Continuous Electrosynthesis\nof Pure H<sub>2</sub>O<sub>2</sub> Solution with Medical-Grade Concentration\nby a Conductive\nNi-Phthalocyanine-Based Covalent Organic Framework

Electrosynthesis of H<sub>2</sub>O<sub>2</sub> provides\nan environmentally\nfriendly alternative to the traditional anthraquinone method employed\nin industry, but suffers from impurities and restricted yield rate\nand concentration of H<sub>2</sub>O<sub>2</sub>. Herein, we demonstrated\na Ni-phthalocyanine-based covalent-organic framework (COF, denoted\nas <b>BBL-PcNi</b>) with a higher inherent conductivity of 1.14\n× 10<sup>–5</sup> S m<sup>–1</sup>, which exhibited\nan ultrahigh current density of 530 mA cm<sup>–2</sup> with\na Faradaic efficiency (H<sub>2</sub>O<sub>2</sub>) of ∼100%\nat a low cell voltage of 3.5 V. Notably, this high level of performance\nis maintained over a continuous operation of 200 h without noticeable\ndegradation. When integrated into a scale-up membrane electrode assembly\nelectrolyzer and operated at ∼3300 mA at a very low cell voltage\nof 2 V, <b>BBL-PcNi</b> continuously yielded a pure H<sub>2</sub>O<sub>2</sub> solution with medical-grade concentration (3.5 wt %),\nwhich is at least 3.5 times higher than previously reported catalysts\nand 1.5 times the output of the traditional anthraquinone process.\nA mechanistic study revealed that enhancing the π-conjugation\nto reduce the band gap of the molecular catalytic sites integrated\ninto a COF is more effective to enhance its inherent electron transport\nability, thereby significantly improving the electrocatalytic performance\nfor H<sub>2</sub>O<sub>2</sub> generation.