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Ag 2 O modified CuO nanosheets (Ag 2 O/CuO) serve as both visible-light-driven water oxidation catalysts and visible light absorption centers. [Display omitted] • Ag 2 O/CuO nanosheets provides light-absorption centers in persulfate/NaOH system. • Ag 2 O/CuO catalyst has excellent water oxidation performance in a photosensitizer free system. • Ag 2 O/CuO nanosheets reduced the recombination of electron-hole pairs. • Mechanism of Ag 2 O/CuO nanosheets for water oxidation reaction was proposed. Semiconductors have been given immense attention for years regarding the use of photocatalytic water oxidation reaction (WOR) to reduce the potential barrier. However, some known semiconductors, such as TiO 2 and CuO, exhibit outstanding water oxidation activity in the UV light region. Therefore, it is important to explore the methods to expand the usage of these catalysts in the visible as well as IR regions. This study introduces a simple and facile chemical co-precipitation method to fabricate a sort of Ag 2 O-modified CuO nanosheets with excellent catalytic properties. The as-prepared Ag 2 O/CuO nanosheets exhibit a robust catalytic efficiency towards the visible-light-driven WOR. Due to the addition of Ag 2 O, the Ag 2 O/CuO nanosheets display photocatalytic activity. The total turnover number (TON) was 8.20 and when the effect of chemocatalytic activities was deducted, the TON, quantum yield (QY), and corresponding photonic efficiency (ζp) are 2.92, 0.65 %, and 0.33 %, respectively, which shows that Ag 2 O/CuO nanosheets possess water oxidation sites as well as light-absorption centers. With the synergy effect between the Ag 2 O and CuO, the catalyst efficiently reduced the recombination probability of photoexcited electrons and holes. Intriguingly, Ag 2 O/CuO nanosheets expanded the utility in the visible region as long as 765 nm, which evolved 95.89 % oxygen compared to that of the light cutting off at 420 nm. The insight into the WOR pathway is that surficial –OH groups of Ag 2 O/CuO nanosheets play a key role in this catalytic reaction. The mechanism of Ag 2 O/CuO nanosheets in the persulfate/NaOH system for water oxidation was consequently proposed according to electron spin resonance measurements and two radical scavengers (methanol and tert-butanol alcohol). This study offers useful guidance for developing difunctional water oxidation catalysts without photosensitizers. [ABSTRACT FROM AUTHOR]