously increase the PMS activation efficiency and degradation performance, lower the metal leaching, and improve the environmental adaption; herein, a yolk@shell nanoreactor was designed, where Kirkendall effect induced abundant hollow CoO nanoparticles were encapsulated inside a Co, N atoms co-doped graphitized carbon (Co-N-GC) shell. Because of the full exploitation of active sites on yolk@shell nanoreactor, nearly 100% of PMS activation efficiency was realized and 80.0% of tetracycline (TC) (50 mg/L) was degraded within 40 min. Under the protection of Co-N-GC shell, TC were effectively degraded over the full pH range or in the presence of various inorganic anions, and the leached Co 2+ was only 0.462 mg/L even after 5 cycles. This study provided a new vision to improve the Fenton-like reaction using yolk@shell nanoreactor. In the reaction, PMS firstly adsorbed onto the CoN 4 sites on the Co-N-GC shell surface and then activated to be 1 O 2 . Part of PMS were diffused into the cavity via the porous shell, and activated to be SO 4 •- and • OH on the hollow CoO nanoparticles surface. TC was degraded via both radical path (SO 4 •- and • OH) and non-radical path ( 1 O 2 ), in which 1 O 2 was the primary reactive species, leading to outstanding environmental adaption. • Co, N atoms are co-doped in GC shell, and CoO yolks are hollowed by Kirkendall effect. • PMS activation efficiency is 95.8% by fully exploiting active sites of CoO@Co-N-GC. • On CoN 4 site, PMS donates e - and main species 1 O 2 is formed via SO 5 •- as intermediate. • CoO@Co-N-GC effectively works under full pH values or various anions. • Leached Co 2+ is 0.462 mg/L after 5th run, completely meeting China Emission Standard.