Controllable Preparation Of Metal Oxide Via Plasma And Their Activities For The Oxygen Reduction Reaction

Oxygen reduction reaction?ORR?is an important electrode reaction for many energy conversion devices,such as metal air batteries and fuel cells.The kinetic rate of ORR is very slow,and catalyst is usually used to promote the reaction.At present,the noble metal Pt-based catalyst is considered to be the best catalyst for the ORR in fuel cells.However,the Pt is scare with high price and poor stability,thus the high cost of Pt-based catalyst greatly restricts the commercialization of fuel cells.Therefore,the alternative catalysts with low cost and high activity have attracted wide attention.Among them,transition metal oxides have become the most concerned non-noble metal catalysts for ORR,due to many advantages of low cost,favorable activity and stability,rich resources and environmentally friendly.In this paper,manganese oxide and cobalt oxide were prepared using dielectric barrier discharge?DBD?plasma,This paper made comprehensive characterization of catalysts prepared by plasma and calcination method,then analyzed the advantages of metal oxides obtained by DBD plasma in valence,particle size,dispersion,oxygen adsorption and catalytic activity.The carbon supported potassium permanganate precursor was decomposed into MnO_X@C-D and MnO_X@C-C catalysts by DBD plasma and calcination method,respectively.The MnO_X@C-D contains Mn₃O₄ and MnO phase,its Mn₃O₄ on the surface of catalyst mainly exists in the form of MnO₂?2MnO,and it shows excellent performance in oxygen adsorption.MnO_X@C-C only has Mn₃O₄ phase,its Mn₃O₄ on the surface of catalyst mainly exists in the form of Mn₂O₃?MnO,and the particles severely agglomerate with low oxygen adsorption properties.MnO_X@C-D catalyst shows higher oxygen reduction activity than that of MnO_X@C-C.In addition,we also speculated the decomposition process of potassium permanganate in DBD plasma.The high-energy electrons are main species in DBD plasma.When interacting with KMnO₄,the high-energy electrons of DBD transfer their energy to KMnO₄,leading to the decomposition of KMnO₄.The products from the decomposition of KMnO₄continue to be bombarded by high-energy electrons and be further decomposed.The precursor,cobalt oxide supported on reduced graphene oxide,was decomposed into the CoO_X@rGO-D and CoO_X@rGO-C using the above methods.CoO_X@rGO-D contains Co₃O₄ and CoO phase with smaller particle size and more uniform dispersion.The interaction between metal oxide particles and supporter is stronger.However,CoO_X@rGO-C only contains Co₃O₄ phase and its particles strongly agglomerate even directly detach from the supporter.CoO_X@rGO-D shows higher activity of oxygen reduction than CoO_X@rGO-C.The decomposition mechanism of cobalt precursor in DBD plasma is similar with potassium permanganate.In addition,the effects of oxygen-containing functional groups on the decomposition of metal precursors by DBD plasma was studied.