Tang, C.Chen, L.Li, H.Li, L.Jiao, Y.Zheng, Y.Xu, H.Davey, K.Qiao, S.2021-07-212021-07-212021Journal of the American Chemical Society, 2021; 43(20):4819-48270002-78631520-5126http://hdl.handle.net/2440/131257Product selectivity in multielectron electrocatalytic reactions is crucial to energy conversion efficiency and chemical production. However, a present practical drawback is the limited understanding of actual catalytic active sites. Here, using as a prototype single-atom catalysts (SACs) in acidic oxygen reduction reaction (ORR), we report the structure–property relationship of catalysts and show for the first time that molecular-level local structure, including first and second coordination spheres (CSs), rather than individual active atoms, synergistically determines the electrocatalytic response. ORR selectivity on Co-SACs can be tailored from a four-electron to a two-electron pathway by modifying first (N or/and O coordination) and second (C–O–C groups) CSs. Using combined theoretical predictions and experiments, including X-ray absorption fine structure analyses and in situ infrared spectroscopy, we confirm that the unique selectivity change originates from the structure-dependent shift of active sites from the center Co atom to the O-adjacent C atom. We show this optimizes the electronic structure and *OOH adsorption behavior on active sites to give the present “best” activity and selectivity of >95% for acidic H₂O₂ electrosynthesis.en© 2021 American Chemical Societyoxygen reductionenergy conversionchemical productionJournal article100004068810.1021/jacs.1c031350006572128000272-s2.0-85106392680574692Tang, C. [0000-0002-5167-1192]Chen, L. [0000-0002-8898-5769]Li, L. [0000-0002-3301-9029]Jiao, Y. [0000-0003-1329-4290]Zheng, Y. [0000-0002-2411-8041]Xu, H. [0000-0002-9126-1593]Davey, K. [0000-0002-7623-9320]Qiao, S. [0000-0002-1220-1761] [0000-0002-4568-8422]