Efficient electrochemical hydrogen peroxide generation using TiO2/rGO catalyst and its application in electro-Fenton degradation of methyl orange

It is very important to develop efficient and noble-metal-free catalysts for oxygen reduction reaction (ORR) to satisfy the commercial demand of H2O2. Herein, a reduced graphene oxidation (rGO) supported TiO2 nanoparticles (TiO2/rGO) composite was synthesized for ORR by a sol-gel process followed by hydrothermal reduction. The SEM, TEM, XRD, Raman and XPS were used to characterize the TiO2/rGO and the results showed that TiO2 particles were uniformly embedded in the three-dimensional structure of rGO. The ORR process on TiO2/rGO was dominated by two-electron transfer, indicating the generation of hydrogen peroxide. The optimized TiO2/rGO catalyst exhibited excellent catalytic activity towards H2O2 electro-generation in acid solution with a H2O2 accumulated concentration of 41.69 mg/L and current efficiency of 8.21 % after 120 min of electrolysis. The activity of TiO2/rGO was also investigated as electro-Fenton catalyst for the degradation of methyl orange (MO). The MO and COD removal efficiencies at TiO2/rGO cathode reached 98.40 % and 85.14 %, respectively after 120 min of electrolysis. Free radical capture and quenching experiments showed the •OH played a vital role for the MO degradation in electro-Fenton process. Furthermore, the possible degradation pathway of MO was proposed by analyzing the intermediates. This work demonstrated that the prepared TiO2/rGO is a promising catalyst for H2O2 electro-generation.