Reduced graphene oxide/Cu^sub 2^O nanostructure composite films as an effective and stable hydrogen evolution photocathode for water splitting

An efficient photocathode consisting of reduced graphene oxide/Cu2O/Cu (rGO/Cu2O/Cu) has been successfully prepared in this work via a facile two step method, consisting of chemical oxidation of a copper foil in alkaline solution using (NH4)2S2O8 as the oxidizing agent, dipping the prepared samples in graphene oxide (GO) solution and calcination at vacuum to form a rGO layer onto Cu2O/Cu photocathode, which acts as a protective layer. The products were composed of a thin Cu2O layer topped with a thin rGO film as the protective coating. The chemical composition and rGO amount in the composite materials were easily controlled by changing the immersion time to enhance PEC performance. UV-Vis spectroscopy, Raman spectroscopy, XRD, SEM, TEM and FTIR spectroscopy were used in the optical and morphological characterization of the graphene oxide and prepared photocathodes. Distinct patches of GO film are formed on the Cu(OH)2 nanostructure surface, as shown by SEM results. Linear sweep voltammetry and chronoamperometry analysis have been applied in the photoelectrochemical characterizations in the dark and under illumination conditions. Photocurrent density provided by rGO/Cu2O/Cu photocathode -2.54 mA cm-2 is three times greater than that of bare Cu2O/Cu photocathode -0.82 mA cm-2 at 0 V vs. RHE under illumination. Low photostability of 42% is exhibited by bare Cu2O/Cu photocathode after 200 s irradiation whereas rGO/Cu2O/Cu photocathode shows approximately 98% of the initial photocurrent density. Therefore, a strategy has been developed in this work for the synthesis of this new photocathode using Cu2O/Cu as an effective photocathode for photoelectrochemical (PEC) water splitting.