“…The water oxidation for O 2 evolution can be categorized into three modes: electrocatalytic water oxidation, chemical water oxidation (a chemical oxidant, such as cericammonium nitrate (CAN) and sodium persulfate, is required), and photocatalytic water oxidation (typically a [Ru(bpy) 3 ] 2+ /S 2 O 8 2– /light system with photocatalytic oxidant and photosensitizer). , Chemical water oxidation is the most basic reaction process comparing with artificial photosynthesis, electrocatalytic water oxidation, photocatalytic water oxidation, and so on. In the past, compounds containing noble metals, such as Ru , and Ir , have been reported as high-efficiency chemocatalytic WOCs (CAN as oxidant) and showed noteworthy performances, but the commercial application of these catalysts are restricted due to their expensive prices and scarcity. Hence, many researchers have invested a great deal of attention on the exploration of new, inexpensive and abundantly available materials with good water oxidizing capabilities.…”