Hybrids Y ₂ SiO ₅ :Pr ³⁺ , Nd ³⁺ /g-C ₃ N ₄ Efficiently Generated H ₂ O ₂ in Achieving Conversion from Visible to Ultraviolet Light

To enhance the spectral utilization range for synthesizing H2O2, up-conversion (UC) materials Y2SiO5: Pr3+, Nd3+ (PNY), and g-C3N4 (CN) were successfully combined through a simple thermal treatment method. The evaluation experiment indicates that the optimal ratio of PNY to CN for the composite is 5%. When the catalyst dosage was 1 mg and the ethanol (EtOH) volume was 10 mL, the production rate of H2O2 was the highest, reaching 57.18 mmol·g–1·h–1. The reaction pathway for synthesizing H2O2 is attributed to the oxygen reduction reaction (ORR) rather than the water oxidation reaction (WOR). Under 635 nm wavelength excitation, 5%-PNY/CN composites showed emission peaks at 275, 280, 347, and 492 nm, corresponding to 4f5d→3H4,5,6, 4f5d→3F2,3, 4f5d→3F3,4, and 3P0→3H4 transitions of activator Pr3+, respectively. This confirms the successful conversion of visible (vis)–ultraviolet (UV) light, and the up-conversion quantum yield (UCQY) of 5%-PNY/CN reaches 3.07%. Correspondingly, the production of H2O2 under vis light reached the level of UV light, indicating that the conversion from vis to UV light is effective in increasing the production of H2O2. Finally, a possible photocatalytic cooperative UC photoreaction mechanism was proposed. This presents a novel strategy for the design of innovative photocatalysts.