Revealing promotion of interfacial Pt–O–Fe oxygen bridge structure in PtFe/graphene synthesized by a four-electrode electrochemical system on water splitting

To promote kinetic rate of half reactions in water splitting, we synthesized a bifunctional PtFe/graphene with dual active sites by a facile self-designed four-electrode electrochemical method. Characterization data indicate interfacial oxygen bridge structure of Pt–O–Fe is expectedly formed and electrons transfer from Fe to Pt via this bridge structure. This unique interfacial structure not only regulates electronic structure of Pt and Fe, but also offers interfacial electron-transfer channel to improve overall conductivity, which essentially enhances intrinsic activity towards acidic HER and alkaline OER. For HER, the best Pt–Fe/G shows the mass activity of 4239.3 mA mg−1 at −0.063 V, 3.79 times higher than that of Pt/G (1118.5 mA mg−1) and 5.02 times higher than that of commercial Pt/C (843.1 mA mg−1) catalyst, respectively. Introduction of Fe to Pt decreases the energy barrier of HER process (ΔG∗), and results in conversion of rate-limiting step from H+ adsorption (Volmer step) to H∗ desorption (Tafel step). For OER, the greatest PtFe/G exhibits an overpotential of lower 26 mV (10 mA cm-2) than commercial RuO2 and its mass activity is 16.7 times higher than Fe/G. The formed Pt–O–Fe bond effectively elevates the electrophilic properties and facilitates adsorption of OH−, contributing to the change of rate-limiting step and enormous decrease of reaction activation energy (Ea). This work inspires researchers to construct efficient interfacial oxygen bridge structure to enhance electrocatalytic performance for water splitting and design novel electrochemical method for synthesis of graphene-based composites.