一锅法制备Fe_(2)O_(3)@Fe-N-C氧还原电催化剂及其锌-空气电池的性能研究

One-Pot Synthesis of Fe_(2)O_(3)@Fe-N-C Oxygen Reduction Electrocatalyst and Its Performance for Zinc-Air Battery

在金属空气电池和燃料电池阴极上的氧还原反应(ORR)对相关电化学能量转换装置的整体性能有重要影响,金属-氮-碳催化剂有望替代传统的商业Pt-C成为新一代ORR电催化剂。本文通过简便的一步热解工艺合成了具有Fe-N_(x)活性位点和Fe_(2)O_(3)纳米颗粒共存的电催化剂,Fe_(2)O_(3)@Fe-N-C-1000催化剂在0.1 mol·L^(-1) KOH溶液中表现出良好的ORR活性,半波电位为0.84 V,应用在锌-空气电池中时也具有可以和商业Pt-C媲美的性能,能量密度为88.3 mW·cm^(-2),同时和Pt-C相比具有更好电化学稳定性,表现出优良的ORR应用潜力。

Oxygen reduction reaction(ORR)plays a profound role in determining cathode performance in metal-air batteries and fuel cells.Owing to its inherently sluggish kinetics,high-performance ORR catalysts which favors the scissoring of O-O bond and formation of O-H bond are a requisite.In this regard,Pt has been explored as the most efficient ORR electrocatalysts.Nevertheless,due to its expensiveness,the usage of Pt catalysts represents one of the major sources of cost in those energy conversion devices.Thus,the development of alternative ORR electrocatalysts with minimized Pt utilization has been widely pursued over the past few decades.Metal-nitrogen-carbon catalysts are expected to replace traditional commercial Pt-C and become a new generation of ORR electrocatalyst.In this paper,using a commercial chain hollow carbon nanosphere(ECP-600JD)with high specific surface area and high conductivity as carbon source and template,Fe_(2)O_(3)@Fe-N-C nanocomposite was prepared by a straightforward one-step pyrolysis method as a high-performance ORR electrocatalysts in alkaline media,and its structural characteristics and catalytic performance have been systematically studied.Such a nanocomposite was characterized with large external surface area(467.8 m2·g-1),high electronic conductivity,as well as the co-existence of Fe-N_(x) active sites and Fe_(2)O_(3)nanoparticles.Owing to its compositional and structural merits,the optimal Fe_(2)O_(3)@Fe-N-C catalyst showed good ORR activity in 0.1 mol·L^(-1) KOH solution,with its half-wave potential being 0.84 V.When used in zinc-air batteries,the open circuit voltages of the battery assembled by Fe_(2)O_(3)@Fe-NC-1000 and Pt-C were 1.51 V and 1.42 V,respectively.It also demonstrates better rate performance than Pt-C,which can be attributed to the large specific surface area that can provide excellent mass transfer ability under high current density,and its own excellent electrical conductivity was also extremely important.According to the mass of zinc consumed,the specific capacity of the zinc-air battery was calculated,and the specific capacity of the battery assembled with Fe_(2)O_(3)@Fe-NC-1000 could reach 776.8 mAh·gZn-1,while the specific capacity of Pt-C under the same conditions was 691.9 mAh·gZn-1.The polarization curve and power density of the catalyst were also obtained.The peak power density of zinc-air battery with Fe_(2)O_(3)@Fe-NC-1000 as the cathode reached 88.3 mW·cm^(-2),while the peak power density of the battery with Pt-C as the cathode was 76.8 mW·cm^(-2).Our research provides a straightforward and easily scalable approach towards the pursuit of high-performance ORR electrocatalysts.