Phase-control synthesis and catalytic property of magnetic Ni@NixPy core-shell microstructures
Highlights: • Ni@Ni{sub x}P{sub y} core-shell microstructures are synthesized by a low-temperature phosphidation route. • The initial Ni/NaH{sub 2}PO{sub 2} molar ratio can strongly affect the phase of the final product. • Ni@Ni{sub x}P{sub y} microstructures present good catalytic activity for the reduction of 4-nitrophenol. • The catalytic property of Ni@Ni{sub x}P{sub y} microstructures presents markedly phase-dependent features. - Abstract: Magnetic Ni@Ni{sub x}P{sub y} core-shell microstructures were successfully synthesized by a simple low-temperature phosphidation route, employing Ni nanospheres as the initial nickel source, NaH{sub 2}PO{sub 2}·H{sub 2}O as the phosphorus ion source. The phosphidation reaction was carried out in N{sub 2} atmosphere at 300 °C for 2 h. Experiments showed that the initial Ni/NaH{sub 2}PO{sub 2} molar ratio could strongly affect the phase of the final product. When the Ni/NaH{sub 2}PO{sub 2} molar ratio of 1:2.77 was used, hexagonal Ni{sub 2}P phase was obtained; while the Ni/NaH{sub 2}PO{sub 2} molar ratio was 1:5.54, hexagonal Ni{sub 5}P{sub 4} phase was produced. It was found that the magnetic properties of the products gradually decreased with the conversion from Ni nanospheres, to Ni@Ni{sub 2}P and to Ni@Ni{sub 5}P{sub 4}. Moreover, initial Ni nanospheres, Ni@Ni{sub 2}P and Ni@Ni{sub 5}P{sub 4} core-shell microstructures presented outstanding catalytic activities for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in excess NaBH{sub 4} solution. Ni@Ni{sub 5}P{sub 4} core-shell microstructures owned the best catalytic activity.