Co75Pt25 alloy nanoparticles: A class of catalyst for the catalytic reduction of 4-nitrophenol with enhanced activity and recycling

Highlights: • The Co_xPt_100-x (x = 25, 35, 50, 65, 75) alloy catalysts are synthesized by a facile method. • The Co_xPt_100-x (x = 25, 50, 75) alloy catalysts are superpara-magnetic with a small size. • The Co₇₅Pt₂₅ alloy catalyst exhibits excellent catalytic performance for the reduction of 4-NP to 4-AP. • The Co₇₅Pt₂₅ alloy catalyst can be separable easily and used four times. -- Abstract: We report a facile one-step, co-chemical reduction controlled synthesis of Co_xPt_100-x (x = 25, 35, 50, 65, 75) alloy nanoparticles (NPs). Alloy NPs with Co to Pt atomic ratios of 25/75, 50/50 and 75/25 were found to exhibit a pure phase and superpara-magnetism with a small NP size distribution. The saturation magnetization for Co₇₅Pt₂₅ NPs (55.17 emu/g) was highest than that for Co₂₅Pt₇₅ NPs (47.58 emu/g) and Co₅₀Pt₅₀ NPs (32.38 emu/g), confirmed the best magnetic response of Co₇₅Pt₂₅ NPs. Furthermore, the average crystallite sizes for Co_xPt_100-x (x = 25, 50, 75) alloy NPs is 5.72 nm, 5.43 nm and 5.6 nm, respectively. The observation of an obviously reduced catalytic reduction time and increased rate constant confirmed that the Co_xPt_100-x (x = 25, 50, 75) alloy NPs exhibit intensive performance for the catalytic reduction of 4-nitrophenol (4-NP). Moreover, compared with Co₂₅Pt₇₅ and Co₅₀Pt₅₀ alloy NPs, the Co₇₅Pt₂₅ alloy NPs exhibit short reaction times for catalytic reduction due to their stability in aqueous solution and short induction time. The recycling ability of the alloy catalysts was certified with high yields in four reaction cycles.