Synergistic Effect of Bio-Inspired Microenvironment Modulation and Catalytic Site Design Enhances the Oxygen Evolution Performance of Copper-Phenanthroline Catalysts

Abstract

Copper complexes inspired by O₂-activating enzymes have been widely investigated as molecular water oxidation catalysts, capable of facile and reversible O─O bond formation and cleavage under mild conditions. In this study, two copper phenanthroline complexes, namely, Cu(phen) and Cu(dophen), exhibit high turnover frequencies (TOFs) of 74 ± 13 and (5.66 ± 0.29) × 10³ s⁻¹ for water oxidation, respectively. Moreover, amino acid-functionalized carbon dots (CDs) were used to support the adhesion of the [Cu] complexes onto the electrode, significantly enhancing the TOFs of (2.80 ± 0.12) × 10³ and (4.11 ± 0.24) × 10⁴ s⁻¹, respectively, exceeding the activity of photosystem II in nature. Remarkably, the amino acid-functionalized CDs provide a secondary sphere that mimics the catalytic microenvironment of the copper centre, which promotes proton-coupled electron transfer and O─O bond formation. Finally, the photovoltaic-electrolysis (PVE) system was established using CDs-supported Cu catalysts and commercial silicon solar panels, achieving a high solar-to-hydrogen efficiency of 11.59% under the illumination of AM 1.5 G. This represents the most efficient solar-driven water splitting system based on copper-based catalysts to date, introducing the biomimetic secondary sphere to a “proton-rocking” process for water oxidation catalysis and application of the PVE system.