Modulating Electronic Structure of Atomically Dispersed Nickel Sites through Boron and Nitrogen Dual Coordination Boosts Oxygen Reduction

Atomically dispersed 3D transitional metal active sites with nitrogen coordination anchored on carbon support have emerged as a kind of promising electrocatalyst toward oxygen reduction reaction (ORR) in the field of fuel cells and metal-air cells. However, it is still a challenge to accurately modulate the coordination structure of single-atom metal sites, especially first-shell coordination, as well as identify the relationship between the geometric/electronic structure and ORR performance. Herein, a carbon-supported single-atom nickel catalyst is fabricated with boron and nitrogen dual coordination (denoted as Ni-B/N-C). The hard X-ray absorption spectrum result reveals that atomically dispersed Ni active sites are coordinated with one B atom and three N atoms in the first shell (denoted as Ni-B1N3). The Ni-B/N-C catalyst exhibits a half-wave potential (E-1/2) of 0.87 V versus RHE, along with a distinguished long-term durability in alkaline media, which is superior to commercial Pt/C. Density functional theory calculations indicate that the Ni-B1N3 active sites are more favorable for the adsorption of ORR intermediates relative to Ni-N-4, leading to the reduction of thermodynamic barrier and the acceleration of reaction kinetics, which accounts for the increased intrinsic activity.