关键词: MnO₂, 还原氧化石墨烯, H₂O₂, 电催化, 水热法

Fuel cells which use hydrogen peroxide as oxidant have been widely studied and presents good development foreground. As a liquid fuel, H₂O₂ possesses advantages of easily storage and transportation which make it can be widely used in underwater and space as a power source. At present, the most widely used catalysts for H₂O₂ electroreduction are noble metal catalysts. Compared with noble metals, transition metal oxides possess advantages of low cost and extensive sources. However, the catalytic activity of transition metal oxides is still much lower than noble metals. Therefore, many efforts should be made to improve the electrochemical performance of transition metal oxides. In this work, rGO is used as an additive to improve the electrochemcial performance of MnO₂. An original electrode of MnO₂ in-situ supported on reduced graphene oxide modified Ni foam (MnO₂/rGO@Ni foam) is prepared through two-step hydrothermal methods. Primarily, the novel current collector of rGO@Ni foam is obtained with larger surface area which is beneficial to the next loading of MnO₂. Secondly, MnO₂ is grown on the rGO@Ni foam also by a hydrothermal treatment. Besides large surface area, the addition of rGO can provide more channels for electron transfer and then accelerate the reaction rate of H₂O₂ reduction. The morphology and phase composition of the as-prepared electrode are investigated by measurements of X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). It can be concluded from SEM and TEM images, both rGO and MnO₂ exhibit sheet-like structure and there are many gaps existing between these sheets. Especially, the as-prepared MnO₂ nanosheets builds a honeycomb structure which makes positive effects on the contact between H₂O₂ and catalyst. And XRD and HRTEM results show that MnO₂ and rGO are successfully prepared on Ni foam. The electrochemical performance of the MnO₂/rGO@Ni foam electrode toward H₂O₂ reduction is investigated by cyclic voltammetry and chronoamperometry in a three-electrode system in solutions of NaOH and H₂O₂. Results reveal that the reduction current density of H₂O₂ reduction on the MnO₂/rGO@Ni foam electrode reaches 240 mA/cm² in a solution of 1.0 mol/L H₂O₂ and 3 mol/L NaOH at -0.8 V which is much higher than that on MnO₂ directly supported on Ni foam (MnO₂@Ni foam). At the same time, a better stability is also achieved on the MnO₂/rGO@Ni foam electrode. Generally speaking, the addition of rGO highly improves the electrocatalytic activity and stability of the as-prepared electrode indicating great application prospect in the future.

Key words: MnO₂, rGO, H₂O₂, electrocatalysis, hydrothermal method