Preparation of Nd-reinforced N-doped Cu7S4 rich in sulfur vacancies for supercapacitors

Introducing sulfur vacancies in transition metal sulfide-based electrode materials is an effective way to improve the electrochemical energy storage of the materials. Nd-reinforced N-doped Cu₇S₄ (Nd@N-Cu₇S₄) composite material, supported on nickel foam (NF), is synthesized by regulating the doping of Nd into the N-doped Cu₇S₄ materials. Regulating on the number of doped Nd atoms can change the concentration of sulfur vacancies produced in the N-doped Cu₇S₄ material. After introducing sulfur vacancies, the diffusion rate of ions and the number of reactive sites in the material are enhanced by altering the distribution of local electron concentrations around the sulfur vacancies during the electrochemical reaction process. This increases and improves the electrochemical energy storage of the Nd@N-Cu₇S₄ material. Theoretical calculations are carried out to study the influence of the generation of sulfur vacancies on the material structure. The Nd-reinforced N-doped Cu₇S₄ (Nd@N-Cu₇S₄) composite electrode exhibits a higher energy storage capacity than existing copper sulfide-based electrode materials and other ion-doped sulfides. To further investigate the practical application of Nd@N-Cu₇S₄/NF, a liquid-phase supercapacitor is constructed featuring a wide operational potential window of 1.8 V. This device utilizes Nd@N-Cu₇S₄/NF as the negative electrode and Nd@N-Cu₇S₄/CF (carbon felt) as the positive electrode, with 1 M NaOH serving as the electrolyte. The assembled supercapacitor demonstrates high energy density, emphasizing the potential of the Nd@N-Cu₇S₄/NF electrode in high-performance energy storage applications. These findings suggest that the Nd@N-Cu₇S₄/NF composite is a promising candidate for advancing the development of next-generation supercapacitors.