可充放锌空电池用过渡金属氧化物双功能催化剂研究进展

Advancements in the study of transition metal oxide bifunctional catalysts for rechargeable zinc−air batteries

近年来,可充放锌-空气二次电池因其高理论比能密度、高安全性、环境友好、低成本等优点,引起了广泛的关注,被认为是未来电网和电动汽车供电的可行选择之一.锌空电池中,氧还原反应和析氧反应催化剂的活性和稳定性对电池的能量密度、功率密度和寿命有重要影响,因此,开发高效、稳定的氧还原/析氧反应双功能催化剂已经成为一个重要研究方向.本文介绍了不同种类过渡金属氧化物催化剂的活性来源及其在锌空电池能量密度、充/放电电压、循环寿命等方面的表现,总结了当下研究现状中提高催化性能的策略和方法.

In recent years,rechargeable zinc-air batteries(ZABs)have attracted much attention owing to their high theoretical specific energy density,safety,and environmental friendliness.They are also considered a viable option for powering the grid and electric vehicles in the future.The activity and the stability of the bifunctional catalysts for the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)in ZABs remarkably influence the battery’s energy,power densities,and lifetime.Therefore,developing efficient and stable bifunctional catalysts is an important research direction.Previously,precious metal catalysts such as Pt/C,Ir/C,and Ru/C have been used to design efficient ORR and OER electrocatalysts.However,these electrocatalysts possess several issues,including limited natural abundance,high metal sintering and catalyst detachment rates from supports,and poor bifunctional activity,which limit their practical applications.As potential catalysts,nonprecious transition metal oxides exhibit the prominent advantages of manifold compositions,multiple valence states,environmental friendliness,high durability and abundance,and varying structures.Their disadvantages include poor electrical conductivity and a limited surface area.To address the abovementioned issues,current general research focuses on compounding transition metal oxides with carbon materials or other conductive substrates to simultaneously increase t heir specific surface area and electrical conductivity and control their morphology to expose more active sites.Furthermore,the intrinsic activity of the transition metal oxides must also be regulated through the most commonly used activity regulation methods(e.g.,heteroatom doping and defect engineering).For example,perovskite and spinel-type transition metal oxides must meet a specific eg orbital occupancy to achieve the best bifunctional activity.Therefore,improving the catalytic performance requires the A-and B-site atom substitution with other alkaline and rare earth or transition metals or the introduction of oxygen vacancies to adjust the electronic structure.Spinel-and perovskite-type transition metals and manganese oxides are the research objects used in this work.The activity sources of different types of transition metal oxide catalysts and their performances in energy density,charge/discharge voltage,and cycle life of zinc-air batteries are introduced herein.The strategies and methods used to improve the catalytic performance of transition metal oxides in current research are summarized.Finally,the future development of transition metal bifunctional catalysts for oxygen reduction and evolution reactions is prospected.