A Generic Conversion Strategy: From 2D Metal Carbides (M_xC_y) to M-Self-Doped Graphene toward High-Efficiency Energy Applications

This study first presents a subtle thermal-chlorination strategy for a universal transformation of abundant 2D metal carbides (M_xC_y, e.g., Cr₃C₂, Mo₂C, NbC, and VC) to 2D graphene and M-self-doped graphene (MG). The as-obtained MG endows a transparent sheet architecture of one to four atomic layers. Simultaneously, MG with different M amounts is synthesized by tuning the chlorination parameters. Among them, the novel and representative Cr-self-doped graphene with optimal Cr amount (4.81 at%) demonstrates the outstanding electrochemical performance. It presents an energy density of 686 W h per kg electrode and a power density of more than 391 W per kg electrode as anode material of Li ion batteries, and four-fold activity against the commercial iridium oxide electrode toward oxygen evolution reaction as well as a comparable oxygen reduction reaction performance to the commercial platinum catalyst. Moreover, this method is readily scalable to produce graphene and MG electrode materials on industrial levels.