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

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 & sdot; cm(-2) for 3600 s in our self-made H-type cell, and the cumulative H2O2 production reaches 359.2 mg & sdot; 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.