Mussel-Inspired Sequential Coating Strategy for High-Density CoNi Bimetallic Tubular Structured Magnetic Composites with Enhanced Catalytic Performance

Abstract The rational design of tubular nanostructures with controllable spatial distribution of bimetallic nanoparticles(NPs) is of vital importance for advancing high-performance catalytic systems, yet remains a significant synthetic challenge. To address this, we developed two synthetic routes to obtain one-dimensional (1D) tubular CoNi-based magnetic nanostructures through a combination of hydrothermal reaction, classical Stöber method, mussel-inspired coating, and carbonization strategy. Route 1 involves MoO3@CoNi-LDH microrods coated with SiO2 and subsequently with a polydopamine-Ni2+ (PDA-Ni2+) layer, followed by pyrolysis under nitrogen to yield CoNi@SiO2@NC-Ni composites; Route 2 employs MoO3@CoNi-LDH coated first with PDA-Ni2+ and then with SiO2, followed by thermal treatment to give CoNi@NC@SiO2 composites. Notably, our findings confirm that only Route 1 leads to the formation of both a high-coverage outer layer of Ni NPs and inner CoNi bimetallic NPs. Detailed characterization of the CoNi-based magnetic composites obtained via Route 1 revealed superior catalytic performance compared to Route 2, attributed to their unique structure and high density of Ni and CoNi NPs. These results demonstrate that this coating strategy is highly beneficial for the synthesis of CoNi-based bimetallic composites with 1D hollow structures, paving a novel pathway for preparing high-density bimetallic magnetic composites.