Ultrafine Co nanoparticles confined in nitrogen-doped carbon toward two-electron oxygen reduction reaction for H_(2)O_(2) electrosynthesis in acidic media

Electrocatalytic production of hydrogen peroxide(H_(2)O_(2))by two-electron oxygen reduction reaction(2e^(-)ORR)under acidic condition has been considered to have great application value.Co nanoparticles(CoNPs)coupled with N-doped carbon are a class of potential electrocatalysts.The effective strategies to further enhance their performances are to improve the active sites and stability.Herein,the material containing ultrafine CoNPs confined in a nitrogen-doped carbon matrix(NC@CoNPs)was synthesized by pyrolyzing corresponding precursors,which was obtained through regulating the topological structure of ZIF-67/ZIF-8 with dopamine(DA).The DA self-polymerization process induced the formation of CoNPs with smaller sizes and formed polydopamine film decreased the detachment of CoNPs from the catalyst.High density of Co-N_(x) active sites and defective sites could be identified on NC@CoNPs,leading to high activity and H_(2)O_(2) selectivity,with an onset potential of 0.57 V(vs.RHE)and∼90%selectivity in a wide potential range.An on-site electrochemical removal of organic pollutant was achieved rapidly through an electro-Fenton process,demonstrating its great promise for on-site water treatment application.