Adjacent-Confined Pyrolysis for High-Density Phase Boundaries in Mo₂C Nanosheets to Boost Oxygen Evolution

Heterostructure or doping engineering on Mo₂C by coupling with transition metal nanoparticles/atoms can optimize catalytic activities for oxygen evolution reaction (OER). However, the intrinsic catalytic activity of Mo₂C is not fully stimulated at the atomic level, which is challenging. Herein, an adjacent-confined pyrolysis strategy to manipulate the intrinsic electronic structure of Mo₂C directly is reported. During the nucleation and growth of Mo₂C, the replacement of Mo atoms by adjacent Ni atoms induces the generation of high-density phase boundaries (PBs) with alternating face-centered cubic (fcc) and hexagonal close-packed (hcp) hetero-phase. The lattice deformity in PBs affords an ultrahigh density of active sites, endowing Mo₂C nanosheets with excellent OER activity and superior stability. Theoretical calculations reveal that introduced Ni atoms activate the adjacent Mo sites and optimize the thermodynamic reaction energetics for enhanced OER activity. The work offers a general adjacent-confined pyrolysis strategy to achieve PBs-controlling in Mo₂C nanosheets for catalytic application and beyond.