Solar-Driven Water Splitting in Photovoltaic Electrolysis Systems Using Copper Terpyridine Complexes as Oxygen Evolution Catalysts

Copper complexes, as kinds of molecular catalysts bioinspired from the copper O-2-activating enzymes, are attractive targets for water oxidation, which can undergo facile and reversible O-O bond formation and cleavage under mild conditions. Herein, three copper(II) complexes of Cu(tpy), Cu(ctpy), and Cu(pctpy) are investigated as oxygen evolution catalysts, which are designed and synthesized using alpha,alpha ',alpha ''-terpyridyl(tpy) derivatives as ligands. In the electrochemical measurements, the carboxylic-functionalized catalysts of Cu(ctpy) and Cu(pctpy) exhibit high water oxidation turnover frequencies of 1027 and 3363 s(-1), respectively. The astonishing rates of O-2 production exceed the oxygen evolution complex in natural photosystem II. Moreover, the photovoltaic electrolysis (PVE) system is constructed by connecting Si solar panels with the copper complex-decorated electrodes. Under the irradiation of AM1.5G-simulated sunlight, a high photocurrent density of 5.47 mA cm(-2) and solar-to-hydrogen efficiency of 6.81% are achieved for solar water splitting without external bias. This is the first report PVE system using copper complex as a oxygen evolution catalyst molecular catalyst, which is of great significance to simulate the catalytic water oxidation process of natural enzymes and build an artificial photosynthesis system to achieve green, efficient, and stable decomposition of aquatic oxygen.

Automated summary

Three copper complexes were studied as oxygen evolution catalysts, and two of them exhibited high water oxidation activity. In a photovoltaic electrolysis system, the copper complexes achieved efficient solar water splitting for hydrogen production. This work is significant for simulating the catalytic water oxidation process of natural enzymes and developing artificial photosynthesis systems.