Dual‐Fractal Design of Hierarchical RuO ₂ /NiO Heterojunction for Efficient Seawater Electrooxidation under Optical Field

Abstract Photo‐assisted electrocatalysis provides an effective approach to remarkably improve the performance of electrocatalytic reactions in seawater. However, the application of this technology requires the catalysts to exhibit high photo‐responsiveness, efficient carrier transfer, and strong resistance to Cl ^– ‐induced corrosion. Moreover, the fundamental mechanisms that drive the performance enhancement in optical fields still need to be further investigated. This study presents a novel design of a dual fractal RuO ₂ /NiO heterojunction with sheet‐like fractal NiO support and branched fractal RuO ₂ load (denoted as RuO ₂ (B)/NiO(S)), possessing the features of enhanced photogenerated carriers, efficient directed carrier transfer, and inhibition of Cl ⁻ ‐induced corrosion. In comparison to its single‐fractal and non‐fractal counterparts, RuO ₂ (B)/NiO(S) exhibits significantly enhanced catalytic activity, superior durability, and morphological and chemical compositional stability during the photo‐assisted oxygen evolution reaction (OER) in seawater. Both experiments and theoretical calculations indicate that the significant improvement in photo‐assisted OER performance of RuO ₂ (B)/NiO(S) results from the synergistic effects associated with dual fractal structures, which include more photogenerated carriers in the sheet‐like fractal NiO support, rapid directed carrier transfer into the branched fractal RuO ₂ load, and its high resistance to Cl ⁻ ‐induced corrosion.