The　surface/interface　electronic　structure　of　metal　catalysts　plays　a　decisive　role　in　electrocatalytic　reactions.　Direct　monitoring　of　intermediates　during　the　oxygen　reduction　reaction　(ORR)　is　an　accessible　method　to　elucidate　the　interaction　between　intermediates　and　electronic　effects　and　to　correlate　this　interaction　with　ORR　activity.　Herein,　the　reaction　processes　and　intermediates　of　ORR　on　highly　efficient　PtCoSn　ternary　nanoalloys　were　explored　by　surface-enhanced　Raman　spectroscopy　(SERS)　via　a　＂borrowing＂　strategy.　Reactive　*OOH　intermediates　were　captured　under　ORR　conditions　to　reveal　the　critical　role　of　interfacial　electronic　effects　in　ORR　at　a　molecular　level.　Direct　SERS　evidence　demonstrated　that　alloying　with　Co　and　Sn　can　tailor　the　electronic　structure　of　Pt,　thus　changing　the　configuration　of　*OOH　on　the　surface　to　a　weaker　energy　state.　Combined　with　density　functional　theory　(DFT)　calculation　and　X-ray　photoelectron　spectroscopy　(XPS),　it　was　concluded　that　the　electronic　effects　of　the　alloyed　surface　induced　the　*OOH　configuration　to　converge　toward　the　alloy　surface.　Especially　when　Sn　was　doped,　the　more　stable　PtCoSn　structure　enabled　the　*OOH　adsorption　configuration　almost　parallel　to　the　surface,　which　greatly　promoted　the　dissociation　of　the　O-O　bond,　leading　to　the　outstanding　ORR　performance　of　PtCoSn.　These　results　showed　that　in　situ　SERS　investigation　delivered　direct　spectral　evidence　for　the　increase　of　ORR　activity　caused　by　the　electronic　effect,　which　is　expected　to　provide　practical　theoretical　guidance　for　the　construction　of　highly　active　ORR　electrocatalysts　in　the　future.