Nanostructured CoxNi1−x bimetallic alloys for high efficient and ultrafast adsorption: experiments and first-principles calculations

Abstract

Use change of composition and surface defects of Co_xNi_1−x bimetallic alloy prepared at room temperature to improve their adsorption capabilities. Congo red (CR) was used to evaluate the Co_xNi_1−x bimetallic alloys' adsorption capabilities. At 100 mg L⁻¹ of initial CR concentration, 1000 mg g⁻¹ of adsorption capacity could be achieved by the Co_xNi_1−x nanoparticles in time range of 2 to 20 minutes. Here, Co_0.6Ni_0.4 bimetallic alloy shows the best adsorption efficiency, reaching 1000 mg g⁻¹ at 2 min. Furthermore, density functional theory (DFT) simulations were introduced to understand why Co_0.6Ni_0.4 bimetallic alloy had better adsorption efficiency than monometal Co and Ni. Based on DFT simulations, large surface energy, low work function and high reducibility of Co_0.6Ni_0.4 bimetallic alloy may be responsible for its high adsorption capability and efficiency. By a further investigation on surface electronic structure, it can be found that the chemical composition and surface defects have influences on d-band center, and a proper d-band center may facilitate to both the high rate of electrons transfer to adsorbate and removal of surface intermediate. The combination of experiment and DFT simulations proved that the adsorption ability of Co_0.6Ni_0.4 bimetallic alloy is better than that of single metal, and shows promise as commercial scale magnetic adsorbent.