Graphene oxide (GO) in water was reduced heterogeneously by decamethylferrocene (DMFc) or ferrocene (Fc) in 1,2-dichloroethane (DCE), which could then act as a catalyst for an interfacial oxygen reduction reaction (ORR) and production of hydrogen peroxide (H 2 O 2 ). The reduced graphene oxide (RGO) produced at the liquid/liquid interface was characterized by using electron microscopy, spectroscopy (Raman, infrared, and electron energy loss), and electrochemical techniques.The oxygenated functional groups at the edge/defects of the RGO surface activate O 2 adsorption, forming superoxidelike adducts that can be protonated at the liquid/liquid interface and reduced by DMFc or Fc. This process is facilitated by the higher electrical conductivity of the RGO sheets. The key feature of this catalytic reaction is the in situ partial-reduction of GO at the liquid/liquid interface, forming an efficient and inexpensive catalyst for the production of H 2 O 2 .Electrochemistry at polarized interfaces between two immiscible electrolyte solutions (ITIES) has developed over the past 30 years, in which charge-transfer (electron-and ion-transfer) reactions have found applications in areas such as phase-transfer catalysis, solvent-extraction processes, chemical sensing, solar-energy-conversion systems, drug release and delivery, and in mimicking the function of biological membranes. [1] Liquid/liquid interfaces provide a unique platform at which to study ORRs, at which aqueous protons react with organic solubilized electron donors in the absence or presence of adsorbed catalysts, usually through a proton-coupled electron-transfer (PCET) reaction. [2] The molecular catalysts studied include cobalt, [3] free-base porphyrins, [4] and in situ-deposited platinum particles. [5] The ORR proceeds either by a 4 e À /4 H + pathway to produce water or a 2 e À /2 H + route to yield H 2 O 2 , which is considered a green oxidant.H 2 O 2 is widely used in many industrial areas, particularly in the chemical industry or for environmental protection, and is currently produced on an industrial scale through the biphasic anthrahydroquinone oxidation (AO) process (representing ca. 95 % of the world's H 2 O 2 production). [6] Generally, anthrahydroquinone is oxidized by O 2 to produce H 2 O 2 and anthraquinone and, subsequently, the formed anthraquinone is reduced back to the anthrahydroquinone by using H 2 in the presence of a metal catalyst. Both reactions occur in the organic phase, and H 2 O 2 is recovered by extraction to the aqueous phase. [6] The advantage of the AO process is the very high yield of H 2 O 2 generated per cycle. Conversely, side reactions generating organic byproducts need to be dealt with by regenerating the solution and by using separation techniques to eliminate such impurities. Conceptually, following the AO process, the reduction of O 2 was investigated at quinone-modified carbon surfaces. O 2 reduction to H 2 O 2 was mediated by surface-bound quinone groups via superoxide anion intermediates, [7] and such modified elec...