Co0.85Se nanoparticles armored by N-doped carbon layer with electronic structure regulation functions: An efficient oxygen evolution electrocatalyst

In this work, with the assistance of polymeric nonionic surfactant Pluronic F127, 2D nanosheets glycerol cobalt self-assembled into the ball-flower structure composites ([email protected]). Then, [email protected] is coated by polydopamine (PDA) to form [email protected]@PDA. After the calcination with Se powder, [email protected]@PDA is transformed into the ball-flower hierarchical structure Co0.85Se-NC/C, in which Co0.85Se nanoparticles are coated with nitrogen doped carbon (NC). The Co0.85Se nanoparticles anchored on the NC can avoid the aggregation, maintain structure stability and expose more electrocatalytic active sites for oxygen evolution reaction (OER). Specially, Co0.85Se-NC/C-750 shows a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH that is even lower than IrO2 and most of the reported Co-based catalysts. Besides, the theoretical calculations by density functional theory (DFT) suggest that NC could tailor the electronic structure of Co0.85Se, leading to optimized free energy change (ΔG) of the speed-controlled step and density of states (DOS).