Hydrothermally Grown Halogen-Doped ZnO Nanorods for\nPhotoelectrochemical Water Oxidation: Experimental and DFT Insights

This study demonstrates the photoelectrochemical\n(PEC) aspects\nof hydrothermally grown halogen-doped ZnO nanorods, analyzing their\nstructural, morphological, optical, and electrical properties under\nvisible light illumination. We find that halogen doping in the ZnO\nmatrix significantly enhances the PEC water splitting performance.\nAmong the four halogen atoms (Cl, Br, F, and I), Cl yields the highest\nphotocurrent density of 0.75 mA/cm<sup>2</sup> at 1.5 V vs Ag/AgCl,\nnearly 5 times that of pristine ZnO nanorods (0.16 mA/cm<sup>2</sup>). This improvement in PEC activity is attributed to the increased\nlight absorption, higher charge carrier density, and efficient separation\nof the photoexcited electron–hole pairs. Cl doping in ZnO increases\nthe free electron concentration and tends to substitute oxygen vacancies,\nthereby reducing the recombination of photogenerated electron–hole\npairs. In addition, the density functional theory calculations provide\ntheoretical insights into the effect of halogen doping on the photocatalytic\nactivity of ZnO. These findings pave the way for the design of efficient\nand cost-effective photoanode materials for PEC applications.