The　cooperation　between　metal　single　atom　(SA)　and　atomic　cluster　(AC)　within　an　electrocatalyst　has　showcased　enormous　potential　in　2e(-)　oxygen　reduction　reaction　(ORR)　for　hydrogen　peroxide　(H2O2)　production.　Nevertheless,　developing　an　SA-AC　catalyst　with　the　synergy　of　optimized　functional　groups　to　afford　advanced　catalytic　capability　has　been　challenging.　Herein,　a　new　and　highly　effective　catalyst　with　tandem　cobalt　SA-AC　moieties　and　C　&　horbar;O　&　horbar;C　functional　group　decorations　anchored　over　carbon　nanotubes　is　presented,　which　is　denoted　as　Co　SA-AC(C　&　horbar;O　&　horbar;C).　As　an　electrocatalyst,　Co　SA-AC(C　&　horbar;O　&　horbar;C)　demonstrates　favorable　activity,　selectivity,　and　stability　for　2e(-)　ORR,　delivering　an　onset　potential　of　0.72　V　(vs　RHE)　and　an　H2O2　selectivity　of　97.6%　in　0.5　m　H2SO4.　In　a　flow-cell　reactor,　the　Co　SA-AC(C　&　horbar;O　&　horbar;C)　realizes　an　H2O2　production　rate　of　3.88　mol　g(cat)(-1)　h(-1)　at　300　mA　cm(-2)　targeting　on-site　pollutant　treatment　by　integrating　a　Fenton-like　process.　The　theoretical　computations　guide　the　selection　of　C　&　horbar;O　&　horbar;C　among　the　functional　group　decorations　and　reveal　the　actual　active　sites　to　locate　at　Co　SAs,　while　the　synergistic　effect　of　Co　ACs　and　C　&　horbar;O　&　horbar;C　groups　helps　optimize　the　*OOH　binding　and　modulate　the　electronic　structure.