Visible light irradiation of an O 2 -saturated acetonitrile (MeCN) solution containing 9-mesityl-10-methylacridinium ion (Acr + –Mes) and MeCN-extracted coal tar results in formation of hydrogen peroxide (H 2 O 2 ). Anthracene and other aromatic hydrocarbons contained in coal tar act as hydrogen sources in the photocatalytic reduction of O 2 to produce H 2 O 2 . The photocatalytic formation of H 2 O 2 is initiated by photoexcitation of Acr + –Mes, which results in formation of the electron-transfer state: Acr–Mes + , followed by electron-transfer from coal tar to the Mes + moiety and electron-transfer from the Acr moiety to O 2 .