Efficient Hole Extraction and *OH Alleviation by Pd Nanoparticles on GaN Nanowires in Seawater for Solar‐Driven H2 and H2O2 Generation

Photocatalytic seawater splitting generates green fuel (H2) and value‐added chemicals (H2O2) using earth‐abundant resources. In this study, Pd nanoparticles are integrated with one‐dimensional gallium nitride nanowires (Pd NPs/GaN NWs) on a silicon wafer to produce H2 and H2O2 from seawater powered by sunlight. In‐situ spectroscopic characterizations combined with computational investigations reveal that in this nanohybrid, Pd NPs function as an efficient hole extractor and *OH alleviator during photocatalysis. Meanwhile, the chloride ions in seawater facilitate the H2O→ H2 + H2O2 conversion by improving the charge dynamics and lowering the energy barrier of the key *OH self‐coupling step over Pd sites in the catalytic system. As a result, the photocatalyst delivers an appreciable hydrogen production rate of 2.5 mmol·cm−2·h−1 with a light‐to‐hydrogen (LTH) efficiency of 4.38% in natural seawater under concentrated light irradiation of 3 W·cm‐2 without sacrificial agents and external energies. Notably, water oxidation produces 300 µmol/L [[EQUATION]]H_2O_2H2​O2​ in 2 hours under 3 W/cm² light, using 20 mL water and achieving 0.53% light‐to‐chemical efficiency. The photocatalyst remain stable for 60 hours with turnover number of 1.42 x 107 moles H2 per mole of Pd. The Outdoor tests confirm the potential of solar‐driven seawater splitting for green fuels.