Graphite Paper-based Electrode As Electrocatalyst For Oxygen Evolution Reaction

Graphite paper(GP)is a flexible sheet made by compressing a collection of exfoliated graphite,inherently possesses many advantages,such as low price,rich source,environmentally friendly,resistant to high temperature and high pressure.GP mainly used in manufacturing of thermal conductivity of high temperature sealing element and the micro device components.In addition,it is also a kind of flexible substrate with thermally conductive ability and good chemical stability.In this thesis,graphite paper was used as a substrate for electrode,and the active material was synthesized via simple electrodeposition or hydrothermal method.The performance of electrocatalyst relating to the deposition parameters was discussed.The research content of this paper was summarized below.Firstly,by using manganese acetate and ammonium acetate as the raw materials,the manganese oxide deposit was supported on GP via an electrodeposition method.The morphology,structures and performance of catalyst was characterized by scanning electron microscope(SEM),X-ray powder diffraction(XRD)and electro-catalytic activities toward the OER reaction.The optimization of the sedimentary conditions such as current density,temperature and solution concentration which have an influence on OER performance was gained.The experimental results showed that a 3D network porous structure composed of nanosheets was formed when deposited at the current density of 3 mA cm 2,at 70 ℃ and the concentration of raw materials of 0.02 mol·L-1 Mn(Ac)2 + 0.01 mol L-1 NH4Ac.In view of the structure with good ion transport channel and large specific surface area,it showed high catalytic activity toward OER.Further research showed that the calcination at 350 ℃ can improve the electric catalytic performance with less change in the morphology of electrode.The calcined electrode under neutral condition also showed excellent OER activity.Secondly,an amorphous Ni-Fe hydroxide thin films was supported on GP via an electrodeposition method,using Ni(NO3)2 and Fe(NO3)3 as precursor.The influence of depositional model such as potentiostatic,cyclic voltammetric and potentiostatic pulse techniques toward OER performance was discussed.To gain the optimization of the sedimentary conditions,the working conditions were studied in view of the different depositional model.The morphology,valence state and performance of catalyst was characterized by SEM,XPS and electro-catalytic activities toward the OER experiments.The experimental results show that the porous structure formed by nanoparticles had the optimal performance which deposited at the model of potentiostatic pulse at 50 ℃,in which the ratio of nickel/iron was 9:1.Finally,the manganese oxide film was deposited on GP via a hydrothermal method,by using KMnO4 as oxidant and GP as the reducing agent and substrate.The morphology,structures and performance of catalyst was characterized by SEM,XPS and electro-catalytic activities toward the OER experiments.The influences of hydrothermal temperature and reaction time toward morphology and OER activity were investigated.The experimental results showed that a network structure composed of nanowires and nanoparticles was formed when hydrothermally deposition at 140 ℃ for 6 h.Such structure led to high-speed ion transport,enlarged active surface area and strong adhesion between manganese oxide and support,and thus,the enhanced OER activity of the electrode was achieved.A new substrate was gained after dissolving manganese oxide film.SEM images showed that a porous Channel structure on the surface of GP was formed.Which offered more active sites and led to enhanced OER activity when compare to the original GP.