Advanced electrocatalysts with Dual-metal doped carbon Materials: Achievements and challenges

Dual-metal site is more than simple double of the single atom, which has particular functionalities that help to promote electrocatalytic performance utilizing the synergistic effect. In the past few years, tremendous progress has been achieved in this field, although the research of dual-metal site is still in the developing stage. In this review, the preparation strategies and characterization techniques of dual-metal sites are summarized, which always develop hand-in-hand. Currently the main task is on the synthesis to achieve precise site-control. The reason is that the synergistic effect demands adjacent metal coupling, either in Homonuclear or heteronuclear form, yet different metal couples may exist with different local coordination configurations, i.e., (MN3)-N-I-(MN3)-N-II or (MN4)-N-I-(MN4)-N-II, posing challenges in characterization. Theoretical modeling and simulation, which are indispensable tools to elucidate the nature of atomic level catalyst, are addressed here. These techniques are essential for screening potential candidates and rationalization of reaction mechanism. Here, we focus on the critical roles of charge difference, spin polarization and the promise to break scaling relationship via providing two reaction centers, which are unique traits for dual-atom sites. Finally, perspective on future challenges and opportunities are discussed.