Intensifying oxygen mass transport with a bioinspired 3D cathode for efficient and hydrogen-free electrochlorination

• Lung-inspired 3D Pt@TiO 2 -Ti cathode achieves hydrogen-free electrochlorination. • Asymmetric hydrophilic/hydrophobic design facilitates O 2 transport. • A high ORR current density of 22.6 mA·cm –2 is achieved. • Marine diatom biofouling is inhibited at a low chlorine dose of 1 mg·L –1 . Marine biofouling presents a persistent and costly challenge to maritime infrastructure, compromising operational efficiency and material integrity. While electrochemical seawater chlorination is an effective antifouling strategy, its widespread application is hindered by inefficient and hazardous hydrogen evolution at the cathode. Herein, we design and fabricate a bioinspired three-dimensional Pt@TiO 2 -Ti electrode that enables hydrogen-free electrochlorination by promoting oxygen reduction reaction (ORR). The electrode was engineered with asymmetric surface wettability by combining hydrophilic and hydrophobic domains with a polypropylene membrane, creating a hollow structure that establishes a stable gas-liquid-solid three-phase interface for efficient oxygen consumption. This unique design achieves a high ORR current density of 22.6 mA·cm –2 at a cell voltage of 2.0 V, which is 4.3 times higher than that of planer electrodes. In-situ mass spectrometry definitively confirms the complete suppression of hydrogen evolution. The system yields an active chlorine concentration of 55.65 mg·L –1 after 60 min electrolysis in natural seawater and demonstrates potent antifouling efficacy, maintaining zero biomass accumulation at a low chlorine dose of 1 mg·L –1 . By decoupling chlorine generation from hydrogen evolution, this work presents a robust strategy for developing safe, energy-efficient, and environmentally sustainable antifouling systems for diverse marine applications.