Effect of flower-like Ni/C nanocrystal on electrochemical hydrogen storage properties of Co-P alloy

The flower-like Ni/C nanocrystal were synthesized by solvo-thermal method, and Co-P alloy was prepared by mechanical alloying method. Finally, different proportions of Ni/C nanocrystal and Co-P alloy were mixed by ball milling method to form the Co-P + Ni/C composites. Compared with the pristine alloy, the Co-P + Ni/C composite electrode shows better discharge capacity and cyclic stability. When the weight ratio of Ni/C nano crystal reached 5%, the maximum discharge capacity of the Co-P + Ni/C composite electrode reached 635.8 mAh/g at a discharge current density of 30 mA/g, and its capacity retention rate reached 66.3% after 50 cycles. Linear polarization, electrochemical impedance spectroscopy and potentiometric polarization tests of the Co-P + Ni/C composites and Co-P alloy were caried out. The nickel particles in the flower-like Ni/C nanocrystal showed excellent electrocatalysis, and the special lamellar structure of Ni/C nanocrystal could increase the specific surface area of the alloy and provide more active sites for hydrogen adsorption, thus improving the discharge capacity of the electrode. The flower-like Ni/C nanocrystal coated on the surface separates the electrolyte from the alloy and improved the corrosion resistance of the alloy. In addition, the special lamellar structure and excellent electrical conductivity of Ni/C nanocrystal enhanced the exchange current density of the composite electrode and reduced the charge transfer resistance. Therefore, the unique structure and electrocatalysis of flower-like Ni/C nanocrystal can effectively improve the electrochemical properties of Co-P alloy. This work presents a simple and feasible method to improve the electrochemical hydrogen storage performance of Co-P alloy by adding Ni/C nanocrystal to the alloy by mechanical alloying.