Efficient Electrosynthesis of Hydrogen Peroxide Enabled by a Hierarchical Hollow RE-P-O (RE = Sm, La, Gd) Architecture with Open Channels

The electrochemical two-electron oxygen reduction reaction (2e^- ORR) offers a sustainable pathway for the production of H₂O₂; however, the development of electrocatalysts with exceptional activity, selectivity, and long-term stability remains a challenging task. Herein, a novel approach is presented to addressing this challenge by synthesizing hierarchical hollow SmPO₄ nanospheres with open channels via a two-step hydrothermal treatment. The produced compound demonstrates remarkable 2e^- selectivity, exceeding 93% across a wide potential range of 0.0-0.6 V in 0.1 m KOH, with a peak of 96% at 0.45 V. When employed as the cathode in a flow cell, the synthesized SmPO₄ exhibits impressive stability at 100 mA cm^-2 for 12 h, consistently achieving a Faradaic efficiency above 90%. Using X-ray absorption, in situ Raman and Fourier-transform infrared spectroscopies, theoretical calculations, and post-ORR assessments, it is found that this hollow compound possesses intrinsic open channels and is characterized by the optimal metal atomic spacing, and exceptional structural and compositional stabilities. These factors significantly enhance the thermodynamics, kinetics, and stability of the 2e^- ORR process. Notably, the produced compound also exhibits outstanding 2e^- ORR performance in neutral environments. Furthermore, this strategy can be extended to other hollow rare-earth-P-O compounds, demonstrating excellent 2e^- ORR performance under both neutral and alkaline conditions.