Deliberate Construction of IrO ₂ –PdO Heterointerfaces via Sequential Photodeposition for Selective and Durable Chloride Oxidation

Selective chloride oxidation is the bottleneck in realistic seawater splitting, where oxidation-driven acidification imposes a selectivity–stability trade-off. We report a programmable sequential photodeposition strategy that constructs surface-defined IrO 2 –PdO heterointerfaces on single-crystalline Co 3 O 4 nanocubes, yielding ∼1 nm clusters with controlled composition. This approach enables systematic interface engineering, generating heterointerfaces that stabilize catalyst under acidifying seawater electrolysis. The resulting IrO 2 –PdO/Co 3 O 4 catalyst exhibits nearly 100% selectivity for chloride oxidation over oxygen evolution in neutral NaCl and retains high activity and durability under localized acidification, outperforming IrO 2 /Co 3 O 4, PdO/Co 3 O 4, and commercial Ti/IrRu anodes. Density functional theory calculations show that interfacial electronic interactions optimize Cl* binding and lower activation barriers relative to isolated IrO 2 and PdO. Under continuous-flow conditions, the catalyst offers exceptional durability and sustained HOCl production, demonstrating practical relevance for on-site disinfectant generation. This consecutive photodeposition provides a controllable route to design durable heterointerfaces relevant to seawater electrolysis.