| dc.description.abstract | This research focuses on the development of air cathodes for metal-air batteries. We synthesized composite catalytic materials to enhance the battery performance, especially for secondary metal-air battery applications due to bifunctional air cathode. The composite catalytic materials are composed of XC72 carbon black, α-、β- or γ-MnO2 and different weight ratio of gold nanoparticles (Au NPs), as the catalytic layer in the air cathode. By using P123 as a structure-directing reagent, the morphologies and the specific surface area of this composite material can be further tuned.
Their morphologies、crystalline phase、surface area and electrochemical performance were characterized by SEM、XRD、BET and Potentiostat. The morphologies of α-、β- and γ-MnO2 are rod-like and the XRD patterns are consistent with JCPD cards. The BET surface area of α-、β- and γ-MnO2/XC72 are 95.38、73.03 and 85.76 m2/g, respectively The surface area of α-MnO2/XC72 increased from 95.38 m2/g to 123.8 m2/g by adding P123.
It was found that the electrochemical performance of α-MnO2 was the best as air electrode. LSV measurements indicated that the current density of α-MnO2/XC72 was -17.4 mA/cm2 at -0.7 V, whereas β- and γ-MnO2/XC72 were -14.6 and -5.68 mA/cm2 at the same bias. Meanwhile, gold nanoparticles as additives increased the cathodic current density and lowered the overpotential. The current density of α-、β- and γ-MnO2/XC72 were -38.86、-17.7 and -31.64 mA/cm2 at -0.7 V by adding gold nanoparticles (weight ratio 4 : 1), respectively.
Zn-air battery discharge test showed that the discharge voltages of α-MnO2, β-MnO2 and γ-MnO2/XC72 were 1.088 V, are 1.050 and 1.072 V at 50 mA/cm2, respectively. The discharge voltage of α-MnO2/XC72 increased to 1.15 V at 50 mA/cm2 by adding P123, perhaps due to the increase in specific surface area. The highest discharge voltage of α-MnO2/XC72 is 1.243 V at 50 mA/cm2 by adding P123 and Au nanoparticles (weight ratio 2：1).
It is evident that this composite air cathode, MnO2/Au NPs, provides good catalytic activities, which could be a good candidate for various types of metal air battery in the future. | en_US |