Electron Injection From B ₄ C to Sn Sites Optimizes *OOH Adsorption Enabling Efficient H ₂ O ₂ Electrosynthesis

The development of efficient non‐precious metal electrocatalysts is a key challenge for the sustainable electrosynthesis of H 2 O 2 . In this study, a Sn/B 4 C composite catalyst was constructed via low‐temperature pyrolysis under a hydrogen atmosphere. The optimized Sn/B 4 C‐3 exhibited excellent 2e − ORR performance, achieving 93.69% H 2 O 2 selectivity in 0.1 M KOH and 91.9% selectivity in 0.05 M Na 2 SO 4 in RRDE measurements. In a neutral flow cell, the Sn/B 4 C‐3 delivered an H 2 O 2 production rate of 13.33 mol g cat −1 h −1 with a Faradaic efficiency of 91.38%, and maintained operation for 130 h. XPS and in situ ATR‐SEIRAS analyses reveal that electron transfer from B 4 C to Sn generates electron‐rich Sn centers, which optimally modulate the adsorption energy of the key *OOH intermediate. DFT calculations confirm that these centers lower the energy barrier for H 2 O 2 formation and enable optimal *OOH binding, thereby steering the pathway toward selective 2e − ORR. The catalyst maintained stable performance over 130 h of continuous operation in a flow cell. Furthermore, the in situ generated H 2 O 2 solution inactivated Escherichia coli and Streptomyces griseus within 40 min, achieving 99% sterilization efficiency. This study introduces an innovative design principle for electrocatalysts based on metal‐carbide synergy, promoting sustainable H 2 O 2 production for applications such as microbial disinfection.