Photocatalytic H₂O₂ Production over Ultrathin Layered Double Hydroxide with 3.92% Solar-to-H₂O₂ Efficiency

Artificial photosynthesis of hydrogen peroxide (H₂O₂) from earth-abundant water and oxygen is a sustainable approach, however current photocatalysts suffer from low production rate and solar-to-chemical conversion efficiency (< 1.5%). Herein, we report that nickel-chromium layered double hydroxide with intercalated nitrate (NiCrOOH-NO₃) and a thickness of ~ 4.4 nm is an efficient photocatalyst, enabling a H₂O₂ production yield of 28.7 mmol g^-1 h^-1 under visible light irradiation with 3.92% solar-to-chemical conversion efficiency. Experimental and computational studies have revealed an inherent facet-dependent reduction-oxidation reaction behavior and spatial separation of photogenerated electrons and holes. An unexpected role of intercalated nitrate is demonstrated, which promotes excited electron-hole spatial separation and facilitates the electron transfer to oxygen intermediate via delocalization. This work provides understandings in the impact of nanostructure and anion in the design of advanced photocatalysts, paving the way toward practical synthesis of H₂O₂ using fully solar-driven renewable energy.