General Synthesis of Hierarchically Macro/Mesoporous Fe,Ni-Doped CoSe/N-Doped Carbon Nanoshells for Enhanced Electrocatalytic Oxygen Evolution.

Constructing hierarchical porosity and designing rational hybrid composition are effective strategies for enhancing the electrocatalytic performance of hybrid catalysts for electrochemical energy conversion. Here, we develop a multistep "molecule/ion-exchange" strategy toward the synthesis of hierarchically macro/mesoporous Fe,Ni-doped CoSe/N-doped carbon nanoshells with tunable pore structures and compositions. Polystyrene (PS)@Co-based amorphous coordination polymer (Co-CP) core-shell particles with hierarchically macro/mesoporous nanoshells are first prepared by ligand-molecule-exchange etching of the outer layers in PS@Co-based metal-organic framework precursors. Afterward, a liquid-solid dual-ion-exchange reaction of PS@Co-CP particles with [Fe(CN)] and [Ni(CN)] ions leads to the formation of PS@Co-CP/Co-Fe Prussian blue analogue (PBA)/Co-Ni PBA particles, which are further transformed into hierarchically macro/mesoporous Fe,Ni-doped CoSe/N-doped carbon particles via a vapor-solid selenization reaction. Moreover, this approach could be extended to synthesize different hierarchically porous core-shell composites with various morphologies and tailored compositions. Because of their unique hierarchically porous nanoarchitecture, these Fe,Ni-doped CoSe/N-doped carbon particles with optimized composition show enhanced performance for electrocatalytic oxygen evolution.