Sn Bulk Phase Doping and Surface Modification on Ti₄O₇ for Oxygen Reduction to Hydrogen Peroxide

Abstract

Developing stable and highly selective two‐electron oxygen reduction reaction (2e− ORR) electrocatalysts for producing hydrogen peroxide (H2O2) is considered a major challenge to replace the anthraquinone process and achieve a sustainable green economy. Here, we doped Sn into Ti4O7 (D−Sn−Ti4O7) by simple polymerization post‐calcination method as a high‐efficiency 2e− ORR electrocatalyst. In addition, we also applied plain calcination after the grinding method to load Sn on Ti4O7 (L−Sn−Ti4O7) as a comparison. However, the performance of L−Sn−Ti4O7 is far inferior to that of the D−Sn−Ti4O7. D−Sn−Ti4O7 exhibits a starting potential of 0.769 V (versus the reversible hydrogen electrode, RHE) and a high H2O2 selectivity of 95.7 %. Excitingly, the catalyst can maintain a stable current density of 2.43 mA ⋅ cm−2 for 3600 s in our self‐made H‐type cell, and the cumulative H2O2 production reaches 359.2 mg ⋅ L−1 within 50,000 s at 0.3 V. The performance of D−Sn−Ti4O7 is better than that of the non‐noble metal 2e− ORR catalysts reported so far. The doping of Sn not only improves the conductivity but also leads to the lattice distortion of Ti4O7, further forming more oxygen vacancies and Ti3+, which greatly improves its 2e− ORR performance compared with the original Ti4O7. In contrast, since the Sn on the surface of L−Sn−Ti4O7 displays a synergistic effect with Tin+ (3≤n≤4) of Ti4O7, the active center Tin+ dissociates the O=O bond, making it more inclined to 4e− ORR.