Hydrogen Peroxide Electrosynthesis Under Weak Thermodynamic Driving Conditions Enabled by In Situ Spin-State Tailoring

Two-electron oxygen reduction reaction (2e⁻ ORR) offers a sustainable approach to traditional hydrogen peroxide (H₂O₂) production, and can be scaled up in production capacity and efficiency through integrated energy conversion devices. Achieving the electrosynthesis of H₂O₂ at low electrolytic cell voltages not only reduces energy consumption but also improves economic efficiency. Herein, we engineered the Ga sites as potential-dependent spin-state promoters at interatomic distances into highly active single-atom Co sites. In this system, electron-rich Ga atoms donate extra anti-bonding orbital electrons to Co to induce an in situ transition of Co from a medium-spin (0.70 V) to a low-spin configuration (0.20 V), thereby facilitating smoother intermediates release. In parallel, Ga improves local hydrophilicity and surface polarity toward accelerated proton transfer. Impressively, the catalyst retains >90% H₂O₂ selectivity even if the reaction enters the low-voltage stage and enables a production rate of 13.7 mol g_cat⁻¹ h⁻¹ in a flow cell.