A study demonstrates that nanocurvature-induced electric fields can be used to control the activity of single-atom electrocatalysts (SACs). By hosting SACs on spherical carbon supports with varying nanocurvature, researchers achieved uniform electric field modulation. In-situ Raman spectroscopy with a Stark shift reporter confirmed that higher nanocurvature leads to stronger electric fields. This strategy was effective across various SAC systems and electrocatalytic reactions. For example, Ni SACs with optimized nanocurvature achieved a high CO partial current density of -400 mA cm⁻² at >99% Faradaic efficiency for CO₂ reduction in acidic media. The study also showed that nanocurvature significantly impacts SAC activity for reactions with intermediates having high dipole moments or polarizability. The results indicate that electric field modulation can be used to control SAC activity and bypass conventional scaling relations. The findings suggest that nanocurvature can be used to control SAC activity and selectivity for a broad range of electrocatalytic reactions. The study also highlights the importance of understanding the role of interfacial electric fields in electrocatalysis. The research provides a new strategy for experimentally evaluating interfacial electric fields under electrochemical conditions. The results demonstrate that nanocurvature can be used to control SAC activity and selectivity for a broad range of electrocatalytic reactions. The study also shows that nanocurvature has no significant influence on acidic HER activity due to the lack of dipole moment and polarizability of the *H intermediate. The findings demonstrate that controllable electric field modulation is a powerful tool for controlling the activity and selectivity of SACs for a broad range of electrocatalytic reactions.A study demonstrates that nanocurvature-induced electric fields can be used to control the activity of single-atom electrocatalysts (SACs). By hosting SACs on spherical carbon supports with varying nanocurvature, researchers achieved uniform electric field modulation. In-situ Raman spectroscopy with a Stark shift reporter confirmed that higher nanocurvature leads to stronger electric fields. This strategy was effective across various SAC systems and electrocatalytic reactions. For example, Ni SACs with optimized nanocurvature achieved a high CO partial current density of -400 mA cm⁻² at >99% Faradaic efficiency for CO₂ reduction in acidic media. The study also showed that nanocurvature significantly impacts SAC activity for reactions with intermediates having high dipole moments or polarizability. The results indicate that electric field modulation can be used to control SAC activity and bypass conventional scaling relations. The findings suggest that nanocurvature can be used to control SAC activity and selectivity for a broad range of electrocatalytic reactions. The study also highlights the importance of understanding the role of interfacial electric fields in electrocatalysis. The research provides a new strategy for experimentally evaluating interfacial electric fields under electrochemical conditions. The results demonstrate that nanocurvature can be used to control SAC activity and selectivity for a broad range of electrocatalytic reactions. The study also shows that nanocurvature has no significant influence on acidic HER activity due to the lack of dipole moment and polarizability of the *H intermediate. The findings demonstrate that controllable electric field modulation is a powerful tool for controlling the activity and selectivity of SACs for a broad range of electrocatalytic reactions.