<p>The rational design of catalysts for photocatalytic H₂O₂ production remains a major challenge, as most photocatalysts for H₂O₂ production also tend to decompose H₂O₂. Here, density functional theory (DFT) calculations reveal that amorphous Al₂O₃ clusters anchored on crystalline carbon nitride (CCN) provide efficient oxygen adsorption sites, facilitate electron transfer, and stabilize key *OOH intermediates. Guided by these insights, CCN composites loaded with Al₂O₃ clusters (CCN-Al-x) were synthesized. Experimental studies confirm that the introduction of Al₂O₃ clusters enhances charge separation, suppresses H₂O₂ decomposition and improves the selectivity of the 2e⁻ oxygen reduction reaction (ORR). The optimized CCN-Al-2 achieves an H₂O₂ production rate of 50.2&#xa0;mmol&#xa0;g⁻¹&#xa0;h⁻¹, with an apparent quantum yield (AQY) of 21.6% under 420&#xa0;nm irradiation. This work highlights the critical impact of Al₂O₃ clusters modification on CCN, providing new opportunities for efficient and selective photocatalytic H₂O₂ production.</p> Graphical abstract <p></p>