Solar Light‐Responsive M x O y /OCN Heterojunction Photocatalysts for Green and Sustainable H ₂ O ₂ Detection and Production

Hydrogen peroxide (H 2 O 2 ), a sustainable and powerful oxidizing agent as well as an energy carrier, has received widespread acclaim in the field of photocatalysis. The production of H 2 O 2 through artificial photosynthesis using water (H 2 O) and oxygen as raw materials, solar energy as the power source, and semiconductor catalysts is regarded as a highly promising technology. Notable developments have occurred in recent years in the photocatalytic synthesis of H 2 O 2 . Recently, the sustainable production of H 2 O 2 from water and oxygen using photochemically active metal oxides with graphitic carbon nitride heterojunction photocatalysts has attracted considerable attention. However, comprehensive studies emphasizing the role of metal oxides with oxygen‐doped carbon nitride heterojunction (M x O y /OCN) photocatalysts, including their influence on photocatalytic performance, generation of oxidative species (e.g., O 2 − , •OH), and efficient activation of ethanol (EtOH) for H 2 O 2 production, remain limited. In this context, we demonstrate that versatile and compatible metal oxides, M x O y (M = Fe, Ti, Ru, Ce, Mn, Mg), integrated with oxygen‐doped carbon nitride (OCN) form heterojunction photocatalysts that significantly enhance H 2 O 2 production. Among them, Fe 2 O 3 /OCN exhibits outstanding activity, along with high TON and TOF. H 2 O 2 was measured using a self‐prepared starch solution, offering a green and simple detection method.