Metal air battery because of its rich raw materials, high energy density, light, security, environmental protection and other advantages, and is known as the 21st century, one of the most promising green energy. However, looking for cost-effective oxygen reduction catalyst is the development of metal air battery is the key problem, but also restricts the metal air battery in electric vehicles and other fields widely used "bottleneck."

       Professor Wang Weichao of Nankai University and Professor Yao Yan of the University of Houston, have successfully used manganese-based mullite as catalyst for magnesium air battery. Compared with the traditional noble metal catalyst, the cost of the material is greatly reduced and can be stably operated in the neutral electrolyte. The excellent catalytic activity greatly improves the efficiency of the magnesium air battery. This is the first time that mullite materials have been used in oxygen reduction reactions.

       Metal air battery is a kind of special fuel cell which takes metal as fuel and produces redox reaction with oxygen in air. It uses oxygen in the air as the positive electrode active material and metal zinc (or aluminum and magnesium) as the negative electrode active material. Oxygen in the air can be continuously flow through the gas diffusion electrode to reach the reaction interface with the metal reaction of electric energy released. 

      However, in metal-air batteries, oxygen reduction (ORR) catalysts directly determine the efficiency of electrical conversion, battery costs and life expectancy. Traditional ORR catalysts are mainly precious metals and metal chelates. However, precious metals have limited reserves and cost is too high; the variety of metal chelate is less, and the preparation process is complicated and other factors restrict the application of these two kinds of catalysts. With the development of oxygen electrode technology and the need to reduce the cost of batteries, it is very important to find a kind of catalyst, which is cheap and has good catalytic activity for oxygen reduction, as one of the important topics in fuel cell research.

      In the alkaline condition, the metal surface can not passivate and the catalytic reaction can not be continued. The good work environment must be realized in the neutral solution, which poses a great challenge to the ORR catalyst design. 

      "Mullite is a class of ceramic materials." Almost no one thought about using it as a catalyst for metal-air batteries. "Wang said the idea stems from what he did four years ago to deal with diesel engine exhaust nitrogen oxides Research. He found in the experiment, nitric oxide into nitrogen dioxide in the process, the manganese-based mullite material showed excellent catalytic effect. The results published in 2012, "Science" magazine.

      "We believe that the interaction of manganese-based mullite materials with oxygen is critical and we anticipate that the catalytic processes involved in oxygen-related mullite materials may be applicable," Wang said.

      Based on such a bold vision, Wang has found a rich air battery R & D experience in the design of the University of Houston Professor Yao Yan, a joint research team. After a lot of experiments and theoretical research, they finally succeeded in the manganese-based mullite materials for the first time as a magnesium air battery ORR catalyst in the neutral solution of sodium chloride (NaCl) solution, the ORR reaction overpotential reached 0.78V, has Close to the performance of noble metal platinum catalyst (0.7 V), and the material stability is better than precious metals.

      "The first is a substantial reduction in cost. Previously used platinum, the price of grams of calculation, one gram is at least 200 yuan.Now use mullite to tons of counting.Secondly, it is more stable, you can repeat the reaction more, which Which means that the life of the battery is prolonged.Thirdly, this is the first application of the mullite material in the metal air battery, which opens up a new way for the new application of the mullite material in the electrochemistry.

      Preparation of manganese-based mullite catalyst and theoretical performance prediction by Wang Weichao task group completed. Professor Yao Yan group to achieve the application of manganese-based mullite catalyst for the design of magnesium air batteries, and prototype prototype button batteries. The output voltage of the prototype battery can drive a red LED lamp, indicating that the catalyst has a good catalytic activity, has a huge potential applications.

      It is understood that the study by the Central Organization Department, "thousands of young people", the National Natural Science Foundation of the project (21573117) and the United States National Natural Science Foundation (CMMI-1400261) support. The paper on the results of the collaboration has been published online by the world-renowned scientific journal, "Nano Energy". 

(China Daily Tianjin reporter station)