三维氮磷共掺杂石墨烯的制备及电催化氧还原性能研究

Synthesis of three-dimensional nitrogen and phosphorus co-doped graphene and its electrocatalytic oxygen reduction performance

氧还原反应(ORR)是燃料电池和金属-空气电池的阴极反应,其缓慢的动力学是目前掣肘燃料电池和金属空气电池发展的主要因素。为了使反应顺利进行,常常需要使用金属(包括贵金属和过渡金属)基催化剂,但这些催化剂存在价格高、稳定性差等缺陷。非金属原子掺杂的碳基催化剂近年来被认为是一种具有前景的ORR电催化剂。在此,使用单一前驱体磷酸三聚氰胺和氧化石墨烯经水热然后退火制备了三维氮磷共掺杂石墨烯材料(3DNPG)。通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等手段对3DNPG的结构与组成进行了表征。结果表明:3DNPG具有独特的三维网状结构、较大的比表面积(514.38m 2/g),特别是还具有非常高的N(15.53%)和P(6.61%)掺杂量。用作碱性溶液里ORR的催化剂时,其起始电位为0.994V,半波电位为0.817V,极限电流为5.34mA/cm^(2),在48h后电流密度保持率仍维持在99%,因此是一种兼具优异活性和循环稳定性的ORR催化剂,在燃料电池、金属-空气电池等领域具有非常重要的应用价值。

Oxygen reduction reaction(ORR)is a cathodic reaction in fuel cells and metal-air batteries,and its sluggish kinetics is the major obstacle to the development of these devices.Metal-based catalysts,including precious and transitional metals,are often used to facilitate the reaction,but their high cost and poor stability limit their practical application.Non-metal atom-doped carbon-based catalysts have emerged as promising alternatives to ORR electrocatalysts.In this study,a three-dimensional nitrogen-phosphorus co-doped graphene material(3DNPG)was synthesized by hydrothermal and annealing treatment using an exclusive precursor,melamine phosphate,with graphene oxide.The structure and composition of 3DNPG were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The 3DNPG exhibited a unique three-dimensional network structure,a large surface area(514.38m^(2)/g),and extremely high levels of N(15.53%)and P(6.61%)doping.As an ORR catalyst in alkaline solution,3DNPG showed excellent activity and cyclic stability,with an onset potential of 0.994V,a half-wave potential of 0.817V,a limiting current of 5.34mA/cm^(2),and a current density retention rate of 99%over 48h,making it great value for practical applications in fuel cells and metal-air batteries.