This study investigates the operando formation of highly efficient electrocatalysts induced by heteroatom leaching. The research reveals that the stability of nonmetal dopants in electrocatalysts is often overlooked, and their performance under working conditions may not be directly attributed to the dopants themselves but rather to defective sites formed after leaching. Using fluorinated bismuth oxide (Bi₂O₃-F) as an example, the study shows that the observed high activity and stability in CO₂ reduction reaction (CO₂RR) are not from F-based active sites but from defective Bi sites formed after F leaching. This finding is supported by density functional theory (DFT) calculations and experimental data from various heteroatom-doped nanocatalysts for CO₂RR, HER, ORR, and OER. The study also demonstrates that the leaching of heteroatoms is potential-dependent, with different behaviors observed in various electrochemical processes. For instance, F and N dopants are stable in the ORR potential window but leach at too high or too low potentials. The results suggest that the real role of heteroatoms in electrocatalysis is not always as previously thought, and the formation of active sites in situ after leaching is crucial for understanding catalytic performance. The study provides insights into the real role of heteroatoms and offers a protocol for engineering highly efficient active sites through the leaching process.This study investigates the operando formation of highly efficient electrocatalysts induced by heteroatom leaching. The research reveals that the stability of nonmetal dopants in electrocatalysts is often overlooked, and their performance under working conditions may not be directly attributed to the dopants themselves but rather to defective sites formed after leaching. Using fluorinated bismuth oxide (Bi₂O₃-F) as an example, the study shows that the observed high activity and stability in CO₂ reduction reaction (CO₂RR) are not from F-based active sites but from defective Bi sites formed after F leaching. This finding is supported by density functional theory (DFT) calculations and experimental data from various heteroatom-doped nanocatalysts for CO₂RR, HER, ORR, and OER. The study also demonstrates that the leaching of heteroatoms is potential-dependent, with different behaviors observed in various electrochemical processes. For instance, F and N dopants are stable in the ORR potential window but leach at too high or too low potentials. The results suggest that the real role of heteroatoms in electrocatalysis is not always as previously thought, and the formation of active sites in situ after leaching is crucial for understanding catalytic performance. The study provides insights into the real role of heteroatoms and offers a protocol for engineering highly efficient active sites through the leaching process.