Facile fabrication of ultrafine CoNi alloy nanoparticles supported on hexagonal N-doped carbon/Al2O3 nanosheets for efficient protein adsorption and catalysis

Carbon supported bimetallic nanoparticles (NPs) hold great potential in developing high-performance catalysts and adsorbents. Herein, we demonstrate a facile strategy including a conventional hydrothermal method, Ni2+ mediated dopamine polymerization and post-calcination treatment for the synthesis of C-CoNi/Al2O3 bimetallic composites. Remarkably, high annealing treatment favors the construction of sandwich-like nanostructures and the formation of outer bimetallic CoNi NPs. The sheet-like nanostructures with the magnetic properties of CoNi NPs possess a relatively large surface area and can be easily collected and recovered from the reaction solution with an external magnet. Benefiting from compositional and sheet-like structural advantages, these C-CoNi/Al2O3 nanosheets exhibit better catalytic and adsorption properties toward 4-NP reduction and His-rich protein adsorption compared with other Co-based composites such as Co/Al2O3 and C-Co/Al2O3. Such an effective strategy could be extended to large-scale synthesis of uniform and stable multi-metallic composites.