The Synthesis And Performances Investiment Of Several Non-platinum Electrocatalyst For Oxygen Reduction Catalysts In Alkaline Environment

Developing renewable and sustainable energy production such as fuel cells which are clean and compatible with high-efficiency renewable energy represents one of the major development direction of energy in the twenty-first century.Recently,anion exchange membrane fuel cells?AEMFCs?get great attentions because of the progress of alkaline membranes and the advantage of low cost.The catalyst is needed for accelerating electrochemical energy conversion processes such as oxygen reduction reaction?ORR?which is a sluggish process involving multiple electron transfer is central to fuel cells.Although there are many electrocatalysts that are stable in base,platinum and its alloy remains the most active and stable for ORR.However,because of scarcity and uneven distribution of platinum,which result in expense and long-term instability.The discovery and development of efficient and cost-effective such as platinum-group-metal?PGM?-free anode and cathode catalysts for use in FC is fundamental in the future.Here,we develop several kinds of electrocatalysts and kindly investigate their structure,performances and their relationship.We get some main conclusions as follows:?1?We directly synthesis of highly porous P,N co-doped nanocarbon by simply carbonization the mixture of Phosphoric acid,pentaerythritol and melamine.The obtained sample deliver a half-wave potential of 0.87 V vs.RHE for oxygen reduction reaction in alkaline solution,approaching the commercial Pt/C catalyst.Through comparative experiments,it was found that the addition of KOH at the synthesis stage can not only promote the formation of micropores and mesoporous structures leading to an increase in the specific surface area of the catalyst,but also an increase in the formation of graphitized carbon leading to improve the stability of the catalyst.?2?We develop an iron-based electrocatalyst by carbonization the mixture of glucose,melamine,zinc chloride and Fe C l₃.We found that Zn C l₂ can function as a catalyst to direct formation of the carbon nanotube.At the same time,it can also be used as a pore-forming agent to cause the formation of abundant lattice defects in the carbon matrix through the evaporation of Zn atoms at high temperatures.These defects can trap iron atoms firmly to avoid there formation of iron carbide or iron particles.The as formed catalysts show a platinum-like catalytic activity in terms of half-wave potential in alkaline solution.The half-wave potential of the catalyst is 0.89 V in 0.1 M KOH solution,which is comparable to commercial Pt/C catalysts and has higher stability than commercial Pt/C.?3?Silver is stable in alkaline solution,but it delivers low catalytic activity for oxygen reduction reaction.Here,we developed an in-situ electrochemical activation method to modify the surface of the catalyst,which greatly improved the activity of the silver catalyst.The half-wave potential after activation reaches 0.865 V which is close to Pt/C catalyst,and it is increased by nearly 135 m V compared 0.73 V for the initial silver electrode.Further investment reveal that the activation process creates high-index crystal surface,which enhances the adsorption of oxygen molecules and their intermediate species on silver,which leading to the high catalytic activity of silver.